About This Guide

Author. Steve Wolf. Expert witness in firearms, pyrotechnics, fire, stunts, rigging, climbing systems, industrial accidents, and entertainment production safety. Thirty-five years of production and forensic work. Columbia University. Eleven patents. Twenty books.

For. Working expert witnesses in every discipline: engineers, physicians, accident reconstructionists, fire investigators, safety professionals, human factors specialists, economists who visit sites, and anyone whose opinion rests on something they saw and now have to prove. It assumes you have never held a camera. It does not assume you are a beginner at anything else.

Contents. Forty chapters in six parts. 602 checklist items across forty field checklists. One hundred forty-five numbered tips. Eight appendices, including templates, a glossary, and a list of the standards that do not exist.

Covers. Camera and lens fundamentals for a non-photographer. Light, color, and scale. Field protocol for scenes, injuries, parts, fire, water, height, darkness, and night. Drone work. Photogrammetry and laser scanning. Video, high-speed video, and surveillance recordings. Audio for witness interviews. Metadata, hashing, chain of custody, and archival storage. Authentication under Federal Rule of Evidence 901 and 902. Discovery, spoliation, and where the law lets you point a camera. Rule 403, the new Rule 107, animation versus simulation, courtroom display, and testifying about your own images.

Does not cover. Writing the report, negotiating the engagement, or surviving cross examination generally. Those belong to Being a Great Expert Witness. Building the underlying investigation belongs to Investigating Personal Injury Cases. This book stops at the moment the image goes into the report.

Currency. Revision 2026-07. Federal Rule of Evidence 702 current through the December 1, 2023 amendment. Federal Rule of Evidence 107 current through its December 1, 2024 effective date. Standards and technical guidance current through July 2026.

Disclaimer

This book is a guide for expert witnesses, attorneys, and claims professionals. It is not legal advice, and it is not a substitute for the judgment of retaining counsel. Rules of evidence, procedure, consent, privacy, and access vary by jurisdiction and change over time. Confirm every rule, statute, and standard against a primary source before you rely on it in a matter. Admissibility is for the court. Weight is for the jury.

Introduction: The Photograph You Did Not Take

Imaging problems in litigation can begin with capture, preservation, processing, or presentation. A photographer's choices limit what later reviewers can evaluate, especially if the scene has changed. Ask what the camera recorded, what it missed, what the imaging process altered, and what evidence supports those distinctions.

An expert's opinions require support. Photographs can document observations, but the opinions may also depend on measurements, records, testing, and witness accounts.

An expert can photograph the apparent points of interest and overlook a wear pattern, a light fixture, or the floor between two frames. If the scene changes before those omissions become apparent, a return visit may not recover the missing information. Evaluate the photographs alongside other surviving evidence rather than treating the images as the only record of what happened.

A later copy of a file cannot recover detail the camera never recorded.

Four ideas run through everything in this book.

First, treat the camera as an instrument, not just a convenience. For measurements, identify the camera and lens, document the configuration and procedure, and evaluate the error relevant to the measurement. A photograph used only to document appearance has different requirements from one used to calculate a dimension.

Second, capture at examination quality when practicable, because later analysis may require more detail than the initial assignment. File quality alone does not make an image suitable for measurement. Geometry, scale, focus, and the proposed analysis also matter.

Third, preserve and present images as carefully as you capture them. Authentication, discovery obligations, and readable displays affect how the images can be used. A failure in one stage can limit a particular use without making every other use of the images worthless.

Fourth, there is no certificate that makes your imaging reliable. The standards body that once governed forensic photography is defunct, its successor publishes guidance rather than binding standards, and there is no published American national standard for scene photography as of this writing. That is not a loophole. It is a burden. Under Federal Rule of Evidence 702 you will prove reliability with a documented, reproducible method that you can name and defend, and that is the discipline this book teaches.

Missing photographs can leave questions unanswered, particularly after a scene changes. Record gaps in coverage and consider whether measurements, other images, or other evidence can address them.

Take the picture. Take the one you think is pointless. Then read the rest of this book so the ones that matter hold up.

How to Use This Book

Each chapter opens with the reasoning and closes with a working checklist. The checkboxes work on screen and print cleanly on paper. Read the chapters once. Use the checklists every case.

Part One frames the work and tells you the honest state of the standards. Part Two teaches camera craft from zero, for a reader who has never held one. Part Three is field protocol, scene by scene and difficulty by difficulty. Part Four covers video, audio, and testing. Part Five covers preservation, authentication, discovery, and access. Part Six covers presentation and testimony.

If you are on a plane tonight and shooting a scene tomorrow, read Chapters 1, 6, 12, 14, and 15, print the checklists from Chapters 14 and 15, and read the rest when you get home.

Three kinds of callout appear throughout. A Practice Tip gives a concrete action. A Caution flags an exposure in discovery, on the stand, or in the record. A Field Note is my own policy or something I learned the expensive way.

One hundred forty-five numbered tips are scattered through the chapters in chapter-and-tip format, so tip 12.3 is the third tip in Chapter 12. All of them are collected in Appendix E. All forty checklists are consolidated in Appendix A, in the order a case runs, and are also published as a separate downloadable pack you can print, fill out, and put in the file.

Nothing in this book requires you to become a photographer. It requires you to become an expert who can prove what the camera did.

Part One. The Frame

Chapter 1: Photographing to Document

Photographs taken as memory aids may omit the scale, context, or detail needed for later analysis.

The difference does not show up on the day you shoot. It shows up eighteen months later, in a conference room, when opposing counsel slides a print across the table and asks you to identify the dark object at the lower left of the frame. If you photographed to remember, you say you believe it was a bracket. If you photographed to prove, you open the frames that show that bracket from three distances with a scale in its plane, and you say what it is, how large it is, and where it sat relative to everything else in the room.

The note you take and the exhibit you build

Two kinds of images come out of an expert's bag. The first is the memory aid: a visual note, taken so that you can reconstruct your own thinking later. It is aimed at you. The second is the exhibit: an image built from the first press of the shutter to be handed to a stranger who was not there, who does not trust you, and who is being paid to find the seam in your work. It is aimed at the record.

A memory aid may lack the detail needed for a proposed analysis. Automatic settings may still appear in metadata, but the file should be checked. Missing scales or orientation frames can limit measurements and scene placement. An unchecked clock or a transfer that removes metadata can complicate provenance. Assess each limitation against the intended use rather than rejecting the image solely because it began as a visual note.

What an evidentiary image has to do, in order

An evidentiary image must support its stated use. It may document a condition, support a measurement, or help explain an observation. Not every image can serve all three purposes. Preserve the record and avoid capture or presentation choices that favor persuasion over accuracy.

Address authentication before relying on an image as evidence. If the proposed use includes measurement, explain the method and its limitations. Check that the presentation communicates the relevant information without misleading the viewer. The sequence of objections and the court's ruling will depend on the proposed use and the applicable rules.

The standards body splits every photograph into two classes

The Scientific Working Group on Digital Evidence, the standards body whose current documents govern this work, draws the same line in different words. Its 2025 document on image categories in forensic science divides everything a camera produces into two classes. Documentation images record appearance, condition, or location and are not intended for scientific analysis; the working group accepts a file format with minimal compression for those. Examination quality images are intended for expert scientific analysis and comparison, and for those the working group requires a file format with lossless or no compression, meaning a raw file or the Tagged Image File Format, at the highest resolution the device offers.

Read the two definitions again and you will see the trap. The category is assigned by what the image is later used for, and you do not know at the scene what your images will later be used for. The photograph you took to show where a ladder was standing becomes, four months later, the only image that shows the foot of that ladder against the floor at all, and now somebody wants to measure the angle. It was captured as documentation. It is being asked to serve as examination.

1.1: Capture at examination quality when practicable, because an image taken for documentation may later be considered for analysis.

Higher-quality capture preserves more options for later analysis. It also requires storage, suitable equipment, and a procedure that records scale and geometry when needed. Compression can limit an analysis, but assess the actual file and proposed use before concluding that an opinion cannot be supported.

Forty sharp photographs and no method behind them

An expert arrives at deposition with forty sharp, well-exposed phone photographs. The expert cannot identify the focal length, camera orientation, or processing used in several frames. The available copies passed through a cloud photo library and a text thread, and their creation dates match the day counsel requested them. These gaps complicate measurement and provenance questions. They do not establish that the images have no documentary value.

Nothing in that deposition was about photography. All of it was about method, and the expert had none.

Decide what question the frame answers before you shoot

Decide, before the shutter goes, what question the frame should answer. A visual note can serve as a memory aid. An image intended for evidence needs a preserved original and a documented method appropriate to its use. Add a scale when dimensions matter and record the context needed to understand the frame.

1.2Before each frame, name the question it answers. If you cannot name one, take it anyway and write down that you could not.

1.3Photograph the thing you are certain is irrelevant, because relevance is decided by people who were not standing where you were standing.

Where this book stops and the report begins

What you do with these images after they are made, how they enter your report, and how you testify from them, also belongs to Being a Great Expert Witness. Careful writing should identify what each image supports and what it does not. Other evidence may address gaps in the photographic record.

Chapter 1 Checklist: The Two Kinds of Image

Chapter 2The Camera Is a Measuring Instrument

A camera is a measuring instrument that happens to make pictures.

No engineer would accept a torque figure from a colleague who said he tightened the bolt until it felt about right. No chemist would accept a concentration from an instrument nobody had calibrated, run against a known standard, or documented. Yet experts hand over photographs every day with no stated settings, no verification of any kind, and no written procedure, and expect those photographs to carry measurements.

The three questions that make a camera an instrument

Calibration, repeatability, and documentation help evaluate a camera-based measurement. Identify the quantity being measured, test performance for the intended use, and record enough detail for another qualified person to assess or repeat the procedure. A weakness in one area requires evaluation; it does not erase the evidence available in the others.

Method and equipment both affect the proposed use

Evaluate the equipment and the method together. Camera price and manual exposure do not establish admissibility. A documented procedure helps explain an image, while resolution, exposure, geometry, preservation, and the intended use determine which conclusions the image can support.

The oldest rule in this literature is reproducibility

The oldest published statement of this principle in the American forensic imaging literature comes from the Scientific Working Group on Imaging Technology, the body that carried this field before it was absorbed into the current structure. Its Section 11, on documenting image enhancement, rests on four operative principles. The original file must be preserved. The documentation must satisfy the legal requirements for introducing forensic images in a court of law. The documentation must be sufficient to allow other professionals to understand what was done and produce comparable results. And the practices apply regardless of the tools and devices used.

Reproducibility matters alongside accuracy and resolution. Another professional should be able to understand the procedure and obtain comparable results, but a repeatable error remains an error.

The current body, the Scientific Working Group on Digital Evidence, says the same thing in operational language. Its image processing guidelines require that steps be recorded "in a manner sufficient to permit a comparably trained person to understand the steps taken, the techniques used, and to extract comparable information from the image." That is the same test, restated for digital work, and it is the sentence I would want read aloud at any hearing about my own imagery.

Work on duplicates and leave the originals alone

The working group's 2025 document on maintaining the integrity of imagery adds the handling rules that make reproducibility possible. Images are stored in an unaltered state. All examination and processing happens on duplicates, never on originals. The duplicate is verified against the original by hash comparison before any processing begins, and processed imagery is then treated as derivative evidence carrying its own integrity requirements. Hashing is performed before and after any copy operation and again before storage. Storage means physical security, logical security, and redundant copies in more than one location.

Notice what those rules are doing. They are turning a camera from a device that makes pictures into a device that makes records with a provenance you can trace. That is the whole conversion.

2.1: Use fixed exposure settings for frames that will be measured, compared, or color-matched, and record the actual settings. If automatic exposure is used, preserve its metadata and evaluate whether changes between frames affect the analysis.

2.2Verify the camera clock against a known time reference before every job, record the reference you used, and record the offset if there is one.

What calibration means when it is not about color

Calibration deserves its own paragraph, because photographers hear the word and think of color. Calibration in the evidentiary sense means knowing what your instrument does to the thing it measures. A lens has a distortion signature. A sensor has a sensitivity floor and a saturation point. A scale bought from a forensic supplier has a manufacturing tolerance that may or may not match the specification printed on the package, a point that Chapter 5 takes up with the measured numbers. Every one of those is a property of your instrument that an opponent can look up, and every one is a property you should be able to state before the opponent does.

Compare what exists for the neighboring technology. If you bring a terrestrial laser scanner to a scene, ASTM International publishes test methods that let you say something defensible about that scanner's measured performance rather than repeating the manufacturer's brochure: ASTM E3125 for point-to-point distance measurement performance of spherical coordinate three-dimensional imaging systems in the medium range, and ASTM E2938 for relative-range measurement performance in the medium range. Run either one and you have a number that came from a published test method rather than from a sales page.

The scanner test methods named here do not provide a scene-photography verification protocol. Document how you evaluated the camera, lens, scale, and procedure for the intended analysis rather than treating the absence of a general standard as an exemption from verification.

Could someone else repeat your shoot and match it

Repeatability means that a specified procedure produces comparable results within a stated tolerance under comparable conditions. Fixed settings, recorded distances and angles, a tripod, and a scale help evaluate that property. Automatic settings and changes at the scene require documentation and assessment.

2.3Record, per frame, the lens and focal length, aperture, shutter, sensitivity setting, camera-to-subject distance, and the position and power of any light you brought.

Recording those settings supports review of the measurement procedure. Under Federal Rule of Evidence 702, as amended effective December 1, 2023, the proponent must show by a preponderance of the evidence that the expert's opinion reflects a reliable application of the principles and methods to the facts of the case. Documentation helps establish what was done; it does not by itself establish reliability.

Chapter 2 Checklist: The Instrument

Chapter 3What the Camera Sees and What the Eye Sees

The most dangerous sentence in a visibility case is not "I did not see him." It is "here is a photograph of what he could see."

A photograph alone does not establish what a witness could see. The image depends on the optical system, exposure, sensor, processing, display, and viewing room. Human visual performance depends on different mechanisms, including adaptation and viewing duration. A visibility analysis must address the differences relevant to the scene.

How long the eye takes to adapt to the dark

Start with adaptation, because it is where the argument is usually lost. The human visual system does not have one sensitivity. It has a sensitivity that moves, and it moves slowly. The cone system carries vision above about 0.03 candelas per square meter; below that the rod system takes over and provides scotopic, meaning night, vision. After 5 to 8 minutes in the dark, that second mechanism comes into play. Full dark adaptation, the point at which the rod threshold asymptotes to its minimum of about 10 to the minus 5 candelas per square meter, takes roughly forty minutes.

Light exposure can change rod sensitivity through rhodopsin bleaching. Applying laboratory threshold changes to a driver requires information about the intensity, duration, and location of the light exposure and the driver's adaptation state. A glance at a dashboard or an encounter with a headlamp does not by itself establish an orders-of-magnitude threshold change.

What else changes when the light goes away

Resolution and contrast move too. Photopically, meaning in daylight, peak contrast sensitivity reaches roughly one half of one percent contrast, and the acuity cutoff runs 50 to 60 cycles per degree. Scotopically, maximum contrast sensitivity is about eight percent and maximum resolution about 6 cycles per degree. Resolving power falls by roughly a factor of 10 and the contrast threshold worsens by roughly a factor of 16. The night driver is not a daylight driver in a dark room. He is a different instrument.

Then there is where he is looking. In daylight, acuity is foveal, and it degrades within 5 arcminutes of fixation, losing about a quarter of its value by 10 arcminutes off axis. At scotopic levels the picture inverts: maximum acuity sits at roughly 5 to 15 degrees of eccentricity, and peak rod density lies at 15 to 20 degrees. At night the best part of your vision is not where you are pointing your eyes. A photograph, which is uniformly sharp across the frame, represents neither condition.

Rod-mediated vision is achromatic, with peak sensitivity around 507 nanometers. A night scene may also contain light sufficient for cone-mediated color vision. Identify the lighting and adaptation conditions before concluding that a photograph contains color the observer could not perceive.

Human temporal integration differs with light level and visual task. A long camera exposure can accumulate detail not available during a brief view. Account for exposure duration, lighting modulation, frame rate, and playback before using video to represent an observer's experience. The cited quarter-second validation procedure should be described within its study conditions.

3.1Never offer a night photograph as a representation of what a witness could see without stating the adaptation state, the viewing duration, the display, and the calibration method you used to connect them.

Dynamic range in stops is not a sensor property

Practitioners quote "dynamic range in stops," a stop meaning a doubling or halving of light, as though it were a property of a sensor. It is not. It is a property of a sensor plus a choice about how much noise you are willing to call signal.

Bill Claff's published sensor analysis makes this concrete. For a Nikon D300 at the sensitivity setting marked ISO 100, engineering dynamic range, defined at the point where the signal to noise ratio crosses 1, computes to 12.37 stops. Photographic dynamic range for the same sensor at the same setting, defined at a signal to noise ratio of 20 and adjusted for the sensor's circle of confusion, computes to 9.00 stops. Same sensor. Same sensitivity. Same measured saturation point. A difference of 3.37 stops created entirely by the choice of noise criterion.

When an opponent cites dynamic range, ask which noise criterion produced the figure. If you use the number yourself, state the criterion in the same sentence.

Do not put a number on the eye's dynamic range

There is no authoritative published figure for the instantaneous dynamic range of the human eye. The commonly repeated span of fourteen orders of magnitude is not sourced, and the lower bound usually quoted is an order of magnitude below the rod absolute threshold the vision literature reports. Do not put that number in a report. You do not need it. The sourced facts about adaptation, threshold shift, contrast sensitivity, and eccentricity carry the argument by themselves.

3.2Do not state a figure for the dynamic range of the human eye. State the adaptation and threshold numbers instead, which are published and which prove the same point.

The display is part of the evidence chain

The reproduction chain matters as much as the capture. The central methodology paper in the nighttime visibility literature, on depicting night scenes by equivalent contrast, concedes in its own abstract that digital sensors and displays cannot reproduce the full dynamic range visible to human eyes. The foundational calibrated-print method from 1989 was, in its authors' own description, the production of a range of photographic prints from which the correct density level is selected by an observer at the site. Exposure and print density are discretionary choices, and the classical method admits it and builds an observer procedure to constrain them. The 1996 video work went further and required calibrating both recording and playback for the prevailing conditions.

If the validated method calibrates playback, an uncalibrated courtroom monitor falls outside that method. Evaluate the display before treating the exhibit as a validated visibility representation.

A lit courtroom display and the driver's nighttime view may involve different adaptation states. Determine whether the driver's relevant view was scotopic, mesopic, or photopic rather than assuming rod-mediated vision from the time of day alone.

The founder of the modern nighttime visibility literature wrote in 1987 that while such reconstructions can be helpful, they can also be very misleading. A later paper framed the evidentiary difficulty precisely: the determination of what would have been visible to the reasonably alert person must be made with proper consideration of both inter-person and intra-person variability. Neither of those is modeled by a photograph.

What you may say about a night photograph

A night photograph can document a scene under stated conditions. A visibility opinion requires additional support connecting those conditions and the imaging method to the observer and event. Under Federal Rule of Evidence 702, general reliability of a calibration method does not establish reliable application in the case. Under Rule 403, the court weighs the exhibit's probative value against the specified risks, including misleading the jury.

3.3Say what your photograph shows and stop there. It shows the scene under stated conditions through a stated instrument. It does not show what anyone saw.

Chapter 3 Checklist: Eye Versus Sensor

Chapter 4The Standards That Do Not Exist

There is no published American national standard for forensic scene photography. Not a weak one, not an outdated one, not one buried behind a paywall. There is none.

Distinguish published standards, draft standards, and guidance when describing the imaging method. Name the documents and explain how they apply rather than relying on a certificate alone.

The body most practitioners cite stopped publishing

The Scientific Working Group on Imaging Technology produced the foundational consensus documents of American forensic imaging, organized as numbered sections and compiled into a single volume of best practices for the forensic imaging practitioner. Its overview document, Section 1, sits at version 3.3 and is dated June 11, 2010. The working group ceased operations in the middle of the last decade, when its role was absorbed by the newer structure. Its documents are no longer maintained and are not updated. Its old web address no longer belongs to it and now serves unrelated commercial content, so do not send anyone there and do not print that address in a report.

This does not make the imaging working group worthless. It makes it legacy. Cite it for foundational principles, cite it with its date attached, and never let a citation to a 2010 document stand in for current practice.

Where current forensic imaging practice lives now

The live body is the Scientific Working Group on Digital Evidence. It is active, it publishes free versioned documents, it maintains dedicated photography, imaging, and video committees, and it has absorbed the imaging role the older group used to hold. Its photography committee alone maintains current guidance on low light crime scene photography, reflected ultraviolet and infrared imaging, technical aspects of digital cameras, photographic equipment recommendations, macro photography, evidence photography in a controlled setting, and image categories in forensic science. Its imaging committee maintains best practices for image authentication, for maintaining the integrity of imagery, for forensic image analysis, and for compression and file formats. Its video committee maintains the digital video and recorder acquisition documents.

That is where current practice lives. If you take one operational instruction from this chapter, take that one.

4.1Cite the digital evidence working group for current practice and the imaging working group only for principles, with its date attached.

The organization everyone names does not publish standards

The Organization of Scientific Area Committees for Forensic Science, administered by the National Institute of Standards and Technology, was created in 2014 to address a lack of discipline-specific forensic science standards. It runs a Forensic Science Standards Board for governance, a Standards Review Panel, Scientific Area Committees organized by discipline, subcommittees inside each, and cross-cutting resource task groups, with more than 800 volunteer members and affiliates across 19 forensic disciplines.

The organization does not publish standards. It writes drafts and pushes them to accredited standards developing organizations, principally the Academy Standards Board of the American Academy of Forensic Sciences, which is accredited by the American National Standards Institute, and ASTM International. Those bodies publish. The organization then decides whether to place the resulting published standard on its registry, which it describes as a repository of selected published and proposed standards containing minimum requirements, best practices, standard protocols, terminology, or other information. Inclusion on the registry signals that a standard is technically sound and that laboratories should consider adopting it.

Distinguish the drafting organization, publishing body, and registry. Name the actual document, status, and publisher rather than using an organization's name as a substitute for a standard designation. Registry inclusion supports consideration of a document but does not make one body the sole authority for all imaging practice.

4.2Never testify to compliance with a standard published by a body that does not publish standards. Name the publisher, the designation, and the year.

What is published, what is only a draft

Now the negative findings, stated plainly because plain statement is the credibility move. There is no published standard from the Academy Standards Board specifically on forensic photography or forensic imaging. Its Standard 220, on scene documentation, was open for public comment with a deadline of August 31, 2026. That is a draft. Track it. Do not cite it as published, and do not let anyone else cite it as published without correction.

ASTM International publishes terminology and performance documents relevant to this work. ASTM E2916 covers terminology for digital and multimedia evidence examination and sits on the registry in its American National Standards Institute approved form. ASTM E1732 covers terminology relating to forensic science. ASTM E2544 covers terminology for three-dimensional imaging systems, ASTM E2807 specifies a data exchange format, and ASTM E2938 and ASTM E3125 address measurement performance of medium-range three-dimensional imaging systems. Cite the applicable methods and the results of testing. Camera-based measurements also require evidence of performance appropriate to their intended use.

Federal Rule of Evidence 702 is what governs

So what governs? Federal Rule of Evidence 702 governs, and it is more demanding than a certificate would be. As amended effective December 1, 2023, the rule requires the proponent to demonstrate to the court by a preponderance of the evidence that the requirements are met, and subsection (d) requires that the expert's opinion reflect a reliable application of the principles and methods to the facts of the case.

The rule requires reliable methods and reliable application to the facts, along with its other requirements. Document applicable best practices, validation, and reproducibility. Certification and membership do not substitute for that showing, and adherence to guidance does not by itself establish admissibility.

The defensible posture is the same one that runs through every document I have named. Capture to examination quality. Preserve originals unaltered. Hash at acquisition. Process only working copies. Document every step well enough that a comparably trained person could repeat it and extract comparable information. That thread runs through the imaging working group's Section 11, the digital evidence working group's image processing guidelines, its compression and file format guidelines, and its integrity guidance. Four documents from two bodies across fifteen years, saying the same thing.

4.3When there is no standard, publish your own method in the report and make it the thing that is reproducible.

4.4Answer "what standard did you follow?" with the documents by name and the honest statement that no American national standard exists, then describe your method. Do not bluff and do not shrug.

Use the missing standard in both directions

The absence cuts both ways, and you should know how to use it in both directions. When your opponent claims you violated a standard, ask him to produce it. When your opponent claims that because no standard exists nothing was required, point him to the rule, which requires reliability regardless of whether anybody has written it into a designation. Same absence. Different verdict.

Chapter 4 Checklist: Standards and Authority

Chapter 5Gear That Earns Its Weight

Choose equipment for the intended documentation or measurement task.

Evaluate whether each purchase improves capture, verification, or preservation for the intended use. Aesthetic improvements alone do not establish evidentiary value.

Limits of phone capture

Phone images can include multi-frame processing, learned enhancement, and automatic color adjustments. The device, application, mode, and settings determine which processes operate. Evaluate those processes before relying on a phone image for measurement or comparison.

The clearest public demonstration remains the moon test. In March 2023 a tester downscaled a photograph of the moon to 170 by 170 pixels, blurred away the surface detail, displayed it across a room, and photographed it with a flagship phone. The phone returned an image with considerably more surface detail than the doctored source. Samsung's support documentation explains why: its scene optimizer recognizes the moon as an object, synthesizes more than ten images through a super resolution process, then applies a deep learning detail enhancement engine. The manufacturer stated publicly that it does not apply any image overlaying to the photo. That is narrow, true, and beside the point. A model trained on lunar imagery generated detail that was never in the light entering the lens.

5.1: Check whether a phone image uses multi-frame or learned processing. Before using it for measurement or color analysis, establish that the capture and processing support the proposed analysis.

Apple's deep fusion process and Google's night mode illustrate multi-frame phone processing. Google's night mode also applies learned automatic white balance. These processes require evaluation before using images for bruise coloration, paint transfer, corrosion, or burn-pattern analysis. Do not assume that every phone platform, mode, or file applies the same processing.

It gets worse for exhibits with people in them. Manufacturers now blend frames so everyone in a group looks their best, and at least one implementation merges facial expressions automatically at capture. The design goal is that the result feel true to the user's memory. Wrong standard.

Pixel area affects light collection when other exposure and sensor conditions are comparable. A 6.00 micrometer pixel has roughly 24 times the area of a 1.22 micrometer pixel and 100 times the area of a 0.6 micrometer pixel. Those ratios alone do not establish whole-image quality or whether a phone can produce a usable single exposure. Evaluate the complete capture system and its processing.

Where is a phone fine? Canvassing for cameras. Photographing a street sign so you remember the address. Anything where the image is a note and everyone knows it is a note.

Where to spend and where to stop

Every price below is a July 2026 snapshot, several promotional, and bodies are superseded every two to four years. Lenses, tripods, flashes, scales, and color targets change far more slowly. That is where your money should go.

An entry-level 24 megapixel APS-C body with suitable lenses, flash, and tripod can support a documented imaging procedure. Select the kit for the detail, scale, lighting, and preservation requirements of the assignment. Price and a written procedure do not guarantee admissibility.

Between $1,000 and $3,000 is the working expert's kit and this book's default recommendation. The defining feature is not the sensor. It is two memory card slots set to simultaneous backup, which a $1,999 full frame body provides and a $1,449 full frame body from the same manufacturer does not. Add a 90 to 105 millimeter macro lens, a normal prime lens, meaning one that does not zoom, a wide zoom, a radio-triggered flash plus one off-camera unit, a geared tripod head, scales, and a color target. Above $3,000 buys specialization: a 45 megapixel body at around $3,899, a twin macro flash, a tilt-shift lens, and a spare body.

Protect the capture before offload

Before offload, images may exist only on the camera's recording media. Simultaneous backup slots reduce dependence on one card, but they do not protect against every loss involving the camera. Verify capture and copy the files to separate storage as soon as practicable.

Select reliable, compatible cards and maintain separate verified copies. Neither price nor a second card eliminates the need to verify the files.

Which memory card your camera takes, and what each format buys

Cameras take one of two families, and the camera body decides for you.

The Secure Digital family, universally shortened to SD on the label, is the common one. The postage-stamp version is called microSD and turns up in action cameras and small drones. It is the same electronics in a smaller body, and it is easier to drop, easier to lose in gravel, and nearly impossible to handle with gloves on. Use the full-size card wherever the camera offers a choice.

Secure Digital cards are sorted by capacity, and the tier decides the file system, which decides whether your computer will read it without a fight. Standard cards stop at 2 gigabytes. The tier marked SDHC runs above 2 up to 32 gigabytes. The tier marked SDXC, which is what you will buy, runs above 32 gigabytes to 2 terabytes. A newer tier marked SDUC extends past that.

CFexpress is the faster family, built on the same signalling a computer uses to talk to its internal drive. It comes in Type A, which uses one data lane, and Type B, which uses two and is therefore roughly twice as quick. Type B in its current generation moves about 4 gigabytes per second. Your camera accepts one or the other and they are not interchangeable, so check the manual before you buy anything.

Read speed is the number on the front, write speed is the number that decides

The large number printed on the package is the read speed, which is how fast the card can hand data to a computer. It is the number you care about least in the field.

Sustained write performance affects how quickly a camera empties its buffer. Compare card and camera specifications and test the intended burst or video mode. The smaller write number matters, but buffer size, file size, bus support, and shooting rate also affect whether the camera stalls.

Buy on the video speed class instead, because it is the only figure on the card that is a guarantee rather than a maximum. A card marked V30 guarantees 30 megabytes per second of sustained write, V60 guarantees 60, and V90 guarantees 90. Note that V60 and V90 require the faster bus, and you can see whether a card has it: those cards carry a second row of contacts along the back edge. A fast card in a slow slot works, at the slow slot's speed.

5.2Buy on the guaranteed sustained write class, never on the read speed printed on the front.

Speed is not the same as reliability

A speed rating tells you how fast a card moves data on a good day. It tells you nothing about the four things that actually lose evidence.

The first is who made it and where you bought it. Counterfeit memory cards are a real and well-documented trade, and the usual forgery reports a large capacity to the camera while containing far less, so it writes happily and then silently discards frames. Buy from the manufacturer or an authorized dealer, keep the receipt, and never buy the cheapest listing of a premium brand.

The second is the controller inside, which is the part that spreads writes across the memory so no cell wears out early. This is where a card from a serious manufacturer and a nameless card of identical printed specification stop resembling each other, and it is not something you can inspect or test at the scene.

The third is endurance. Memory cells wear out with write cycles. A card that has been filled and reformatted every week for three years is not the card you take to the only inspection you will get.

Check each card's published temperature, moisture, shock, and static tolerances against the working conditions. Price or a professional label does not establish those limits.

5.3Buy from the manufacturer or an authorized dealer, keep the receipt, and never buy the cheapest listing of a premium brand.

Several medium cards beat one large one

A large card can hold an entire inspection, concentrating the risk if no separate copy exists. Card failure can make some or all of the files inaccessible. Choose capacity and backup arrangements together.

Two or three cards of moderate capacity spread the risk, and swapping between subjects gives you natural break points that match how the file is organized later. Label each one and log which card holds which sequence.

Handling that keeps the card an original

Format the card in the camera that will use it, never on a computer, because the camera writes the folder structure it expects. Do that at the start of a job, never in the field, and never on a card you have not already offloaded and verified.

When the shooting is done, treat the card as evidence rather than as a supply. Switch the write-protect tab if the format has one, and do not put it back in service until the files are copied, hashed, and verified in two places. Retire cards on a schedule instead of waiting for one to fail, and write the retirement date on the case.

5.4Format in the camera at the start of a job, never in the field, and never on a card you have not offloaded and verified.

Working distance decides which macro lens you buy

Working distance is the clear space between the front of the lens and the subject. Minimum focus distance is measured from the sensor plane and includes the camera and lens. Compare working distance at the required magnification, using manufacturer information where available and checking the actual setup.

Short working distance can obstruct lighting or access to the subject. A longer macro lens may provide more room for side lighting and separation from an injury or installed component. Check the intended setup rather than treating one focal-length range as a universal optimum.

5.5: Choose the macro lens for its working distance at the intended magnification, and verify that distance in the actual setup.

Verify the scale you will use

The National Institute of Standards and Technology reviewed commercially sold forensic photography scales against the design specification for the American Board of Forensic Odontology No. 2 scale, developed in 1988 by engineer William Hyzer and Dr. Thomas Krauss. That specification calls for circles of 19.75 millimeters internal and 23.00 millimeters external diameter, 80 millimeters center to center, with the legs perpendicular to within 2 arcminutes.

Across 20 rulers from 4 vendors, plus a survey of 50 rulers from 10 vendors, every vendor met the length requirement. Everything else failed. Circle external diameters ran from 19.176 to 20.396 millimeters against that 23.00 millimeter specification, so no vendor met it. Only one held the 80 millimeter spacing within 0.2 millimeters; five produced 84.9 to 85.2 millimeters. More than half fell outside the perpendicularity requirement, and factory quality control checked only the length scale.

The circles can help check alignment and support some rectification methods. Their suitability depends on verified geometry and the method used. Inspect and measure the actual scale before relying on those features.

5.6Verify your specific scale against a calibrated reference before you use it for anything you will testify to, document the verification, and retain the record.

Carry a color target that no standard requires

Carry a color reference target for color-critical work. Photograph it under the same light as the subject and in the same frame where practicable. The target supports checking and documenting color correction; it does not alone establish accurate color or replace evaluation of illumination, capture, processing, and display.

Buy the body last, and the scale first

Prioritize verified scales, color references, appropriate lenses, and redundant capture alongside the camera body. Choose the complete kit for the intended use.

Chapter 5 Checklist: The Kit

Part Two. The Craft

Chapter 6Exposure Without Guesswork

The camera does not measure light. It measures the light that bounced back off whatever you pointed it at, and those are two different quantities.

Three controls decide how much of that returning light reaches the sensor, and each one charges you for the privilege. Learn what each one costs and you will stop guessing.

Why the aperture numbers run backwards

The first is the aperture, the adjustable hole inside the lens. It is named by the f-number, which is the focal length divided by the diameter of the entrance pupil, the apparent opening you see when you look into the front of the lens. That definition explains why the scale looks strange on the dial: f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Every step multiplies the number by the square root of 2, which shrinks the diameter by about thirty percent and the area by half. So every step halves the light. An f/2 lens admits four times the light of an f/4 lens. Smaller number, bigger hole. Check the f-number sequence before setting exposure.

The shutter sells you time in doublings

The second control is the shutter speed, the length of time the sensor is exposed to the image: 1/1000 second, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 second. Each step doubles the time and doubles the light.

The sensitivity setting is not a measurement

The sensitivity setting marked ISO controls the relationship between exposure and recorded output. Raising it does not collect additional photons. The cited measurements by Emil Martinec show one professional body's read noise falling from 24 electrons at ISO 100 to 4.2 electrons at ISO 1600. That result describes that camera and noise component, not every benefit of changing ISO. Evaluate noise, highlight capacity, and exposure together.

6.1Shoot at or near the camera's base sensitivity whenever a tripod and thirty seconds are available to you.

One stop is a factor of two, everywhere

Because each step of each control is a factor of two, the three are interchangeable in a common currency called a stop. Open the aperture one stop and you can halve the exposure time, or halve the sensitivity, and the brightness is unchanged. What changes is everything else: depth of field, motion blur, and noise. Exposure value ties it together. It equals the base-two logarithm of the f-number squared divided by the exposure time in seconds, reckoned at ISO 100 by convention.

That gives you a field instrument needing no batteries. Sunny 16 says that on a sunny day, for a subject in direct sunlight, set f/16 and a shutter speed equal to the reciprocal of the sensitivity: at ISO 100, f/16 at 1/100 second. Run the arithmetic and that combination is exposure value 14.6, which rounds to 15, and 15 is precisely the published value for a typical scene in full or slightly hazy sunlight with distinct shadows. The rule and the table are the same statement. Open to f/11 for slight overcast, f/8 for overcast, f/5.6 for heavy overcast, f/4 for open shade or sunset, and add a stop for a backlit subject.

Use these exposure values as planning estimates: full sunlight, 15; heavy overcast or open shade in clear sun, 12; a bright street scene, 8; offices and work areas, 7 to 8; home interiors, 5 to 7; night vehicle traffic, 5. Meter and review the actual scene.

Suppose you want to hold f/5.6 and 1/125 second, a defensible handheld combination for a scene walk. In full sun you would need ISO 12, meaning you have three stops in hand at base sensitivity. At exposure value 12 you need ISO 96. On a bright street you need ISO 1,531. At night traffic levels you need ISO 12,250.

At exposure value 5, holding f/5.6 and 1/125 second requires a high sensitivity setting. Consider a tripod and longer exposure for a static subject, added light, a wider aperture if depth permits, or the noise cost of higher sensitivity.

The handholding rule was written for small prints

Handholding has its own arithmetic. The reciprocal rule says use a shutter speed numerically closest to the focal length, so a 50 millimeter lens wants 1/60 second and a 200 millimeter lens wants 1/200 second, applied to the 35 millimeter equivalent focal length on a smaller sensor. That rule was derived for six by four inch prints made from 35 millimeter film. Your file will be examined at full magnification on a courtroom monitor. Double the rule. Image stabilization buys back 2 to 5.5 stops, but it corrects camera shake only. It does nothing about a subject that is moving.

For the stated geometry, motion blur on the sensor can be estimated as subject speed times exposure time times magnification. Choose an acceptable blur limit for the measurement, calculate the exposure needed, and verify the captured feature. One-pixel blur is a possible criterion, not a universal requirement, and video measurability depends on the actual file and task.

6.2Write down the shutter speed the fastest thing in the frame requires before you choose the aperture you want.

What your meter assumes about the world

Your camera's meter reads reflected light, and it is calibrated on the assumption that the world averages out to a middle gray reflecting about eighteen percent of what falls on it. The standard output sensitivity method inside ISO 12232 is defined against exactly that eighteen percent gray. Scenes at issue in litigation are not eighteen percent gray. Snow, a white ceiling, a chrome guard rail, and a stainless housing all read brighter than the assumption, and the meter underexposes, which is how you come home with gray snow. Soot, black asphalt, a dark engine bay, and a matte black firearm read darker, and the meter overexposes, which is how you lose the surface detail you drove four hours to record. The same deception runs your flash: automatic flash units shut off too soon when they see reflected light from tile, white walls, or chrome, and the frame comes out dark.

Bracketing is a method, not a hedge

Bracket evidence close-ups when the useful exposure is uncertain. Capture the metered exposure and frames one and two stops below and above it. Retain the set and explain the basis for selecting or combining frames; a bracket does not by itself establish a correct rendering.

6.3Bracket every evidence close-up at plus and minus one and two stops, and keep every frame, including the ones you would never show.

Keep every frame is the part people skip. Merge a bracketed set into a single high dynamic range image and you have performed image enhancement as the Scientific Working Group on Digital Evidence defines it in its Image Processing Guidelines, document 15-M-002. The working group's foundational rule applies: the original image is preserved and processing is performed on a working copy, and the steps must be documented well enough that a comparably trained person can repeat them and extract comparable information. "Combined in Photoshop" does not satisfy that.

6.4: Record aperture, shutter speed, and sensitivity in the photo log and preserve the corresponding metadata.

Be prepared to explain the exposure choices and compare the log with file metadata. State what depth, blur, and noise criteria the setup was intended to meet and whether the resulting frames met them.

Chapter 6 Checklist: Exposure

Chapter 7Focus, Depth, and the Sharpness You Will Be Asked About

Sharpness is not a property of a photograph. It is an agreement between the photograph, the size you print it, and the distance the viewer stands away.

That sentence is the whole chapter, and it is the reason competent opposing counsel asks about focus at all. Depth of field is the range of subject distances that render acceptably sharp in the final image. The word doing the work is "acceptably." The engineering criterion behind it is the circle of confusion, the diameter of the blur circle a point source is allowed to become before an ordinary viewer calls it unsharp. The industry convention sets it at the frame diagonal divided by 1500. ZEISS derives that number from the eye's resolving limit in its own published whitepaper and confirms it corresponds to the widely used 0.030 millimeter figure for the 35 millimeter format. Divide a 43 millimeter full-frame diagonal by 1500 and you get 0.029 millimeters. For the smaller sensor sizes, published practice runs about 0.018 to 0.019 millimeters for the common crop formats and 0.015 millimeters for Four Thirds. Be careful with the round number 0.020 that many field references use for crop sensors: it sits inside published practice, but it is not the result the diagonal rule gives, and an opposing expert who has read the same references will notice.

Check the viewing assumptions behind depth-of-field tables

Depth-of-field tables and lens scales depend on a chosen circle of confusion. Check that assumption against the intended display size, viewing distance, and analytical task. Enlarging a file can reveal softness not apparent in a small print. Specify the viewing conditions when describing an area as sharp.

Choose focus for the required scene depth

The governing equations are old and stable. The hyperfocal distance, the focus distance at which depth of field extends from half that distance out to infinity, is the focal length squared divided by the product of the f-number and the circle of confusion, plus the focal length. Focus a 50 millimeter lens at f/8 with a 0.030 millimeter criterion and the hyperfocal distance is 10.5 meters, so everything from 5.2 meters to infinity is acceptably sharp. On full frame, a 24 millimeter lens at f/11 has a hyperfocal distance of 1.77 meters, and a 35 millimeter lens at f/8 has one of 5.14 meters. Those two settings will cover most scene overview work: the 35 millimeter at f/8 focused at 10 meters is sharp from 3.39 meters to infinity.

7.1: For scene overviews, calculate whether hyperfocal focus serves the required near and far detail, then record the chosen distance.

Why depth of field collapses as you move in

Depth of field changes linearly with f-number and with the circle of confusion, but it changes with the square of subject distance and inversely with the square of focal length. A 35 millimeter lens at f/8 focused at 3 meters in a room gives you a sharp zone from 1.90 to 7.16 meters, about five and a quarter meters of working depth. A 105 millimeter lens at f/8 focused at 2 meters gives you 0.17 meters. And a 100 millimeter macro lens at f/16 photographing a fracture surface at life size gives you roughly 10 millimeters of depth of field. Ten millimeters. On a fractured bolt, on a chipped gear tooth, on a tool mark in a door frame, one plane is sharp and everything else is not, and no aperture you can select will change that.

At comparable magnification and aperture, depth of field can be similar across focal lengths under the relevant approximation. Check focus distance, pupil geometry, and the selected sharpness criterion before treating the relationship as exact.

7.2: At high magnification, calculate and check the depth of field. Consider focus stacking when a single frame cannot resolve the required depth.

You cannot buy your way out with a smaller aperture

You cannot solve this by closing the aperture further, because the other end of the tradeoff is diffraction. Light passing an aperture spreads, and a point source images as an Airy disk whose diameter is 2.44 times the wavelength times the f-number. At the middle of the visible spectrum, around 550 nanometers, the Airy disk is 7.52 micrometers across at f/5.6, 10.74 micrometers at f/8, 21.47 micrometers at f/16, and 29.52 micrometers at f/22. Compare those against the sharpness criterion you already accepted and the conventional advice falls out on its own: on full frame the Airy disk equals a 0.030 millimeter circle of confusion at about f/22, so the practical floor is f/16. On the common crop formats, taking the round 0.020 millimeter figure, it crosses at about f/15, so the floor is f/11. On Four Thirds it crosses at about f/11, so the floor is f/8. Pushing past those apertures buys you depth and pays for it in resolution, and past a point the trade is losing on both sides.

Aberrations run the other direction: they fall as you stop down while diffraction rises, and the crossing point is the lens's sharpest aperture. For modern lenses of six or seven elements that optimum usually lands around f/5.6 to f/8. For older four-element designs, f/11.

7.3Work at f/8 unless you have a stated reason to be somewhere else, and be able to state the reason.

Write the focus distance down at the scene

Record focus distance, aperture, and depth-of-field assumptions for measurement images. Those records support later review, while the images and available metadata provide additional evidence. State uncertainties rather than treating a missing log entry as automatic failure.

A focus stack is a composite, and you must say so

Focus stacking combines frames taken at different focus distances to extend apparent depth. Use it when a single frame cannot resolve the required depth and the subject and method permit a reliable composite. Under SWGDE Image Processing Guidelines, document processing and retain source frames. State the frame count, step size, and software, label the output as a composite, and examine merge artifacts.

How to prove the defect is not blur

Use stable support and a remote release to reduce camera movement. Confirm focus on the feature at full magnification and capture frames on either side of the chosen focus distance. Compare those frames with other views or direct examination. Persistence or disappearance across focus settings alone does not distinguish a specimen feature from an optical artifact.

7.4: Photograph the surface at focus settings on either side of the feature to help evaluate blur and focus artifacts.

Chapter 7 Checklist: Focus and Depth

Chapter 8The Lens Is an Argument

A lens is a projection model with a price tag attached. Choose one and you have chosen where you must stand, and where you stand is the argument.

How much width you cover from where you stand

The angle of view of a rectilinear lens focused at infinity is twice the arctangent of the sensor dimension divided by twice the focal length. On a full-frame sensor of 36 by 24 millimeters, a 24 millimeter lens sees 73.7 degrees horizontally, a 35 millimeter sees 54.4 degrees, a 50 millimeter sees 39.6 degrees, an 85 millimeter sees 23.9 degrees, and a 200 millimeter sees 10.3 degrees. Translate that into the number you need at a scene, which is how much width you cover from where you stand. At 20 meters, a 35 millimeter lens covers 20.6 meters of width, a 50 millimeter covers 14.4 meters, and a 105 millimeter covers 6.9 meters. Decide the lens before you take a step, not after.

Sensor size sets the scale. Full frame is about 36 by 24 millimeters, diagonal 43.3 millimeters. The common crop formats measure 23.6 by 15.6 or 22.3 by 14.9 millimeters, crop factors of about 1.52 and 1.61, and Four Thirds is 17.3 by 13.0 millimeters, a crop factor of exactly 2. Crop factor is the ratio of the full-frame diagonal to yours, so a 50 millimeter lens on a 1.6 crop camera body frames like an 80 millimeter lens on full frame. It is still a 50 millimeter lens, and every calculation in this book uses the real number. Be careful with sensors specified in inches: those fractions come from 1950s video camera tubes, where the number described the outside diameter of the glass envelope, and the real sensor is roughly a third smaller than the fraction implies.

Fifty millimeters is not what the eye sees

You will be asked whether your photograph shows the scene as a person would have seen it, and the honest answer requires separating two claims that everyone else runs together. A "normal" lens is conventionally one whose focal length equals the frame diagonal, 43.3 millimeters on full frame, with anything from 40 to 58 millimeters also called normal. The famous 50 millimeter standard was chosen by Oskar Barnack when he built the Leica: a historical accident, not an optical derivation. And the justification for the diagonal rule is a viewing argument, not a vision argument. Such a lens covers about 53 degrees diagonally, the angle subtended by a print viewed at a distance equal to its own diagonal.

Human field of view and acuity distribution differ from a photograph's frame and resolution. A normal lens can support a defined viewing geometry when print size and viewing distance are controlled. It does not reproduce the observer's visual experience. Describe camera position, field of view, and presentation conditions rather than saying a focal length is what the eye sees.

8.1For any image offered to show what a person could see, use 40 to 50 millimeters equivalent from the measured eye position, and document the eye height and position, because the camera position is the substantive claim.

Perspective comes from distance, not from the lens

Linear perspective depends on viewpoint. For the same viewpoint and projection, changing focal length changes framing rather than relative perspective geometry. Moving to maintain framing changes the relative apparent sizes of near and distant objects. Explain those choices when spatial relationships matter.

The numbers make it undeniable. Take two identical objects separated by 5 meters in depth. Photograph them from 2 meters and the near one images three and a half times the size of the far one. From 20 meters, 1.25 to 1. From 100 meters with a long lens, 1.05 to 1: they look identical.

Evaluate whether viewpoint, framing, and presentation support the proposed use; geometry alone does not determine admissibility.

Changing viewpoint to maintain framing with different lenses changes apparent depth and relative feature size. Record camera position and focal length, and select views suited to the spatial question. A focal length above 135 millimeters does not automatically misrepresent a relationship, and a normal lens from the same position does not change that perspective.

8.2Use 90 to 105 millimeters for injury, component, and failure-surface work, and never wider than 24 millimeters equivalent for anything that shows spatial relationships.

Barrel, pincushion, and the kind that will not correct

Barrel distortion means magnification decreases with distance from the optical axis, so straight lines bow outward; it lives at the wide end. Pincushion means magnification increases with distance from the axis, so lines bow inward; it lives at the long end. Mustache distortion is a mixture, barrel near the center turning to pincushion at the edge, and because its radial coefficients change sign, a one-coefficient correction cannot fix it.

Percent distortion is the actual radial distance of an imaged point minus the paraxially predicted distance, divided by the predicted distance, times one hundred. Watch the sign convention, because it is not universal. Edmund Optics calls barrel negative and pincushion positive, and offers the tolerance that 2 to 3 percent goes unnoticed when no measurement algorithm is running. DXOMARK uses the opposite convention and calls 1 percent absolute value the usual acceptable limit. Cite a figure without stating whose convention it follows and a competent cross-examiner will invert your sign for you.

LensTip's cited uncorrected measurements illustrate variation among specific lenses and zoom settings, including 0.12 percent barrel distortion for a 55 millimeter prime and 6.12 percent for a 15 millimeter lens. Those results do not establish that all normal primes are nearly distortion-free or that a distortion percentage translates into a fixed scene-distance error. Calibrate the actual measurement setup.

8.3Record the exact focal length used for every frame, because a zoom lens is a different lens at every setting, and the metadata will be asked for.

Distortion correction moves the focal length without telling you

LensTip measured that same 15 millimeter lens by star-field astrometry, fitting 137 stars in the corrected frame and 126 in the uncorrected one. Uncorrected, the lens showed 6.12 percent barrel distortion, a measured horizontal angle of view of 93.53 degrees, and an equivalent rectilinear focal length of 13.3 millimeters. With the camera's distortion correction turned on, the same lens showed 0.09 percent distortion, 89.56 degrees, and an equivalent focal length of 14.3 millimeters. The manufacturer's published angle of view is 86.9 degrees, which matches neither one.

In the cited test, correction changed field of view by about 4 degrees and equivalent rectilinear focal length by about 1 millimeter. Fixing focal length at the nominal value without calibration can introduce reconstruction error. Assess the camera model and solution rather than translating a focal-length difference directly into a universal reconstruction error.

The photogrammetry standard is silent where the risk is

The standards do not save you here. The Scientific Working Group on Digital Evidence treats geometric correction as image restoration in its Image Processing Guidelines, document 15-M-002, and requires that the original be preserved and that steps be documented well enough for a comparably trained person to reproduce them. But the working group's own Best Practices for the Forensic Use of Photogrammetry, version 1.2, does not address camera or lens calibration, does not address distortion correction, and does not say whether corrected imagery is acceptable input. It is silent exactly where the technical risk lives. Say so plainly in your report. A gap named by you is a gap that cannot be sprung on you.

8.4For any image that will be measured, calibrate that specific body and lens at that specific focal length and focus distance, and never rely on the number printed on the barrel.

Calibration recovers two focal length terms and two principal point coordinates in pixels, plus three radial and two tangential coefficients modeling the misalignment of the elements. Shoot raw, archive the uncorrected original, calibrate, and document the correction status of the file you analyzed. If the work is metrology, leave the zoom in the bag. Two rules sit behind all of it. Federal Rule of Evidence 901 requires evidence sufficient to support a finding that the item is what you say it is, and illustration (b)(9) lets you satisfy that by describing a process or system and showing that it produces an accurate result. Federal Rule of Evidence 403 lets the court exclude relevant evidence when its probative value is substantially outweighed by the danger of misleading the jury. A photograph that exaggerates or compresses depth is not a lie. It is a candidate for that second rule.

Chapter 8 Checklist: The Lens

Chapter 9Light You Find and Light You Bring

Lighting failures can involve direction, intensity, glare, spectral content, or changes during capture. Evaluate lighting against the feature being documented.

When the light you find stops being enough

SWGDE's Guidelines for Low Light Crime Scene Photography address available-light capture with long exposures, stable support, and exposure control. Ambient light can document context and reveal texture when its direction and contrast are suitable. Check the actual illumination before adding light.

Directional lighting can reveal relief through shadows and changes in luminance. Perspective, occlusion, and surface shading can also convey depth. Choose lighting that reveals the feature without overstating its dimensions.

The flash on top of the camera erases shadow

Near-axis flash can hide shadows behind raised features and reduce visible texture. Compare axial and oblique lighting when relief matters. Similar-looking lines may have different physical causes, so do not identify a striation or an ink line from one lighting geometry alone.

Specular reflection can obscure detail or clip channels, depending on geometry and exposure. Compare off-axis lighting, diffusion, tenting, or cross-polarization as appropriate. Record the method and check results. In injury documentation, disable appearance-changing corrections and record any pre-flash used.

9.1Take the flash off the camera for every evidence photograph, and use the built-in flash for nothing but orientation snapshots.

Flash falloff also limits coverage. For a point-source model, illumination falls as the inverse square of distance: doubling the distance reduces illumination to one quarter, or two stops. Under the same source and incidence conditions, points at 1.5 and 6 meters differ in illumination by a factor of 16, or four stops. Moving the source changes that ratio. Source size, beam shape, additional lights, and exposure choices also affect the recorded result; evaluate the actual setup.

Guide numbers turn that physics into a setting: the guide number equals the f-number times the distance. It means nothing without a stated sensitivity, normally ISO 100, the sensitivity setting marked on every camera, and nothing without a stated zoom head position. Manufacturers quote it at the longest zoom, which inflates it: Nikon publishes one professional flash at 34.5 meters with the head at 35 millimeters and 55 meters at 200 millimeters, which is 1.35 stops of apparent extra reach created entirely by narrowing the beam. Cutting manual power one stop multiplies the guide number by 0.707; doubling the sensitivity multiplies it by 1.41.

9.2Use manual flash power for every image that will be examined, compared, or measured, and reserve automatic metering for orientation frames where the exposure is not the evidence.

Manual flash settings help maintain and document a consistent setup. Automatic metering can vary output between frames, so record the mode and evaluate its effect. A power setting alone does not establish repeatability without position, distance, modifiers, and exposure information.

A softbox is not soft, closeness is soft

Shadow-edge softness depends strongly on the source's angular extent at the subject. Moving a given softbox closer increases that extent, but source dimensions and illumination geometry also matter. Evaluate the actual shadow rather than treating distance alone as softness.

The standard names a criterion, not an angle

Oblique lighting can improve contrast in impressions, striations, abrasions, and dents. SWGDE's Lighting Techniques document specifies a low enough height and angle to cast a shadow into the subject, adjusted for appropriate contrast, rather than a universal degree setting. Select and record the angle for the actual surface.

What you can give the court are documented working values. Steven Staggs, in the standard practitioner text on crime scene photography, specifies impression photography with an electronic flash at 25 degrees and again at 45 degrees, from each of three directions, six frames minimum. The working group's angle for direct, non-oblique lighting is 45 degrees. Shallow relief such as dust impressions and indented writing calls for a lower, near-grazing angle.

For an ideal feature of height h and the stated planar geometry, shadow length equals h divided by the tangent of the light angle. Lower angles lengthen the shadow and can improve visibility of small relief. Whether the camera resolves the feature or shadow depends on magnification, focus, sampling, and contrast.

Shadow length is not a measurement of depth. Oblique light exaggerates relief by design, and the lower the angle, the greater the exaggeration. Record the angle for every frame, and do not let a jury read shadow length as depth.

9.3Record the flash angle from the surface plane, the flash-to-subject distance, the compass or clock direction, and the manual power fraction for every oblique frame.

Light every impression from all four cardinal points

SWGDE's Guidelines for Digital Imaging of Footwear and Tire Impressions, document 17-P-003 version 2.0, call for ambient-light photographs and oblique lighting from various angles, including the four cardinal points. Directional lighting can conceal relief aligned with the light. Multiple directions reduce that risk; visibility also depends on shape, reflectance, and surrounding illumination.

The rest of the setup is prescribed and short. Camera on a tripod with the sensor plane parallel to the impression, because parallel is what keeps the geometry measurable. A scale on the same plane, with focus on the bottom of the impression. Fill the frame. Use a lossless format at the camera's highest resolution and a fixed focal length lens of 50 millimeters or longer. Set the aperture about two stops down from the widest opening. Subdue the ambient light and verify it with one flash-disabled frame, which should come out black.

When no flash is big enough, paint the scene

When one flash cannot illuminate a large dark scene adequately, painting with light can combine several flash exposures in one open-shutter frame. SWGDE's starting point uses bulb, f/8, ISO 400, stable support, manual settings, and an opaque cover between flashes. Keep lights and the operator out of the recorded exposure and review for unwanted illumination.

For a fixed flash geometry, estimate repeated-flash exposure from the guide number, aperture, distance, and sensitivity, then bracket and verify. Record flash positions and pop counts, cover the lens between exposures, and inspect for operator or stray-light artifacts. Counting helps documentation but does not alone establish repeatability.

9.4: Bracket painted-light frames from a locked camera position, record changes in pop count and angle, and review on site for missing detail and artifacts.

Chapter 9 Checklist: Light

Chapter 10Beyond Visible Light

Visible light is a narrow band that happens to match your eyes. The silicon behind your lens was never that fussy, and the manufacturer had to install filters to make it behave.

That is the engine of this chapter. A bare digital sensor responds far outside the roughly 400 to 700 nanometer band the eye uses, and every ordinary camera ships with internal blocking glass to discard the parts nobody asked for. Remove that glass, or buy a camera built without it, and you can photograph two things that were present at your scene the whole time and invisible the whole time: reflected ultraviolet radiation and reflected near infrared radiation. Both are ordinary light. Both obey the same lens, the same tripod, and the same exposure arithmetic you already know. Neither requires you to believe anything mystical.

What ultraviolet shows after white light gives up

Start with ultraviolet, because it is the technique most likely to get you in trouble. The Scientific Working Group on Digital Evidence publishes Guidelines for the Use of Reflected Ultraviolet Radiation in Forensic Photography, document 19-P-001, and it places the ultraviolet band at roughly 10 to 400 nanometers, with two emission wavelengths that matter in the field: 254 nanometers and 365 nanometers. The applications are real and documented. Healing injuries, diminished bruising, latent impressions, surface disturbances on flooring, and text on thermal receipts all photograph under reflected ultraviolet after they have gone invisible under white light.

Shortwave ultraviolet can destroy the evidence on the item

The working group's own limitations section states that exposure to ultraviolet may denature deoxyribonucleic acid, and it puts a threshold on it: wavelengths below 280 nanometers denature deoxyribonucleic acid rapidly during exposure. Read that as an engineer, not as a lawyer. Shortwave ultraviolet photography of an item can destroy the biological evidence sitting on that item. Not degrade. Destroy.

10.1Decide before you open the case whether the item gets swabbed first or imaged first, write that decision in the log with a time, and tell every person on site which order you are in.

Coordinate ultraviolet imaging and biological sampling before either begins. Swabbing may disturb a feature, and ultraviolet exposure may damage biological material. Wavelength alone does not establish safety; consider exposure and laboratory requirements. Record the agreed sequence and authorization rather than treating another person's approval as a substitute for technical assessment.

A filter that leaks is not making an ultraviolet photograph

The second ultraviolet trap is the filter, and here the working group has done the field an enormous favor by publishing measured numbers. An ultraviolet transmitting filter is supposed to pass the ultraviolet band and block everything else, but several of the classic filters leak badly in the near infrared. The Kodak 18A passes 300 to 400 nanometers and leaks 14 percent at 746 nanometers. The B&W 403 leaks 17 percent at the same wavelength. The Schott UG-1 leaks 9 percent. Against those, the Baader U-Venus passes the same 300 to 400 nanometer band and leaks 0.15 percent at 737 nanometers, and the Kolari Vision ultraviolet filter, passing 320 to 400 nanometers, leaks 0.025 percent.

Near-infrared leakage can contribute to an intended ultraviolet image. Its effect depends on illumination, filter transmission, subject, and sensor response. Assess those conditions before attributing a feature specifically to ultraviolet reflectance.

10.2Name the filter make, model, pass band, and published leakage figure in the report, and buy the filter with the smallest leak you can afford.

Ultraviolet focuses at a different point than visible light, and each lens has a different focus shift, so autofocus achieved in visible light is not focus in ultraviolet. Most ordinary glass absorbs ultraviolet below about 350 nanometers, which is why dedicated work uses lenses with quartz or fluorite elements. And the exposure limits are not decorative: the International Commission on Non-Ionizing Radiation Protection sets the effective radiant exposure limit for unprotected eye and skin at 30 joules per square meter over any 8 hour period, with the hazard weighting peaking at 270 nanometers, and an unweighted limit of 10,000 joules per square meter for the 315 to 400 nanometer band. Wear ultraviolet blocking eyewear. Ordinary sunglasses are not that.

Near infrared separates materials the eye reads as identical

Infrared is the gentler sibling. The working group's companion document, 19-P-002, identifies near infrared from 700 to 900 nanometers as the practical forensic range and notes that a silicon sensor may reach only about 1,100 nanometers regardless of what you put in front of it. Infrared also focuses at a different point than visible light, which is why the guidance directs you to focus using live view through the installed filter rather than trusting the visible-light focus. Infrared penetrates the upper layers of skin, which makes it useful for tattoo and bruise documentation, and it discriminates materials that look identical to the eye, which makes it useful for blood on dark fabric, gunshot residue on clothing, ink comparison, and questioned documents. The guidance is blunt about the output: infrared images carry no color data and should be converted to black and white after capture. Do not hand a jury a false-color infrared frame and let them read hue as meaning.

A thermal image is not a temperature measurement

A thermal camera measures radiation and converts the signal to apparent temperature using calibration and assumptions about emissivity and reflected background radiation. A representative Teledyne FLIR E8 Pro has a 320 by 240 detector and published accuracy of plus or minus 2 degrees Celsius or 2 percent of reading under specified conditions. Evaluate instrument limits, emissivity, reflections, distance, and target coverage before reporting temperature. Bare reflective metal requires particular care.

10.3Never call a thermal image an infrared photograph, and never state a temperature from one without stating the assumed emissivity in the same sentence.

Thermal work also carries a constitutional footnote worth knowing even in civil practice. In Kyllo v. United States, 533 U.S. 27 (2001), the Supreme Court held that where the government uses a device that is not in general public use to explore details of a private home that would previously have been unknowable without physical intrusion, the surveillance is a search and is presumptively unreasonable without a warrant. The technology has become far more common since 2001, but the instinct to point a thermal camera at somebody's house from the street should still trigger a phone call to counsel.

How fluorescence works, and what you must record

Alternate light sources sit between these techniques. A narrowband source excites fluorescence, the subject re-emits at a longer wavelength, and a barrier filter on the camera and on your goggles blocks the excitation so you can see the faint re-emission. Yellow pairs with blue excitation, orange with blue-green, red with green. A commercial unit such as the Foster and Freeman Crime-lite 82S PRO offers bands from 350 to 380 nanometers through 800 to 900 nanometers, and the working group imposes exactly one documentation duty in its low-light guidance: record the wavelength used and the filter combinations used.

Be honest about what fluorescence proves. A randomized controlled trial by Scafide and colleagues, published in the Journal of Forensic Sciences in 2020 across 157 subjects balanced over six skin color categories, found 415 nanometer excitation with a yellow filter improved bruise detection over white light with an odds ratio of 5.34, and 450 nanometers with yellow gave 4.08. The authors framed their own result carefully: alternate light enhances concurrent physical assessment in the presence of a known history of injury. The counterweight is Lombardi and colleagues in 2015, who measured specificity of roughly 51.6 percent on day one against 71.0 percent for white light and concluded that fluorescence under an alternate light source is not sufficient to accurately or responsibly diagnose subclinical bruising. Roughly half of uninjured control forearms fluoresced in a way readers called a bruise.

10.4Treat fluorescence as presumptive, never confirmatory, and shoot a white-light control frame of the identical field before you shoot the fluorescence frame.

Chapter 10 Checklist: Beyond Visible Light

Chapter 11Color You Can Defend

Color-critical photographs require control of capture, processing, and display.

What your camera does to color before you see it

In a Bayer color filter array, each photosite samples one filtered band, and demosaicing estimates the other channels. White balance adjusts channel gains but cannot recover reflectance information the illuminant did not reveal. The same subject can render differently under different lights. Evaluate that difference rather than treating white balance as complete color correction.

Color fidelity depends on capture and processing. A reference target helps evaluate the result but cannot replace suitable illumination or a documented display workflow.

A gray card does two jobs, not one

A gray card can support white balance and exposure checks, but those uses require known reflectance and a suitable capture procedure. Apparent grayness alone does not establish spectral neutrality, and raw channel equality depends on illumination and sensor response. Use characterized references and document the processing.

What an opposing expert will ask about your chart

For serious work, use a color reference chart. The ColorChecker Classic, described in a 1976 paper by McCamy, Marcus, and Davidson, carries 24 patches in a four by six grid with six neutrals across the bottom row, and it lets an opposing expert re-derive your color correction from your own image rather than take your word for it. Two facts about that chart will be used against you if you do not know them. First, the colorants were reformulated in November 2014, which moved patch values by an average color difference of 0.85 and as much as 1.95, and the manufacturer publishes separate reference data for pre-2014 and post-2014 charts. Your report must state which set you applied. Second, no colorant is absolutely resistant to fading, and the manufacturer's maintenance guidance says to store the chart in its black cover and replace it every two years.

11.1Photograph the chart in the same light, at the same distance, and in the same plane as the subject, with exposure within a quarter stop of correct, a stop meaning a doubling or halving of light, and the light striking it at 20 to 45 degrees.

11.2Shoot every color-critical subject twice, once with the reference in frame and once without, and keep both.

That two-frame habit has real precedent. The American Board of Forensic Odontology's reference manual requires photographs both without and with a properly placed and labeled reference scale, on the same plane as the injury. The logic transfers directly: the frame with the reference makes your correction auditable, and the frame without answers the objection that the reference obscured the scene. Be candid, though, about where the authority runs out. No forensic standard requires a color reference inside the evidentiary frame. Several list one as optional equipment; one describes it purely as a white balance tool. The practice I am recommending is ahead of the published guidance, not derived from it, and you defend it by analogy to the odontology board's scale rule and to the reproducibility principle that governs image processing generally.

The PRESSURE 2 photographic validation sub-study protocol, published in Trials in 2017, specified a gray scale for white balance and a calibrated monitor for review. That protocol illustrates controls for its tissue-color endpoint. Select and justify controls appropriate to the color question in the case.

Color you captured correctly can still be shown wrong

Which brings in the display, because color you captured correctly can still be shown wrong. The International Organization for Standardization's proofing display standard, ISO 12646:2015, requires room illumination below 32 lux anywhere between monitor and observer, at roughly 5000 Kelvin, with a color rendering index above 90. The Federal Agencies Digital Guidelines Initiative sets its review stations to a gamma of 2.2 in a neutral matte gray room, with calibration verified weekly. None of that describes a courtroom. Say so in your report before opposing counsel says it for you.

A light that is not a blackbody radiator has no true color temperature, only a correlated one, and as Ohno's paper for the National Institute of Standards and Technology puts it, chromaticity is two-dimensional while correlated color temperature reports only one dimension. The missing dimension is Duv, the perpendicular distance from the light's chromaticity point to the Planckian locus. Two lights sharing a stated color temperature can sit on opposite sides of that curve and look plainly different.

11.3Capture raw so the white balance stays a reversible metadata parameter, choose the working space in processing, and deliver sRGB with the profile embedded for court display.

Dating a bruise from color has no scientific basis

Dating a bruise from its color in a photograph has no scientific basis. That is not my characterization. It is the conclusion of the systematic review by Maguire, Mann, Sibert, and Kemp in Archives of Disease in Childhood in 2005, which screened 167 studies, found only three that met inclusion criteria, and concluded that a bruise cannot accurately be aged from clinical assessment in vivo or on a photograph, that the practice of estimating the age of a bruise from its color has no scientific basis, and that it should be avoided. The 2013 update did not rehabilitate it.

The underlying data is worse than the summary suggests, and it fails at two separate layers.

The first layer is the photograph itself. Munang, Leonard, and Mok had three observers describe the color of 58 bruises on 44 children, both in person and from photographs. Complete agreement between two observers on the color description ran twenty-seven percent in person and twenty-four percent from photographs. Clinicians could not agree on what color the bruise was, and agreement got worse on photographs than in the room. Every dating opinion built on a photograph is stacked on top of that.

The second layer is the inference from color to age. Bariciak and colleagues, in Pediatrics in 2003, showed history-blinded examiners 50 children with accidental bruises of known age. Accuracy within 24 hours was 47.6 percent for emergency pediatricians, 29.4 percent for other physicians, and 36.8 percent for trainees, with individual accuracy ranging from zero to 100 percent. Interobserver reliability came out at a kappa of negative 0.03. Zero is chance. Negative means the observers agreed less often than random guessing predicts. The examiners relied primarily on color, and color showed no significant correlation with accuracy. Pilling and colleagues in 2010 ran the same test on 15 forensic experts using 132 images of 25 bruises of exactly known age from zero to 209 hours, and the median difference between estimated and actual age was 26.0 hours.

Langlois and Gresham reported in their 1991 study of 369 bruises across 89 subjects that a bruise with yellow color could be concluded to be more than 18 hours old. That finding does not establish ages for red, purple, or non-yellow bruises. The subjects were under 65. Thavarajah, Vanezis, and Perrett's 2012 study of 18 dark-skinned individuals found limitations in detecting yellowing because of pigmentation. Do not convert these findings into a universal photographic dating rule.

11.4: Do not date a bruise from photographic color alone. If discussing a study's color finding, state its population, method, and limits.

Attack the measurement and the inference separately

Evaluate the color measurement and the age inference separately. Identify the actual basis and evidence for each before assessing the resulting opinion.

Ask about illumination, reference targets, file format and processing, and monitor calibration. Determine the actual chroma-subsampling scheme before quantifying color-data reduction. Assess whether the remaining color information supports the proposed inference.

Ask which study supports the color-to-age inference and whether its subjects and methods apply. Compare its findings with reliability limitations in other studies, including Bariciak's. Explain the resulting limits rather than assuming a line of questioning determines the outcome.

Chapter 11 Checklist: Color You Can Defend

Chapter 12Scale, Measurement, and the Parallel Plane

A scale is not a ruler in a picture. It is a claim that the picture can be measured, and every claim invites a question.

For direct planar measurements, place a verified reference in the evidence plane, align the camera, and document the method. Otherwise, assess whether a validated geometric reconstruction can support measurement and quantify the uncertainty.

The L-shaped forensic scale does three separate jobs

The ABFO No. 2 scale described by Hyzer and Krauss combines graduated legs, tonal patches, and circles for geometric checks. Verify the dimensions used in measurement or rectification. Tonal bars can assist exposure assessment but cannot guarantee recovery from clipped image data.

The board's published specification carries four numbers. Length accuracy of plus or minus 0.1 millimeter or 1 percent for the major centimeter graduations. Circle diameters of 19.75 millimeters internal and 23.00 millimeters external. Circle center spacing within 0.25 percent of a nominal 80 millimeters. And legs mutually perpendicular within 2 minutes of arc.

What happened when someone measured the scales themselves

The National Institute of Standards and Technology published a Dimensional Review of Scales for Forensic Photography in which it measured commercially sold scales against a system with roughly 0.001 millimeter uncertainty, nearly two orders of magnitude tighter than the tolerances being checked.

The linear graduations passed. Every vendor stayed well within the allowed error across the range tested, most within 0.1 millimeter at the 5 centimeter graduation.

The circles did not. None of the vendors achieved the specified 23.00 millimeter external diameter, with actual measurements running from approximately 19.176 to 20.396 millimeters, a shortfall of 2.6 to 3.8 millimeters on a 23 millimeter specification. Only one vendor came close on internal diameter. Only one met the spacing tolerance. More than half the rulers tested failed the perpendicularity specification. The institute's site visits found that manufacturers typically checked only the length graduations, often by visually comparing plastic scales against certified steel rulers, and applied their own tolerances rather than the published specification.

Understand what that means before you shrug at it. The circles are the feature relied on for perspective rectification. A circle in the subject plane images as an ellipse when the sensor is tilted, and the ratio of the ellipse's minor axis to its major axis is what tells you the tilt angle. That relation is geometry you can derive at the kitchen table, not a published forensic standard, so present it as derivation. Three circles at known separation, rather than one, are what make a full projective correction of the whole frame tractable instead of a single-axis fudge. If the circles are not the diameter they are supposed to be, and not the distance apart they are supposed to be, then the correction derived from them carries an error nobody has quantified, and the rectified image is offered to a jury as though it were geometry.

12.1Verify your own scale against a traceable standard, record the measured values, and be prepared to say on the stand whether the circles on that particular scale were checked.

Hold the sensor plane parallel to the subject

The better answer is to avoid needing the correction. The parallel plane rule is stated in every relevant guidance document. The Organization of Scientific Area Committees for Forensic Science, in its guide for crime scene photography, directs you to place the camera lens perpendicular to the subject. The legacy Scientific Working Group on Imaging Technology told you to mount the camera on a tripod with the focal plane parallel to the impression. The tread evidence working group said film plane parallel to impression. Different bodies, different decades, one instruction.

The arithmetic behind it is simple enough to put in a report. A subject plane tilted by an angle from the sensor plane is foreshortened along the tilt direction by the cosine of that angle. At 5 degrees you under-read by 0.38 percent. At 10 degrees, about 1.5 percent. At 20 degrees, 6.0 percent. At 30 degrees, 13.4 percent. At 45 degrees, 29.3 percent. Show the cosine when you present those numbers, because they are derived geometry rather than a published table, and derived geometry survives cross-examination when you show the derivation.

Tilt can change apparent shape and scale. Under perspective, magnification also varies across the image. Assess those effects with the actual projection and reference geometry before drawing dimensional or aspect-ratio conclusions; an uncorrected tilt does not automatically corrupt every possible opinion.

12.2Use a tripod and the camera's dual-axis level for every measurement image, and photograph the level indication if the geometry will be contested.

The scale must sit at the depth you measure

Placement is the other half of the geometry. The guidance is emphatic and consistent: the entire scale shall be on the same plane as the subject. For macro work, the scale goes at the edge of the frame and fills no more of it than necessary. For a three-dimensional impression, the scale sits at the depth of the feature you intend to measure, and the tread evidence guidance goes further and tells you to focus on the bottom of the impression rather than on the scale.

The reason is worth stating plainly to any jury, because it is intuitive once said. A scale calibrates the image only at its own distance from the lens. In a perspective projection, magnification varies as one over distance. A scale sitting 10 percent closer to the lens than the evidence is imaged 10 percent larger than the evidence, and every measurement you derive inherits that ratio error directly, with no warning in the picture.

When the scale belongs in the frame at all

The crime scene photography guide says photographs should be captured with a scale any time relative size is in question, and that if a scale is used, the photographer shall be certain a photograph is first captured without the scale. Note the mandatory verb and note the ordering. The scale is an object you introduced into the scene. The unscaled frame proves it is not concealing anything and preserves the scene in its found condition.

12.3Shoot the no-scale frame first, then the scale frame, from the same position without moving the camera.

There is a widespread belief that a 6 inch or 15 centimeter rule is the standard forensic scale length. I could not find any standard that designates one. Vendors sell many lengths. Choose a scale roughly the size of the item, say why you chose it, and do not claim a standard that does not exist.

Why your close-up work comes out soft

At close range, evaluate effective aperture and depth of field for the actual lens. The marked aperture alone may not describe diffraction at the working magnification. Check focus, motion, and processing as well as diffraction when a macro image is soft. A documented focus stack is one option when a single frame cannot resolve the required depth.

12.4If you focus stack, preserve every source frame unaltered, document the steps to a reproducibility standard, and disclose in the report that the exhibit is a composite.

A focus-stacked image is a computational composite. Preserve source frames, process working copies, and document the steps so a comparably trained person can reproduce the process. Identify software, settings, and source sequence, label the composite, and evaluate artifacts.

Chapter 12 Checklist: Scale and Geometry

Chapter 13Raw, Compressed, and the Artifact That Looks Like Evidence

Compression can create image features that require examination before they are attributed to the subject.

What a raw file keeps and a JPEG discards

In a Bayer sensor, each photosite samples one filtered band and demosaicing estimates the other channels. A sensor-native raw file preserves more of the captured data and interpretation options than a rendered JPEG. Check the actual raw format and processing; not every digital camera uses a Bayer mosaic and not every raw file preserves untouched sensor samples.

A sensor-native raw file can retain the recorded mosaic while white balance remains an adjustable interpretation parameter. JPEG rendering embeds those choices in pixel values, limiting reversal. Preserve the original in either format and disclose processing; raw format alone does not establish that nothing changed.

Baseline JPEG uses 8 bits per channel. A 12-bit raw encoding provides 4,096 code values and a 14-bit encoding 16,384. Greater bit depth can preserve tonal headroom, but cannot guarantee recovery from clipping, noise, or inadequate exposure.

13.1Shoot raw for anything that will be examined, compared, or measured. Shoot JPEG only for orientation frames where the pixel values are not the evidence.

Two definitions of dynamic range, three stops apart

Dynamic range is where cross-examination gets sloppy on both sides. There are two published definitions and roughly three stops between them, a stop being a doubling or halving of light. Engineering dynamic range takes the low endpoint where the signal-to-noise ratio crosses 1; photographic dynamic range takes it at a signal-to-noise ratio of 20, adjusted for the sensor's circle of confusion. On one much-measured sensor the two figures are 12.37 stops and 9.00 stops. Same sensor, same settings, 3.37 stops of difference created purely by the choice of noise criterion. An opposing expert can say fifteen stops while you say eleven and you can both be telling the truth. A dynamic range figure without a stated noise criterion means nothing.

Check whether compressed raw is lossless

"Lossless compressed raw" is lossless in fact. "Compressed raw" is not, and neither are several format names a non-specialist reads as synonyms. Nikon's ordinary compressed format applies a lossy encoding before its entropy coding, reducing the distinct values from the analog to digital converter to a table of a few hundred to a few thousand entries; on a 12-bit sensor a 683-entry table retains about 16.7 percent of the discrete tonal levels. Sony's compressed format converts to an 11-bit tone curve and delta-encodes in 16-pixel blocks with 7-bit differences, which posterizes exactly where you least want it. Canon's compressed option quantizes a wavelet transform and lands 30 to 40 percent smaller than lossless. And Digital Negative, the archival raw container, is not automatically lossless either; its compression tag includes a lossy setting. "I converted it to Digital Negative" establishes nothing about data preservation.

What the compressor throws away, and in what order

Compression is worth understanding mechanically, because the artifacts are named and predictable. JPEG converts to a luminance-plus-color representation, subsamples the color, partitions the image into 8 by 8 blocks, applies a discrete cosine transform to each block, divides the resulting 64 coefficients by a quantization table, and entropy codes the result. Read the standard's sample luminance table and the policy is visible: the entry scaling overall brightness is 16, while the entries carrying the finest detail run past 100. The quantization table is a written record of what the camera decided to throw away. Real cameras use their own tables, so never speak of "the" JPEG quantization table as though only one exists.

The color side is more aggressive still. In the 4:2:0 subsampling used by most cameras and virtually every phone, one color value is shared by a two-by-two block of four pixels, so three-quarters of the color measurements are discarded before the transform even runs. Luminance is untouched. That asymmetry is why compression damage shows up as color error at edges, and why an opinion resting on subtle hue gradients rests on the first thing thrown away.

The Scientific Working Group on Digital Evidence publishes an artifact list in its compression guidelines: blocking, meaning pixel blocks coinciding with the macroblock size; banding, meaning visible steps in what should be a smooth gradient; local color distortion; and high frequency losses, in which edges go fuzzy and fine detail blurs. Notice what the list does not include. It does not name ringing or mosquito noise, and it contains no warning that an artifact may be mistaken for image content. The field's own governing guidance is thinner on this hazard than the hazard deserves, and saying so is a legitimate observation for an expert to make.

An artifact that looks exactly like a crack

Lossy compression can produce ringing, block boundaries, banding, and loss of texture. Those effects can resemble or obscure physical features. Compare the original, other frames, and compression structure before attributing a line to a crack or tool mark. Grid alignment is a diagnostic clue, not conclusive proof of an artifact.

13.2When you see a suspicious line in a compressed image, check whether it lies on the 8-pixel grid before you write a word about it.

The research for this book did not locate a case report or peer-reviewed forensic paper documenting the described misreading of a compression artifact as physical evidence. Treat the artifact discussion as engineering inference from documented mechanisms, not a reported case outcome. State that distinction in any opinion relying on it.

What the literature does supply is a quantified boundary, from fingerprints. The National Institute of Standards and Technology measured one-to-one fingerprint matching against compression ratio and reported true accept rates of 0.993 at 15:1, 0.988 at 20:1, and 0.982 at 30:1, concluding that compression up to 20:1 produces minimal negative effects and that beyond 20:1 the decline exceeds the specified limit. The Federal Bureau of Investigation did not use JPEG for fingerprint archiving at all; it commissioned a purpose-built wavelet codec and capped compression around 15 to 20 to 1. When a national laboratory needs that number, it runs the experiment.

The guidance is consistent with all of this. Lossy compression may be acceptable for documentation images such as scene and investigative photographs, and it is not recommended for images that will be subjected to forensic analysis or comparison. The working group's image categories document draws the same line by name: examination quality images should be captured in a lossless or uncompressed format at the highest resolution the device offers.

13.3Sort every planned frame into documentation or examination quality before you leave for the scene, and set the format accordingly.

The newer formats hide their damage better

High-efficiency image containers can hold images encoded in different ways. Determine the actual codec and settings before assessing losses. Some coding structures lack JPEG's fixed 8-pixel pattern, so the absence of that pattern does not establish intact detail. The author's artifact concerns are engineering inferences, not a demonstrated forensic characterization.

Neural denoising and enhancement can estimate detail not directly resolved in the input. Treat output as processed imagery even when written as a Digital Negative file. Preserve inputs and compare the result with independent images or examination where available. Do not assume plausible generated detail records a physical feature.

13.4Record in the chain of custody whether any neural processing touched the file, and treat a machine-generated Digital Negative as a processed image, not an original.

Chapter 13 Checklist: Format and Artifacts

Part Three. The Scene

Chapter 14Before You Leave

An incomplete inspection can leave important questions undocumented, particularly when access cannot be repeated.

Start from the question the imagery must answer

State the question the imagery must address and build a shot list from it. For a guard-position issue, document mounting features, witness marks, sight lines, warnings, identifiers, and relevant comparison equipment. Record what the photographs can establish about current condition and what additional evidence is needed for incident-time condition.

14.1Write the question the imagery must answer at the top of the plan before you write a single line of the shot list.

A plan is one page with four things on it: the question, the shot list built backward from the question, the equipment that list requires, and the constraints you already know about. Constraints are what turn a good plan into a possible one. Sunrise and sunset, if the case turns on what a driver could see. Tide and current, if the structure sits in water. The plant's shutdown window, because the line will not stop for you during production. The three hours the property owner agreed to, and not a minute more.

Who decides what you may photograph on site

Access is a legal question and it is not yours to answer. Someone negotiated your entry, and the terms of that negotiation govern your day. Know them before you leave the office.

A written site inspection protocol should tell you the date and the time window, the areas and systems in scope, who may attend, who may operate equipment, whether you may measure, whether you may test, whether you may remove anything, and what you may not photograph. Faces of employees, security systems, other tenants' property, and proprietary processes are commonly carved out. If nobody has written it down, ask retaining counsel to write it down.

Where entry comes by court order, the order controls, and the order's silence is not permission. Federal Rule of Civil Procedure 34(a)(2) governs entry onto land for inspection in federal civil cases, and Federal Rule of Civil Procedure 26(c)(1)(E) lets a court designate the persons who may be present while the discovery is conducted. Reading those provisions is counsel's work. Complying with them is yours.

Plan for limited return access

Plan to complete authorized coverage during the available visit. Repairs, disposal, changed conditions, or access disputes can prevent an equivalent return inspection. Record unfinished work and arrange follow-up through counsel when needed.

Carry two of everything that can fail

Redundancy is not gear enthusiasm, it is arithmetic. A camera body is a single point of failure standing between you and a scene that will not exist next month. Carry two bodies, and where you can, carry two bodies that take the same lenses and the same batteries. Carry more memory cards than you can imagine filling, and format them in the camera that will write them, not on a computer. Carry spare batteries for the bodies, the flashes, the triggers, and the light meter, and charge every one of them the night before. Do not delete a frame in the field. Do not reformat a card in the field. A card that is full is a card that goes in the labeled sleeve and stays there.

14.2Format every card in the body that will write it, fill it, then retire it to a labeled sleeve for the rest of the trip.

Your camera clock is an uncalibrated instrument

Verify how the camera maintains time, including any synchronization features, and compare it with a known reference. Record offset, time zone, and daylight-saving setting. Do not infer the camera's timing performance from a different clock component's specification.

There is a second problem underneath the first. Image metadata timestamps are plain text in the camera's local time with no time zone attached. The metadata standard did not add fields for the offset from Coordinated Universal Time until version 2.31, published in July 2016, and plenty of bodies built after that date still write nothing into them. A timestamp with no offset is ambiguous by as much as fourteen hours. If your timeline turns on whether a frame was captured before or after an event, the timestamp alone will not resolve it.

The fix takes ninety seconds and it belongs at the start of every session. Photograph a time display you can defend, a satellite receiver's readout or a network-synchronized phone or the United States government time page, in the same frame as, or immediately adjacent to, your first evidence frame. Do it again at the end of the session. Then compute the signed offset: camera clock minus true time. Two measurements, one at each end, give you drift across the session and let you state a bound on the error rather than a point estimate.

Location tagging records where you stood, not the subject

Decide your location tagging policy before you leave, and write the decision into the plan. Location tagging embeds the coordinates of the photographer, not the subject, and it can also record the direction the lens was pointing. That cuts both ways. It corroborates where you stood and when, which is useful. It also travels with every frame you produce, including frames shot on the same body in an unrelated matter on the same day. Whatever you decide, decide it in advance and never strip coordinates from an original afterward.

14.3Set the policy on location tagging before the inspection, record it in writing, and never remove metadata from an original file.

Two last items belong on the page before you close it. First, weather and light: check the forecast, and if the case involves visibility, check the sun's position at the hour that matters, because you cannot rephotograph a shadow. Second, personal protective equipment, site orientation, and the escort you will be assigned. An expert who arrives without boots and a hard hat gets sent to the parking lot, and the three hours run anyway.

14.4Pack the plan itself, on paper, and shoot from it.

Chapter 14 Checklist: Before You Leave

Chapter 15Overall, Midrange, Close-Up

A close-up records detail but may not establish location or context.

Use overall, midrange, and close-up views together. The close-up records detail, the midrange connects the detail to its surroundings, and the overall documents the scene. Missing a tier can leave an identification gap. Evaluate that gap with the remaining images, notes, and other evidence.

This is not a stylistic preference. It is the oldest working method in forensic photography, and it survives in the current guidance. The now-defunct Scientific Working Group on Imaging Technology built its impression photography guidance around documenting "the overall, midrange and close-up views of the area," and the sequence appears in the proposed Standard Guide for Crime Scene Photography published by the Organization of Scientific Area Committees for Forensic Science in June 2020. The reason the tiers exist is evidentiary, not aesthetic: each tier authenticates the tier below it.

Every close-up must trace back to an overall

Make each close-up traceable through a midrange view to an overall where practicable. Record identifiers and camera positions. Where a view is missing, explain how the remaining record identifies the item and location.

15.1Make every close-up traceable to an overall through at least one midrange frame.

The four-corner walk, and the walls behind you

For an interior, begin with views from each accessible corner toward the room, then cover near walls, ceiling, floor, and areas hidden by obstructions. Check overlap and gaps rather than assuming four frames cover every direction. Outdoors, document the perimeter and relevant approach positions at the required eye height.

Overlap adjacent frames by roughly a third for reviewable coverage, then check for gaps and occlusions. Overlap does not prove nothing was skipped. For three-dimensional reconstruction, use the overlap required by the method and translate the camera between positions to obtain parallax rather than only rotating it.

Photograph the sign that names the room

Orientation frames are the cheapest documentation you will ever make. Before entering any area, photograph the thing that names it: the room number, the door placard, the street sign, the bay number, the serial plate, the equipment tag, the mile marker. Those frames act as dividers in a file of two thousand images, and they convert a folder into a narrative that a paralegal, a mediator, or a juror can follow without you standing next to them.

The frame without the scale comes first

Now the scale rule, and note the ordering, because the ordering is mandatory language. The Organization of Scientific Area Committees guide provides that photographs should be captured with a scale whenever the relative size of an item is in question, and that if a scale is used, the photographer shall be certain a photograph is first captured without the scale. Without-scale comes first. The reason is that the scale is an object you introduced into the scene. The unscaled frame proves you concealed nothing beneath it and preserves the item in its found condition. The same sequencing appears in the older impression guidance: overall, midrange and close-up views without scales and markers, then the same views with markers and scales added.

15.2Shoot the no-scale frame and the scale frame of every item, in that order, every time.

For direct planar measurement, place the scale in the subject plane, align the sensor plane, use stable support, and record geometry. A depth mismatch changes scale according to the perspective model; account for that difference rather than applying a scale from another plane without correction.

What your photograph log has to record

The log itself takes discipline and pays it back at deposition. For each frame or short run of frames, record the frame number, the time, the subject, the camera position or direction, the lens and focal length, and one line of note. Write it as you go, before you move the tripod, not from memory in the hotel that night. Three columns and a pen beat a perfect memory, and the log is what lets you answer "which way were you facing" without guessing.

Photograph what does not matter yet

Document relevant comparison items, adjacent conditions, and locations where an expected feature is absent. Photographs can support an absence claim, but records and witness evidence may also matter.

Cases change theory. The defect you were retained to examine gets conceded and the case becomes a notice case, and notice lives in the frames you took of things that did not matter yet.

I have never once regretted an extra hundred frames. I have regretted the missing one many times.

15.3Photograph the thing you are confident is irrelevant, and log it like everything else.

15.4Log the frame number, direction, and subject before you move the camera, not at the end of the day.

Present overall, midrange, and close-up views in an order that connects scene, location, and detail. Explain the observation and limits at each step.

Chapter 15 Checklist: Overall, Midrange, Close-Up

Chapter 16Photographing Injuries and People

A photograph of an injury is evidence. A photograph of a person is a relationship. You have to manage both at once, and the second one is harder.

Consent is a condition, not a form. It has to hold at the start of the session and still hold at the end. Explain what you are photographing, what will be visible, who will see the images, and that the person may stop at any time, decline any frame, and ask for a chaperone. Then do all of that. Photograph only what the injury requires and drape the rest. Keep the frame tight enough that the image proves the injury without exhibiting the human being, and shoot the version you would be comfortable projecting in a courtroom with the plaintiff's family in the gallery, because that is where it goes. Where the imaging happens at a defense medical examination, the scope is set by agreement or by order, and you photograph inside it and nowhere outside it.

Why a flash on the camera hides the injury

Near-axis flash can reduce visible texture and create glare on skin. Inspect highlights and surface detail at the scene. Compare off-axis and diffuse lighting, and preserve the original capture when processing a copy.

SWGDE describes off-axis direct lighting and cross-polarization to manage reflections. Cross-polarization can reduce sheen on skin. Compare it with an unpolarized frame and document the lighting used rather than treating it as universally preferable.

Meter for the skin that carries the evidence

Meter and bracket for the actual skin and injury, check the relevant histogram region, and protect required detail from clipping and noise. Use raw capture, suitable illumination, and a color reference for color-critical comparisons. Skin tone alone does not determine the metering error; framing, background, illumination, and metering mode also matter.

16.1Put a color reference target in at least one frame of every injury series, and record the light source you used.

Bodies are curved and scales are flat

Scale on the body follows the same geometry as scale anywhere else, with one complication: bodies are curved. The entire scale must sit in the plane of the feature you are measuring, adjacent to it, not covering it, and the sensor plane must be parallel to that local plane. On a forearm or a shin, the plane changes over a few centimeters, so photograph the feature in sections rather than fighting the curve in one frame. Adhesive-backed and flexible versions of the American Board of Forensic Odontology No. 2 photomacrographic scale exist for exactly this reason. Take the no-scale frame first, then place the scale. And know the limits of the tool you are using: a National Institute of Standards and Technology dimensional review of commercially sold scales found the linear graduations reliable across vendors but the printed circles, the feature relied on to correct oblique perspective, out of specification at every vendor tested. Use the legs for measurement. Do not build an opinion on the circles without verifying the particular scale.

16.2Take the no-scale frame first, then place the scale in the plane of the injury, never across it.

Do not date a bruise from its color

Do not date a bruise from photographic color alone. The systematic review literature cited earlier reports unreliable age estimates from clinical appearance and photographs. The cited Thavarajah, Vanezis and Perrett study also identifies pigmentation-related limits in detecting yellowing. Capture and display conditions add uncertainty. A treating clinician's role does not remove the need for a validated basis for any timing opinion.

Control variables in an injury series

Use consistent camera, lens, focal length, distance, lighting, background, framing, and scale placement across injury sessions. Record unavoidable differences and assess their effect before attributing an apparent change to the injury. Consistency improves comparability but does not alone prove biological change.

16.3Fix focal length, distance, lighting, and background at the first session and reproduce them exactly at every session after.

Record the day, do not direct it

Day-in-the-life documentation is closer to filmmaking than to evidence photography, and it draws its own objections about staging, cumulativeness, and prejudice. How far to push it is trial counsel's judgment, and the presentation questions come later in this book. Your job on the day is to record what happens without directing it, log what you did and did not stage, and resist the temptation to build the most affecting version of the truth.

Determine whether federal medical privacy rules apply

HIPAA rules apply to covered entities and, where specified, business associates. The definitions and applicability provisions appear in 45 CFR 164.104. Determine the expert's role and relationships before deciding whether those rules apply to the imaging work. Do not assume that retention as an expert creates an exemption.

Correct the companion error while you are at it. The de-identification provision at section 164.514 lists eighteen identifiers that must be stripped, and item (Q) on that list is "full face photographic images and any comparable images." That list is not a definition of protected health information. It is a list of identifiers whose presence prevents information that is already protected health information from qualifying as de-identified. Saying "photographs are protected health information because they are on the eighteen-identifier list" inverts the regulation. The same photograph has two legal characters depending on who holds it: in the hospital's chart it is protected health information held by a covered entity, and in your file it is a photograph.

16.4Get the protective order's imaging and retention terms from retaining counsel in writing before the first session, and file that email with the case.

Chapter 16 Checklist: Injuries and People

Chapter 17Photographing Parts, Machines, and Failure Surfaces

Every failed component carries two records: the one the failure wrote, and the one the handling wrote afterward. Your job is to capture the first before anyone adds to the second.

Do not clean or disturb a part before documenting its as-found condition and resolving the examination protocol. Assess debris, films, transfer, and dust patterns in context, and obtain testing where needed. Coordinate any cleaning with counsel and the relevant specialists because it can alter evidence.

17.1Do not clean the part, and do not mate the fracture halves.

Photograph the box before you open it

Document as-found before anything moves, and "anything" includes the box. Photograph the shipping container closed, with its labels and seals. Photograph the evidence tags, the chain of custody form, the packing material, and the way the part sits inside it. Then photograph the part in the packaging before lifting it out. If the part arrives assembled, photograph the assembly from six sides before a single fastener turns. Index marks, witness marks, alignment scribes, and the relative positions of mating components are all information that exists only until the first thing moves.

Use lighting to document surface relief

The features you are usually there to record fall into a few families, and each has its own lighting demand. Fracture surfaces carry beach marks, ratchet marks, shear lips, and origin regions, and every one of those is relief, not color. Wear patterns are polish, scoring, and directional texture. Witness marks are the impressions one part leaves in another, and their value lies in where they are and which way they run. Thread engagement is countable: the bright band where threads bore load and the dull band where they did not, and the number of threads standing proud of the nut. Fastener marks tell you about assembly and disassembly history, including socket and wrench marks on the flats, paint or lacquer witness across a joint, and torque stripe alignment.

Oblique light can convert small height differences into visible shadows. Under the stated geometric model, shadow length equals feature height divided by the tangent of the illumination angle. Record the angle and surface geometry, and compare lighting directions. Shadows are one way to document relief, not the only one.

Two consequences follow and both get asked about. First, shadow length is not a measurement of depth unless you know and recorded the angle, so record the angle. Second, the lower the angle, the greater the exaggeration, which is why you shoot the same feature at more than one angle and say so.

17.2Record flash distance, angle from the surface plane, clock position, and manual power for every oblique frame.

Resist the urge to name a standard angle, because there is not one. The Scientific Working Group on Digital Evidence specifies a criterion rather than a number: place the light at a low enough height and angle to cast a shadow into the subject, and adjust the angle to produce the appropriate contrast. The correct angle depends on the depth of the relief, and an expert who testifies to a fixed universal number invites impeachment. Documented working values do exist in the practitioner literature for impression photography, at 25 degrees and 45 degrees, and near-grazing angles are used for the shallowest relief. Use them as starting points, not as a rule.

The footwear and tire guidance calls for ambient-light photographs and oblique lighting from several angles, including the four cardinal points. Applying that approach to parts can reveal relief obscured by a single direction. Visibility also depends on feature shape, reflectance, and other illumination.

Use manual flash power, not automatic metering

Use manual flash settings for controlled comparisons and record power, distance, angle, modifiers, and exposure. Automatic metering can vary output on reflective surfaces. If used, evaluate that variation rather than assuming that automatic capture cannot be documented or repeated.

Why stopping down ruins a close-up frame

At high magnification, effective aperture can be smaller than the marked aperture, increasing diffraction while geometric depth of field remains shallow. Calculate the effective aperture for the lens and magnification and test the resolution needed for the feature. Do not attribute a soft frame to diffraction without considering focus and motion.

If a single frame cannot resolve the required depth, consider focus stacking on stable support with the part immobilized. Check the resulting composite for artifacts and preserve the source sequence.

17.3Preserve every source frame of a focus stack and disclose the stack as a stack.

A tilted sensor plane changes shape, not just size

For direct measurements, align the sensor with the measured surface and place the scale in its plane. Tilt and perspective can affect dimensions and shape; assess the actual geometry and uncertainty. Preserve lossless originals and compare suspicious features across frames before attributing them to the part.

Plan and obtain authorization before disassembly

Disassembly can alter component relationships or damage evidence. Document the as-found condition and have counsel resolve notice, protocol, attendance, and authorization requirements before work begins. Do not let an operator start turning fasteners outside that protocol.

Photograph each step twice: once with the tool in position and the fastener untouched, and once immediately after the component comes free, showing both mating faces. Number the steps and number the parts, and photograph every removed item with its own label and its own bag before it goes into the bag. Run video of the whole disassembly on a locked-off camera as a continuous record while you shoot stills, because the video answers "what order did you do that in" without argument. Bag and tag as you go. Never combine two removed items in one container.

17.4Photograph every disassembly step before the tool touches the fastener and again the moment the part comes free.

Chapter 17 Checklist: Parts, Machines, and Failure Surfaces

Chapter 18Difficult Scenes: Fire, Water, Height, and Dark

The difficult scene is not the one that is hard to photograph. It is the one that is destroying the evidence and endangering you at the same time, on a schedule nobody consulted you about.

Fire, marine, elevated, and confined scenes can combine perishable evidence with hazardous or restricted access. Assess the actual hazards and preservation needs, plan authorized access, and document gaps. Do not assume another visit will reproduce the same conditions.

Fire writes in char, soot, and calcined surface

A burned structure can retain char, soot, calcined material, and other evidence affected by heat, ventilation, suppression, and subsequent handling. Document fragile surfaces before disturbance and avoid treating any one pattern as a complete record of fire duration or gas movement.

So the sequence is fixed. Photograph the exterior in a four-corner walk before anyone re-enters, then each elevation, then the ground and debris field outside the structure. Move inward compartment by compartment, working from the areas of least damage toward the areas of greatest damage, and photograph each compartment overall, midrange, and close-up before you photograph any detail within it. Photograph every protected surface, meaning every place where an object shielded the material beneath it, because a protected surface is a shadow of the fire's own geometry and it is the first thing lost when the object is moved. Then, and only then, begin layer removal, photographing each layer before you take it off. Debris excavation is destructive testing. The other side gets to see every step.

18.1Photograph the protected surface before you lift the object that created it, and photograph it again after.

Soot is the hardest thing you will ever meter

Exposure at a fire scene fights you in a specific way. Soot is one of the lowest-reflectance surfaces you will ever meter. A reflected-light meter is calibrated to render whatever it sees as a middle tone, so pointed at a charred wall it demands more exposure and gives you gray mush where the evidence is a difference between deep black and slightly less deep black. Meter manually, bracket deliberately, and put a gray card and a color reference target in at least one frame of every compartment. Color fidelity is not decoration here. The distinction between clean burn and soot deposit, between oxidized and unoxidized metal, between thermal and mechanical damage, often lives in hue and in a narrow band of dark tones.

Char relief responds to oblique light the same way a tool mark does. The current standards language does not give a fixed angle; it gives a criterion, which is to place the source low enough to cast a shadow into the feature. Set the flash off the camera, work the angle until the relief reads, and record the angle you used, because shadow length is not a measurement of depth unless the angle is known.

Painting a dark interior with the lens covered

In a dark burned interior, a documented painting-with-light method can help record coverage. Use stable support, manual settings, a planned flash sequence, and an opaque lens cover between exposures where required. Log positions and pops and review for stray illumination and visible operator movement.

Water bends the light before it reaches the lens

Water and a flat housing port change apparent geometry. Place the scale in the subject plane, evaluate backscatter with off-axis lighting, and document color references under the capture conditions. Underwater photogrammetry requires a model and calibration or validation that account for refraction. Assess the actual housing, water, and method.

Recovered hardware has a clock running on it

Recovered marine hardware has a clock on it. Salt water keeps working after recovery, so document the as-found condition wet, in place if you can reach it, and document again immediately on recovery, before anyone rinses, brushes, or preserves anything. Photograph the fastener before the wrench touches it.

Where was the load path

Document the entire load path in an elevated or rigged system, linking anchors, connectors, terminations, and attachments. Ground-level images may not resolve small features at height. Use safe, authorized access or suitable remote imaging and identify any unresolved gaps. The load path is one part of the failure analysis, not a single decisive question.

18.2Document rigging as found, and never adjust a component to improve a photograph.

Tether cameras and accessories at height. Tie in independently of the evidence, using an access and fall-protection system assessed for the task. Do not use a component under investigation as the anchor for documenting that component.

A confined space is an atmosphere problem first

Do not enter a permit-required confined space without the required controls, trained personnel, monitoring, and rescue arrangements. Have qualified personnel assess ignition risks before taking electrical equipment into a potentially flammable atmosphere. Decline entry when the required safety conditions are not met.

Confined spaces can require wide framing. Record viewpoint, lens, and scale, and use additional views where needed. Wide focal length alone does not determine perspective or establish that distance is misrepresented.

18.3Write the hazard, the protective equipment, and the access method into the photograph log for every difficult scene, on the same line as the frame numbers.

The unifying principle is that protecting yourself and protecting the evidence are the same discipline practiced in two directions. Both require you to slow down at the exact moment the scene is pushing you to hurry. Both require a sequence decided before you arrive. And both are judged later by people who were not there, reading a log written by someone who was.

Chapter 18 Checklist: Difficult Scenes

Chapter 19Night, Visibility, and the Honest Photograph

A night photograph can reveal detail an observer could not perceive and can also omit visible detail. Evaluate capture, processing, display, and observer conditions before using it to support a visibility opinion.

The camera pools light no eye can gather

A long camera exposure integrates light over a different interval from human vision and can reveal detail unavailable during a brief observation. The effect depends on the scene and viewing task. SAE paper 2017-01-1366 describes a timed-observation method using roughly one-quarter-second viewing intervals; apply its findings within the tested conditions.

Your display cannot carry the range the scene had

The reproduction chain cannot carry the scene. The central methodology paper in this field, Society of Automotive Engineers paper 2016-01-1463 by Suway and Welcher, calibrates photographs and video for display by quantitative measurement rather than subjective assessment, and its abstract concedes in its own words that digital sensors and displays cannot reproduce the full dynamic range visible to human eyes. The people who built the method say so. You should say so too, out loud, before opposing counsel says it for you.

Adaptation is slow to build and fast to lose

Adaptation affects nighttime sensitivity. Evaluate prior light exposure, its intensity and duration, and the observer's visual task. Laboratory bleaching results do not establish a driver's threshold change from the mere presence of a dashboard, sign, or headlamp.

Rod-mediated scotopic vision differs from photopic vision in contrast sensitivity, acuity, and color perception. A nighttime roadway may involve mixed lighting and cone activity. Establish the relevant conditions before concluding that a color photograph shows information unavailable to the driver.

19.1State in the exhibit caption that the image was made by a camera, not by an eye, and that the two are different detectors.

Courtroom viewing conditions can differ from the driver's conditions. Evaluate luminance, adaptation, viewing duration, and display calibration rather than assuming all jurors are photopic and all nighttime drivers scotopic.

Match the conditions that change the number

Match and document conditions relevant to visibility. SAE paper 2019-01-1005 reported negligible full-moon contribution to visibility distance in its tested low-beam conditions. Do not generalize that result to every scene. Record moon position, clouds, roadway lighting, and pavement conditions and assess their effects in the actual reconstruction.

Headlamp beam pattern, aim, lamp type, lens condition, and bulb condition affect target illumination. Photograph the actual lamps and measure aim where possible. The cited vehicle-specific mapping methods support evaluating the actual configuration. If a substitute vehicle or lamp is used, identify and assess the differences.

Retroreflective material ages, and the aging is measurable rather than rhetorical. There is a published body of work on quantifying retroreflective materials from digital imagery, on the performance of conspicuity tape as a function of observation and entrance angle, and on the systematic degradation of retroreflective materials for testing purposes. A defense exhibit shot against fresh tape is not an exhibit of the trailer as it existed. Measure the actual material or match its condition, and disclose which you did.

19.2Record moon phase, cloud cover, precipitation, roadway lighting status, and pavement condition for the incident night and for the night you shoot, side by side, in the report.

The night exposure is chosen, not discovered

The calibration methods are old and they are honest about their own limits. The foundational paper, Society of Automotive Engineers 890730 by Holohan, Billing, and Murray, produced what it called a photograph that accurately illustrates the limits of perception, by having an observer view signs of varying shades of grey at the site under appropriate conditions and then selecting the correct density from a range of prints. Read that method again. The exposure is chosen. It is chosen against an observer standard, which is the honest part, but it is chosen, and absent that observer step the density of your night print is arbitrary. The video analogue, paper 960895, adds the point most experts miss: it calibrates recording and playback, using a hand-held grey scale chart on location. The courtroom monitor is inside the validated method. An uncalibrated display in the courtroom is outside it.

A parallel line of work treats the camera as a photometer, with published calibration methods for luminance estimation from still cameras and from video. That work is what allows an expert to say a measured quantity rather than an impression. It also imposes an obligation: if you use the camera as an instrument, you must state its linear response range and the settings at which you calibrated it, the same way you would for any other instrument.

Two warnings from inside the field are worth more than any warning from outside it. The abstract of paper 870600, by Olson, says that while such reconstructions can be helpful, they can also be very misleading. And paper 900369 frames the evidentiary difficulty precisely: the determination of what would have been visible to a reasonably alert person must be made with proper consideration of both inter-person and intra-person variability. Neither of those sentences was written by a defense lawyer. Both were written by the people who built the discipline.

19.3Shoot from the driver's eye position inside the subject vehicle, and record the seat and mirror positions you used.

19.4If you cannot match a condition, substitute deliberately, measure the substitution, and disclose it in the caption rather than in a footnote.

Print the conditions on the face of the exhibit

Place the essential conditions and limitations on the night exhibit and provide the full method in the report. Identify date, time, lighting, camera position, exposure, calibration, and any observer procedure. Missing information limits interpretation but does not make every documentary use of the image worthless.

Chapter 19 Checklist: Night and Visibility

Chapter 20The View From Above

Drone documentation raises aviation, access, privacy, and evidentiary questions. Address both the flight and the imagery.

The certificate you need before you touch the controls

Start with certification, because it is the first question and the easiest one to fail. Civil small unmanned aircraft operations in the United States are governed by Title 14 of the Code of Federal Regulations, Part 107, which reaches aircraft weighing less than 55 pounds on takeoff including everything on board or attached. Section 107.12 prohibits manipulating the controls without a remote pilot certificate carrying a small unmanned aircraft systems rating, or direct supervision by a holder. Section 107.61 sets eligibility: at least 16 years old, able to read, speak, write, and understand English, with aeronautical knowledge established either by the initial knowledge test or, for a current Part 61 certificate holder, by the training specified for that path. Verify every section number in this chapter against the electronic Code of Federal Regulations before you rely on it, because this part moves.

Currency is the part practitioners get wrong. Section 107.65 is not a recurrent-test rule. Within the previous 24 calendar months the remote pilot must have accomplished one of several alternatives: passed an initial knowledge test, completed recurrent training, or, for a current Part 61 certificate holder, completed the training specified for that path. The recurrent knowledge test was replaced by recurrent training. The 24-month interval was not changed. Know which alternative you are relying on, because you will be asked.

Registration carries the same trap. Under Part 48, the exemption for aircraft weighing 0.55 pounds or less applies only to aircraft operated exclusively under Title 49 of the United States Code, section 44809, the recreational provision. An expert flying a sub-250-gram aircraft to document a scene is operating under Part 107 and must register it regardless of weight, with the unique identifier legibly displayed on an external surface. Remote identification under Part 89 has applied since September 16, 2023, satisfied by built-in remote identification, by a broadcast module flown within visual line of sight, or inside a Federal Aviation Administration Recognized Identification Area. The date many operators quote, in March of 2024, was the end of a published enforcement discretion policy, not a change to the regulation.

20.1Register every aircraft you fly for a case, whatever it weighs, and photograph the identifier on the airframe as your first frame of the day.

How high, how fast, and whose airspace

The operating limits sit in section 107.51. Groundspeed may not exceed 87 knots, which the rule itself expresses as 100 miles per hour. Altitude may not exceed 400 feet above ground level unless the aircraft is flown within a 400-foot radius of a structure and does not go higher than 400 feet above that structure's immediate uppermost limit. Minimum flight visibility is 3 statute miles, and the aircraft must remain 500 feet below and 2,000 feet horizontally from clouds. Section 107.31 requires that it stay visible throughout the entire flight. Section 107.41 requires air traffic control authorization in Class B, C, and D airspace and in the surface area of Class E designated for an airport; Class G requires none, and the Low Altitude Authorization and Notification Capability system supplies authorization at or below 400 feet at hundreds of airports.

Two limits matter disproportionately to scene work. Night operation under section 107.29 no longer requires a waiver, provided the remote pilot completed the knowledge test or training after April 6, 2021 and the aircraft carries anti-collision lighting visible for at least 3 statute miles. Only the lighting requirements are waivable; the training requirement is not. And section 107.145 governs flight over people inside moving vehicles: absent a closed or restricted access site with notice to those inside, the aircraft must not maintain sustained flight over them. Documenting an open roadway scene is squarely a section 107.145 problem, and transient transit is the only unwaived option. Note also that section 107.23, careless or reckless operation, does not appear on the waiver list. There is no waiver to operate carelessly.

Beyond visual line of sight operations still require a section 107.31 waiver, because Parts 108 and 109 are marked reserved and the proposed rule published in August 2025 remained proposed as this was written. And the falsification provision that used to sit at section 107.5 is now reserved, consolidated into sections 3.401 through 3.405. Any checklist you inherited citing section 107.5 is stale.

Do not treat aerial-surveillance cases as permission to fly

The Fourth Amendment aerial surveillance cases are not your rule of decision. California v. Ciraolo, 476 U.S. 207 (1986), Dow Chemical Co. v. United States, 476 U.S. 227 (1986), and the plurality in Florida v. Riley, 488 U.S. 445 (1989), all address government observation from navigable airspace.

The cited Fourth Amendment decisions concern government conduct. A privately retained expert should not treat them as authorization for a flight. Ask counsel whether state action, property rights, privacy law, or other restrictions apply to the actual assignment.

What reaches you is state privacy tort, principally intrusion upon seclusion; common-law trespass, informed by the reasoning in United States v. Causby, 328 U.S. 256 (1946), that a landowner must have exclusive control of the immediate reaches of the enveloping atmosphere; and state statute. Altitude authorization is not a trespass defense.

Long Lake Township v. Maxon, decided by the Michigan Supreme Court on May 3, 2024, is the case most often described incorrectly. It is an exclusionary rule case, holding that the exclusionary rule may not be applied to civil enforcement proceedings that effectuate local zoning and nuisance ordinances and seek only prospective, injunctive relief. The court expressly declined to decide whether the warrantless drone surveillance was a Fourth Amendment search. Anyone who tells you Long Lake Township held that warrantless drone surveillance is a search has not read it.

20.2: Have counsel identify the authority and restrictions for the planned flight. Do not treat the aerial-surveillance decisions as a substitute for that review.

The law that reaches you is the state statute

State anti-surveillance statutes are the live risk, and they are in force. In National Press Photographers Association v. McCraw, 90 F.4th 770 (5th Cir. 2024), the Fifth Circuit reversed the district court and upheld the Texas statute, reasoning that the law regulates not what image is captured but where it is taken from and how, and that drone operation is not inherently expressive conduct. Sources written before 2024 reporting the statute as struck down are wrong. Florida's statute, section 934.50, reaches private persons directly and shifts attorney fees. Oregon's private-actor provision turns on repetition and notice: an owner may sue where the operator flew over the property at least once before and the owner then objected, with treble damages and no altitude threshold. Nevada sets a 250-foot threshold with prior notice and carves out licensed land surveyors. California Civil Code section 1708.8 reaches entry into the airspace above the land, and its constructive invasion provision reaches capture by any device regardless of physical trespass.

20.3Before the flight, read the statute of the state you are standing in, and write the exception you are relying on into the engagement file.

What the overhead view shows that the ground cannot

An overhead view can document spatial relationships not clear in ground-level photographs. An oblique aerial can help examine obstructions, but a sight-line opinion requires the relevant eye position and geometry. Surveyed control and validated processing can support measurements. Explain viewpoint and limits rather than assuming the jury needs no instruction.

Saying the drone took the picture is not foundation

Foundation is where careless aerial work dies. Federal Rule of Evidence 901(b)(9), authenticating a result produced by a process or system, is the workhorse for drone imagery. No decision was located applying it to drone footage, so treat what follows as analysis and not as authority: a conclusory foundation invites the objection that nothing was established about camera reliability or system specification. It is not enough to say the drone took the picture. Establish the aircraft and sensor make and model, firmware version, calibration status, satellite lock quality, how the imagery was written and transferred, and hash verification at acquisition. Rules 902(13) and 902(14) let you avoid a live foundation witness, but only with advance notice.

20.4Preserve flight logs and telemetry as evidence, not as an application cache.

Flight logs, telemetry, and raw files are electronically stored information. Reformatting the card after export, letting a cloud logging account lapse, or producing only the finished orthomosaic while discarding source frames are realistic exposures under Federal Rule of Civil Procedure 37(e). Preserve both altitude records and know the difference: barometric altitude is referenced to a takeoff-point zero, satellite altitude to mean sea level, and section 107.51 is written in feet above ground level. An opponent who catches you conflating them has a cheap and effective cross.

Chapter 20 Checklist: Aerial Documentation

Chapter 21Three Dimensions

The research for this chapter located no decision squarely addressing the listed three-dimensional methods. That search result does not remove the court's gatekeeping role or establish that no relevant decision exists. Build a reliability record for the specific method and application.

What structure from motion does with your photographs

Technique first, because your reliability record is built out of technique. Structure from motion recovers camera positions and a three-dimensional point set from ordinary overlapping photographs. The pipeline is published and inspectable: detect features, match them across images, solve for camera poses and point coordinates in a bundle adjustment, then fuse depth into a dense cloud. Nothing about it is exotic. Everything about it depends on how you shot.

Overlap is the first published number. The Metashape manual specifies eighty percent forward and sixty percent side overlap for aerial capture, and sixty to seventy percent for close-range work. Pix4D's planning guidance sets a general case of at least seventy-five percent frontal and sixty percent side, rising to ninety percent for large vertical objects. For an object you orbit, the figure is one image every 5 to 10 degrees, roughly 36 to 72 images per circuit. That converts directly into a shooting plan for a damaged vehicle.

The capture rules are equally concrete. Prefer a fixed focal length; if you use a zoom, set it to an end stop so the setting is repeatable. Keep the sensitivity setting, marked ISO on every camera, at its lowest value, choose an aperture deep enough to hold the object sharp, and keep the shutter fast. Shoot raw files, convert losslessly, and never crop or geometrically transform the images: the software solves for one consistent lens model per camera, and any per-image remapping breaks that assumption.

Untextured, reflective, transparent, moving, or strongly changing surfaces can frustrate feature matching. Specular highlights need not track fixed surface points. Check reconstruction completeness and accuracy on the actual surfaces rather than assuming either success or inevitable failure from a surface label.

21.1Photograph a damaged vehicle in full orbits at 5 to 10 degree intervals, at three heights, before you photograph anything in detail.

Nothing in the photographs fixes the size of anything

A purely image-based reconstruction is determined only up to a similarity transform: position, orientation, and scale are arbitrary, and nothing in the images fixes the size of anything. Scale has to be imported, through certified scale bars oriented in several directions or through surveyed control points. And a subset of those points must be withheld from the solution and used only to measure residual error. A model validated only against the points used to constrain it is not validated at all.

How accurate photogrammetry is, in published numbers

In SAE paper 2010-01-0065, Randles and colleagues reported hands-on crush measurements differing from a total-station baseline by 0.6 centimeters with a standard deviation of 1.4, and photogrammetry by 0.1 centimeters with a standard deviation of 1.0. Paper 2019-01-0423 reported evidence locations within 3.0 inches and consistent results from five analysts. These are study-specific results, not accuracy guarantees for another reconstruction. Validate the case measurements separately.

Read the scanner specification with its conditions attached

Terrestrial laser scanning is the other route, sweeping a beam over the scene and recording range and angle for millions of points. Read the specifications with care. One instrument, as tabulated in a peer-reviewed laboratory study, publishes distance accuracy of 1 millimeter plus 10 parts per million at sixty-eight percent confidence, for a single-shot measurement to a surface of eighty-nine percent reflectance. Sixty-eight percent confidence is one standard deviation; a ninety-five percent figure would be roughly double. Eighty-nine percent reflectance is not a black tire, wet asphalt, or dark clothing.

That study also found the instrument stayed inside its manufacturer specification while showing clear systematic error components, including a striped pattern with discontinuities of about 2 millimeters at 20 meters. Systematic error does not average out with more points. Random noise does. An expert who reports a measurement as though millions of points had washed the error away has misunderstood the instrument.

Geometry compounds it. Beam divergence of half a milliradian grows the footprint by roughly half a millimeter per meter, so every returned point is the centroid of an illuminated patch and edges become mixed returns straddling foreground and background. Registration is a separate error budget again, compounding across setups, whether you register on targets of known geometry, by cloud-to-cloud matching, which fails predictably in a featureless corridor, or by the instrument's own tracking. Instrument performance is characterized by ASTM International test methods E2938 and E3125.

21.2Archive point data in the open interchange format specified by ASTM E2807, so another expert can independently examine what you produced. Note the naming confusion rather than repeating it: E57 is the committee, and also the common name of the point cloud format, but the format itself is specified by E2807.

What a tablet scanner can and cannot carry

The sensor in current Apple devices emits an 8 by 8 array diffracted into 3 by 3 grids, 576 points in total, with a stated maximum range of 5 meters. Against 2 million points per second, the envelope is obvious. Published evaluations give roughly plus or minus 1 centimeter on small objects and plus or minus 10 centimeters across a 130 meter cliff. Society of Automotive Engineers paper 2022-01-5083 compared a tablet scanner against a terrestrial scanner across ten vehicles and found an average difference of plus or minus 0.4 inch, with less than one percent error in the resulting change in velocity, called delta-V. Against that, a laboratory comparison could not produce an evaluable mesh at all on small objects, and noted that black is filtered out. Most consumer applications deliver a mesh rather than exportable raw points, which is fatal wherever the raw data is the deliverable.

The same caution applies to the view-synthesis methods now being marketed for reconstruction: they optimize photorealism, their headline metrics measure image similarity rather than geometry, and one published comparison found average distance differences around 1.3 meters on vertical surfaces. A photorealistic render is not a measurement.

The photogrammetry decisions are deference, not scrutiny

In United States v. Quinn, 18 F.3d 1461 (9th Cir. 1994), the court approved photogrammetric height testimony because the district court found the process nothing more than computer-assisted calculation involving no novel or questionable technique, and because the defendant pointed to nothing calling its reliability into question.

That is a burden-of-production ruling, not a reliability adjudication. United States v. Johnson, 114 F.3d 808 (8th Cir. 1997), contains no Rule 702 analysis at all, because admissibility was never challenged on appeal, and United States v. Kyler, 429 F. App'x 828 (11th Cir. 2011), is unpublished and was reviewed for plain error.

On the civil side, Chapman ex rel. Estate of Chapman v. Bernard's, Inc., 167 F. Supp. 2d 406 (D. Mass. 2001), is the leading federal decision, and its reliability holding runs one sentence: applying mathematics to photographs to derive measurements appears reasonable and does not strike the court as junk science. No error rate. No validation study. No factor analysis.

The most substantive treatment is State v. Matthews, 479 Md. 278, 277 A.3d 991 (2022), where an examiner performed reverse projection photogrammetry on scene with a calibrated height chart. The court held that the unknown degree of uncertainty in the estimate went to weight rather than admissibility, over a dissent. Make one terminology correction while you are there: neither Quinn nor Johnson uses the phrase reverse projection, and both describe scaling within a single image from objects of known size. Classical reverse projection requires re-photographing the scene with a reference of known height. That is what Matthews did.

21.3Never represent that photogrammetry or laser scanning has been searchingly validated by the courts. Say what the decisions hold, and say it first.

As for scanning itself, the negative finding rests on more than a failed search. The forensic community's own 2025 compilation of legal support for image examinations cites no case involving three-dimensional scanning, laser scanning, or point clouds. Those terms do not appear in it. State it the way it should be stated: no reported decision was located, and the leading compilation cites none. Not that none exists.

21.4Build the reliability record the courts have not built for you, and put it in the report before anyone asks.

Document the instrument and its specification conditions, capture geometry, settings, validation checkpoints, registration statistics, measurement uncertainty, and preserved source data. These support reliability review under Rule 702 but do not guarantee admission or shift the proponent's burden to the opponent.

Chapter 21 Checklist: Three-Dimensional Capture

Part Four. The Record

Chapter 22Video Is Not Photography

A photograph measures a moment. A video measures time, and time is the thing people get wrong.

Choose exposure, focus, geometry, lighting, color, scale, and timing controls appropriate to the video analysis. Timing errors can invalidate a speed calculation, but so can spatial calibration, motion blur, or incorrect feature identification. Assess the full measurement method.

Frame rate is a fraction, not a round number

Start with frame rate, because nothing downstream works until you know it. The rates people say out loud are 24, 30, and 60 frames per second. The rates cameras run are often 24000/1001, 30000/1001, and 60000/1001, which come out to 23.976, 29.970, and 59.940 frames per second. This is not a manufacturing tolerance. It is a deliberate 1000/1001 slowdown adopted when color was added to American analog television, so that the color subcarrier would sit in the right relationship to the sound carrier already in the air. Title 47 of the Code of Federal Regulations, Section 73.682, in the 2010 edition, states it in plain regulatory language: the vertical scanning frequency "corresponds nominally to 60 Hz (the actual value is 59.94 Hz)." Cite the 2010 edition, because the current text has removed the analog values and incorporates other standards by reference.

A file of 108,000 frames at 30000/1001 frames per second is 3,603.6 seconds long, not 3,600. Call it 30 frames per second and you have under-reported elapsed time by 3.6 seconds in every hour, which is one part in 1,001. Speed equals distance divided by elapsed time, so a shortened denominator inflates the answer by exactly one tenth of one percent. A true 60 miles per hour reads as 60.060.

22.1Write the frame rate into your notes as a fraction, never as a decimal, before you compute anything.

The 29.97-versus-30 error is about one tenth of one percent. Correct it, then evaluate variable timing and other uncertainties. Its materiality depends on the question and tolerance, not a universal ranking of video errors.

The shutter angle that looks right measures wrong

At a fixed frame rate, shutter angle determines exposure duration. The 180-degree convention gives 1/48 second at 24 frames per second, 1/60 at 30, and 1/120 at 60. Evaluate the resulting blur against the measurement tolerance rather than rejecting that setting for every measurement.

Work the numbers. A 50 mm lens on a sensor with 5.0 micrometer pixels, aimed at a car crossing the field of view at 25 meters per second, which is 55.9 miles per hour, from 30 meters away. One pixel covers 3.000 millimeters of that car. At 1/60 second the car travels 416.7 millimeters during the exposure, which is 138.9 pixels of smear. At 1/1000 second it is 8.3 pixels. At 1/4000 second it is 2.1 pixels. To get the smear under a single pixel at that geometry you need 1/8333 second.

Read that again with a measurement cursor in your hand. At the film-look setting, every edge on that vehicle is a gradient 139 pixels wide, roughly the width of its own headlight in the image. There is no edge to click on. The cost of fixing it is real: you lose about four stops of light, a stop meaning a doubling or halving of light, compared with a 180 degree shutter at 60 frames per second, and fast shutters produce strobing rather than smooth motion. Pay that cost on purpose and say in your report that you paid it.

22.2For any video you shoot to measure motion, set the shortest shutter the light allows, and record the shutter setting in the log at the moment you set it.

What a group of pictures actually stores

Modern video does not store pictures. It stores a group of pictures, and the Scientific Working Group on Digital Evidence defines the parts of it precisely in its Technical Overview of Digital Video Files, document 17-V-001. An intra frame, called an I frame, contains "all newly encoded information." A predicted frame, or P frame, contains "information relating to changes from the previous I-frame." A bidirectional frame, or B frame, is "encoded based on interpolation from the nearest I- and/or P-frames." Longer groups compress better and, in the working group's words, "do not capture quick transitions as effectively."

What that means in bytes is more persuasive than any definition. In a short test clip encoded with a group length of 15, the leading I frame occupies 3,683 bytes and the three frames that follow it occupy 78, 41, and 27 bytes. Nobody looking at 27 bytes believes it is an independent picture of anything. It is a set of instructions for modifying other pictures. Five things follow, and you should be able to say all five from the stand: you cannot verify a single frame in isolation, different decoders produce different pixels, damage to one predicted frame propagates until the next self-contained frame, open groups make frame extraction depend on data outside the group, and re-encoding will never reproduce the file bit for bit. The stored order is not the display order either, which the working group states directly in its Core Technical Concepts for Time-Based Analysis of Digital Video Files: "the order and timing in which frames are presented is not necessarily the same as the way the frames are stored within the multimedia container."

For video you create, use a codec that encodes every frame independently. Apple's published data rates for 1920 by 1080 at 29.97 frames per second run from 45 megabits per second for the proxy tier to 220 for ProRes 422 HQ and 495 for ProRes 4444 XQ. Storage is cheap. Explaining a predicted frame to a jury is not.

Two kinds of timecode, and how each is carried

The Society of Motion Picture and Television Engineers Standard ST 12-1:2014, Time and Control Code, defines it. Linear timecode is 80 bits per frame carried as an audio-band signal running from 960 Hz to 2400 Hz, which is why a spare audio track can hold it, and why it becomes unreadable when the transport slows or stops. Vertical interval timecode carries 90 bits, of which 32 are the time code, 32 are user data, 18 are synchronization, and 8 are a checksum, and it can be read on a paused frame.

Drop-frame timecode skips labels, not recorded frames

Distinguish drop-frame timecode from missing recorded frames. The numbering convention itself does not remove captured frames. For 30000/1001 frames per second with 30-count timecode, drop-frame numbering omits labels 0 and 1 at the start of each minute except every tenth minute, removing 108 labels per hour. At that exact recording rate, non-drop timecode reaches 01:00:00:00 after 3,603.6 seconds, while drop-frame timecode differs from elapsed time by about 3.6 milliseconds per hour. Do not apply those label counts to other rates without checking the relevant convention.

22.3When two cameras must agree, remember that genlock locks the rate and jam sync only sets the value; a jam-synced pair holds the same number and drifts apart all afternoon.

Chapter 22 Checklist: Video Fundamentals

Chapter 23The Measurements That Lie

Most bad video measurements come from bad video. This one comes from good video, correctly exposed, in focus, and wrong by a fifth.

Your sensor reads one row at a time

A rolling-shutter sensor exposes or reads different rows at different times. Motion during that interval can distort shape and position. Identify the sensor mode and timing, then evaluate the effect on the proposed measurement rather than assuming every measurement will be wrong.

Convert the subject's speed into pixels per second on the image plane, which is focal length times world speed divided by the product of pixel pitch and distance. Multiply that by the per-row delay. The result is the tangent of the angle by which every vertical edge in the frame leans away from true vertical. The object's own size cancels out of that expression, which is the elegant part and the testable part: a lamp post, a door frame, and a building corner all lean by the same angle, so any known-vertical feature in the scene lets you solve for either the readout time or the subject's speed.

Put numbers on it with the same camera geometry used in the last chapter: a 50 mm lens, 5.0 micrometer pixels, a subject at 30 meters moving at 25 meters per second, which works out to 8,333 pixels per second of image-plane motion, on a sensor 3,000 rows tall. At a readout time of 66.7 milliseconds, one fifteenth of a second, every vertical edge leans 10.49 degrees and the top of the frame is displaced 555.6 pixels from the bottom. At 33 milliseconds it is 5.29 degrees. At 6 milliseconds it is 0.96 degrees. At 3.7 milliseconds it is 0.59 degrees. On a true global shutter it is zero.

Those readout times are not guesses. Jim Kasson has published oscilloscope measurements of shutter transit made by photographing a free-running function generator on a scope with a known time base and counting the displacement between the top and bottom of the frame. His figures: 3.7 milliseconds for a stacked Nikon Z9 in electronic shutter, about 6 milliseconds for the first-generation Sony a9, about 64 milliseconds for a Nikon Z7 in silent mode, and about 71 milliseconds for a Sony a7R II in silent full-frame mode. His class statement for pre-stacked Sony camera bodies is that electronic scan times "vary from about 1/14 second to 1/30 second for a full frame image," which is 33 to 71 milliseconds. Global shutter exists but is rare and recent: Sony's Alpha 9 III product page describes a full-frame stacked 24.6 megapixel sensor with a global shutter system and a "maximum 1/80000 second shutter speed with flash sync," and that flash sync claim is the diagnostic signature.

23.1Before you measure anything off a video frame, find out whether the sensor rolled, and how fast.

The length error is bigger than the skew

Motion along the scan direction can stretch or compress a rolling-shutter image. Under the stated model, apparent height depends on image-plane speed and per-row delay. At the chapter's example geometry, a 66.7 millisecond readout yields about 23 percent elongation or 16 percent compression. Calculate the effect for the actual motion rather than treating length error as case-deciding.

A rolling-shutter error of that size would materially affect the example measurement. For the actual file, characterize readout timing and motion, account for any prior correction, and determine whether correction or an uncertainty bound supports the intended use. Error magnitude alone does not decide admissibility.

How to spot a rolling shutter in the picture

Partial-frame illumination, skew, and banding can indicate rolling-shutter behavior. Interpretation requires the illumination timing, exposure, sensor mode, and possible artifacts. A band alone does not uniquely establish readout time or whether a particular lamp was energized.

Twenty years of research, and no published standard

There is real literature here, and citing it shows the field has thought about this for twenty years. Ait-Aider, Andreff, Lavest, and Martinet showed at the 2006 European Conference on Computer Vision that a single rolling-shutter frame encodes the subject's instantaneous velocity. Hedborg, Forssén, Felsberg, and Ringaby published rolling shutter bundle adjustment at the 2012 Conference on Computer Vision and Pattern Recognition, reformulating structure from motion so that each scan line carries its own camera pose. Dai, Li, and Kneip showed in 2016 that the ordinary epipolar constraint does not hold on rolling-shutter imagery. Albl, Kukelova, Larsson, and Pajdla published rolling shutter absolute pose in the 2020 volume of the Institute of Electrical and Electronics Engineers Transactions on Pattern Analysis and Machine Intelligence. Oth, Furgale, Kneip, and Siegwart published a calibration method in 2013, which matters because the line delay is a measurable camera parameter and not an excuse.

In the research behind this book, the complete published index of the Scientific Working Group on Digital Evidence was reviewed, including every video, imaging, photography, and multimedia document. No published guidance addressing rolling shutter was identified. That is not proof that none exists anywhere, and you should say it that carefully. But it means that if you wait for a standards body to hand you a method, you will testify without one.

23.2Close the standards gap in your own report, before your opponent opens it: name the effect, state the readout time you measured or the range you could not exclude, and state the resulting bound on your measurement.

Interlaced video is two pictures pretending to be one

Interlacing is the older version of the same problem, and it is still everywhere in legacy footage. A 1080i frame is not a frame. It is two fields, odd lines and even lines, captured at different instants and composited afterward. At 59.94 fields per second the field interval is 16.683 milliseconds and the frame interval is 33.367. When the subject moves between the two field captures you get combing, the horizontal teeth on vertical edges that people mistake for compression damage.

Deinterlacing methods differ. Weaving retains both fields but can show combing in motion; bobbing interpolates missing lines; motion-adaptive methods select processing by region. Preserve the original and document processing. Choose field or frame analysis for the timing and spatial question rather than ranking every deinterlacer as destructive.

Work from the fields, not from deinterlaced frames

For analysis you want the fields, not the frames. Separating the fields of a 720 by 480 interlaced clip yields twice as many images at 720 by 240. You trade half the vertical resolution for double the temporal resolution: 59.94 time samples per second instead of 29.97, and timing quantization cut from 33.4 milliseconds to 16.7. For a speed calculation that doubles your data points. No working group guidance on field-based analysis was identified either, so present it on the engineering, and note that any reader with the free tools can reproduce the field count.

23.3Check the declared field order and the per-frame interlace flags before you assume a legacy file is progressive.

Chapter 23 Checklist: Rolling Shutter and Fields

Chapter 24High-Speed Video and Mechanism

Some events are faster than the case can see. A discharge, an impact, a fastener letting go, a rope releasing: the whole mechanism lives in a few milliseconds, and ordinary video records the before and the after with nothing in between.

High-speed video can document event sequence and support spatial or motion measurements. If a test sequence supports a causal opinion, assess the test's reliability, its relation to the event conditions, and competing explanations. Sequence alone does not establish causation.

The light requirement rises with the frame rate

The first constraint is light, and it is arithmetic rather than opinion. Exposure time shrinks in proportion to frame rate, so the light requirement rises in proportion. Relative to 60 frames per second, 500 frames per second needs 8.3 times the light, which is 3.06 stops, a stop meaning a doubling or halving of light. One thousand frames per second needs 16.7 times, or 4.06 stops. Five thousand frames per second needs 83.3 times, which is 6.38 stops. Ten thousand frames per second needs 166.7 times, 7.38 stops. That is why high-speed impact work runs continuous lighting arrays measured in tens of kilowatts. The cameras are not insensitive. There is simply no time to collect photons.

24.1: Plan lighting alongside camera, exposure, resolution, trigger, and safety requirements before the test.

The sensors compensate with enormous pixels. Photron publishes a 20 by 20 micrometer pixel pitch for the FASTCAM NOVA S20, which is roughly ten to twenty times the linear pitch of a phone sensor and one hundred to four hundred times the collecting area per pixel. That camera is specified at 18,750 frames per second at 1,024 by 1,024 in 10-bit mode, at 20,000 frames per second at 1,024 by 992, and at up to 1,100,000 frames per second at a reduced 128 by 16. Its minimum exposure is 0.2 microseconds, and Photron states that minimum is independent of frame rate, which matters more than the headline number: the frame rate sets how often you sample, and the exposure sets how sharp each sample is. Across the same product line at full 1,024 by 1,024, the S6 runs 6,400 frames per second, the S9 runs 9,000, the S12 runs 12,800, and the S16 runs 16,000. The smaller Mini AX series runs 2,000, 4,000, and 6,400 frames per second at that resolution with a shutter adjustable from 1 millisecond to 1 microsecond. The Orion S40 is specified at 31,250 frames per second at 1,280 by 1,024 with a 1.0 microsecond minimum exposure.

At the accessible end, the Chronos 2.1-HD records 1,920 by 1,080 at 1,000 frames per second on a 10 micrometer pitch sensor with a minimum shutter of 10 microseconds, at a published base price of $6,800. Kron publishes its record times: 2.7 seconds on 8 gigabytes, 5.5 seconds on 16, and 11 seconds on 32.

You get seconds of recording, not minutes

Those record times are the second constraint, and they are the one that surprises people. Work the arithmetic yourself: bytes per frame equals pixels times bit depth divided by eight, and record time equals memory divided by bytes per frame times frame rate. For the Chronos, 1,920 by 1,080 is 2.0736 megapixels, 12 bits packed is about 3.11 megabytes per frame, and 1,000 frames per second is about 3.11 gigabytes per second, so 8 gigabytes buys about 2.6 seconds. The manufacturer says 2.7. The arithmetic is honest.

You cannot press the button on a collision

You are recording for a few seconds, and you cannot press the button on a collision. These cameras run a continuously overwriting memory buffer and keep a window of frames around a trigger. The Chronos documents an End Trigger mode that "records until defined delay after trigger," which is functionally that behavior. Photron's product pages document memory segmentation rather than trigger modes. Manufacturer-documented pre-trigger percentages were not obtained in the research for this book, so specify them from the manual for the camera you rent, and put that page in your file.

24.2: Document trigger scheme, delay, and pre-event window before loading a specimen. Check them alongside lighting, framing, timing, and specimen preparation.

A reported frame rate is a setting, not a measurement

Timebase is the third constraint, and the one experts skip. A camera that reports 5,000 frames per second is reporting a setting, not a measurement. If you intend to derive a velocity or a duration from frame counts, put an independent time reference in the frame. A calibrated timing light, a strobed source of known frequency, or a free-running signal displayed on an oscilloscope in the corner of the shot all work, and all of them let you verify the interframe interval from the recording itself rather than from the menu. This is the same trick used to measure sensor readout times, and it is good engineering rather than a published standard, so present it as method and show the result.

Slow motion is more persuasive than it deserves

Slow motion can alter impressions of duration and opportunity to respond. State the real elapsed time and distinguish slowed analysis from a claim about what an actor could perceive or do.

No decision addressing slow motion as an independent ground for exclusion surfaced in the research behind this book, and I will not pretend otherwise. But the objection has two doctrinal homes and both are live. Under Federal Rule of Evidence 403 the concern is that the exhibit misleads. Under Fusco v. General Motors Corp., 11 F.3d 259 (1st Cir. 1993), the operative question is whether a demonstration is "sufficiently close in appearance to the original accident to create the risk of misunderstanding by the jury," and slowing an event by a factor of 150 changes appearance more than any lens choice ever will.

Label capture and playback rates, state real elapsed time, and explain why slow playback assists the analysis. Where useful, provide real-time playback as a comparison. Disclosure helps interpretation but does not alone resolve misleading presentation.

24.3Label every high-speed exhibit with capture rate, playback rate, and true elapsed time, on the image, not in a footnote.

Keep every take, including the misfires

High-speed footage is enormous, and it will tempt you to keep only the good takes. Keep everything, including the misfires and the frames before the trigger, because a partial production of a test series is a spoliation argument waiting to be made. And remember that a high-speed clip is a test result. Chapter 27 governs it, and the substantial similarity of your test setup to the real event is a foundation you must lay, not an objection you get to answer later.

Chapter 24 Checklist: High-Speed Capture

Chapter 25Surveillance Video: Get the Native File

Prefer native surveillance exports and preserve the player and timing information needed to interpret them. Copies vary: a bit-for-bit copy preserves data, while transcoding or screen capture can introduce changes. Assess the actual transfer history and proposed measurement.

Native export first, and the player with it

Take the first road. The Scientific Working Group on Digital Evidence, in its Best Practices for Data Acquisition from Digital Video Recorders, document 17-V-002, prefers a native or proprietary export because it is "likely to provide best evidence for legal authenticity purposes as it is closest to the original manner of recording," and it requires that you also take the viewer application and codec from the device itself. The working group does not publish a formal ranked list, so do not tell a court it did. The preference order is implied by the document's structure, and it runs from native export, to an open-format export taken as a secondary backup because it "should also be acquired if time is available," to network export, to a memory stick export, to optical media on older units, to a hardware capture device, to imaging the drive directly, to seizing the whole unit.

A disk image, native export, transcoded export, and screen recording preserve different information. Determine what the actual system retains, including timestamps, settings, logs, codec data, and deleted material. Preserve configuration screens separately and compare exports before relying on timing or geometry. Do not assume every export path has the same losses.

A screen recording documents a player's display and may retain useful scene information. It also adds display and capture limitations, so obtain the native recording where possible and assess each proposed use separately.

25.1Ask for the native file in writing, in the first letter, and quote the working group's preference language in the request.

Verify the nominal frame rate

Confusing 29.97 with 30 frames per second costs you one tenth of one percent.

Surveillance timing can vary with recorder configuration, resource limits, and motion triggers. SWGDE gives an example changing from 5 to 15 frames per second. Determine timing from the actual recording and system rather than assuming either a constant or variable rate. Preserve relevant timestamps and settings.

In the constructed test file, the nominal rate is 10 frames per second, the average is 6.45, and one interval is 1.2 seconds. Treating that interval as 0.1 seconds makes a distance-over-time speed twelve times the true value, an overstatement of 1,100 percent. This illustrates a timing risk, not the error in every surveillance file.

The constructed example shows why nominal frame rate can fail to represent a particular interval. Use the timestamps or other validated timing evidence for the frames being measured. The example's error ratio does not establish how large errors are in other recordings.

25.2For every measurement interval, use the actual elapsed time between the two specific frames you used. Never use frame count divided by nominal rate.

That failure mode is worth naming for its own sake, because it is the shape of most confident wrong answers in this field: a respected source, followed faithfully, on a tool that changed underneath it, producing silence that looks like agreement.

How to test a file for a variable rate

Work from the native file in the manufacturer's player. Extract per-frame presentation timestamps. Compute the difference between consecutive timestamps rather than an average rate. Tabulate or plot those differences, because the irregularity becomes obvious to a juror the moment it is drawn. Two independent checks tell you whether the file is variable in the first place: the container's nominal rate compared against its average rate, where a mismatch is the primary indicator, and the dedicated variable-frame-rate detector filter in the FFmpeg tools, which reports the fraction of intervals departing from the mode along with the minimum, maximum, and average frame duration. Only a zero result with matching minimum and maximum is a clean answer of constant rate. Where the container has no reliable timing at all, which is common in proprietary formats, establish timing empirically by recording an event of known duration through the same unit at the same settings, or by reading the recorder's own burned-in timestamps, and document which you did.

Capture the clock offset before you leave

Measure the recorder's clock offset at collection against a verified reference and record the sign, time zone, and reference. Do not change the recorder's time or date. A collection-time offset does not by itself establish the offset at the incident if the clock drifted, reset, or was adjusted.

Legacy surveillance pixels are not square

Verify sample aspect ratio in legacy surveillance footage. A 720 by 480 recording intended for 4:3 display requires an 8:9 sample ratio; displaying those samples as square makes it about 11.1 percent too wide. Other intended display ratios require different treatment. Apply the verified geometry to the measurement.

25.3: Inspect encoder tags as clues to processing history. A general-purpose media-library tag alone does not establish whether a recorder or later software wrote the export.

25.4Collect a margin of time on both sides of the incident, not just the incident window, because you will want the idle-period frame rate to compare against.

Chapter 25 Checklist: Surveillance Video Collection

Chapter 26Recording the Witness

Poor interview audio can leave words unrecoverable. Monitor the recording and address noise, placement, and level before the interview proceeds.

Choosing the microphone, and getting it close

Microphone construction affects sensitivity, response, power needs, and handling. Select a microphone for the room and source, then test placement through headphones. Close placement helps direct-to-room sound ratio but is not the only determinant of intelligibility.

Pattern follows construction. A capsule open only at the front is omnidirectional. One open front and back responds to the pressure gradient and is directional, which brings proximity effect, meaning bass boost as you approach, and heightened sensitivity to wind and handling noise. An omnidirectional capsule brings neither.

Published distance factors compare directional patterns under stated sound-field assumptions. A value near 2 for a hypercardioid indicates twice the reference distance for the specified direct-to-reverberant ratio; it does not describe every benefit or limitation of that microphone.

26.1: Place the microphone close enough for clear speech, then check noise, placement, level, and room reflections through headphones.

For an ideal point source in a stable reverberant field, reducing distance from 60 to 15 centimeters increases direct level by about 12 decibels. Test the actual recording setup; microphone pattern, room treatment, and noise control also affect intelligibility.

Which is why the shotgun microphone is usually the wrong tool indoors. An interference tube cancels off-axis sound by path-length difference, and cancellation requires that difference to be a meaningful fraction of a wavelength. At 200 Hz a wavelength is 1.7 meters, and a short tube cancels nothing. Published measurements of a modern shotgun show a directivity index flat at 6 decibels from 63 Hz through 1 kHz, which is what a plain hypercardioid delivers, and a small room's reverberant energy lives in exactly that region. Outdoors the shotgun is the right tool. In an office it is a boom pole holding a hypercardioid.

Placement has a documented cost too. The microphone manufacturer DPA publishes measurements showing that for chest and neck placement, "the range between 2-4 kHz is practically removed from the sound spectrum, which results in poor speech intelligibility." That band carries the consonants. When a chest-mounted lavalier transcript is peppered with "inaudible," whether that reflects the speaker or the microphone is a real technical question with a real answer.

Choose the cluttered office over the glass conference room

Choose the recording room by listening and testing. Reverberation, noise, distance, and microphone placement affect intelligibility. A small furnished room can help, but room labels alone do not establish performance.

26.2Aim the directional microphone's null at the noise source, not just its front at the witness.

Where to set levels, and what format to record

Aim dialogue peaks at 12 to 6 decibels below full scale and keep margin for unexpected levels. EBU R 128 and ATSC A/85 provide delivery loudness targets, not recording levels. Use uncompressed 48 kilohertz, 24-bit recording for this workflow and monitor for clipping and noise. Bit depth does not eliminate level-setting risk.

26.3Record on two independent devices, with separate power and separate media. Not two tracks on one recorder.

Federal law is a floor, not a ceiling

Now the law, and the answer is that this is counsel's question and not yours. Title 18 of the United States Code, Section 2511(2)(d), provides that it "shall not be unlawful under this chapter" for a person not acting under color of law to intercept a communication "where such person is a party to the communication." Federal law is a floor, not a ceiling. It disclaims illegality only "under this chapter," and it never displaces a state statute.

A minority of states require the consent of all parties, and that minority is more complicated than any list will tell you. California, Florida, Maryland, Pennsylvania, and Washington are solid all-party jurisdictions reaching both in-person and telephone conversations. Massachusetts, Illinois, and Montana prohibit secret, surreptitious, or hidden-device recording rather than requiring consent, so open announced recording is lawful in all three even over objection. Connecticut's all-party rule is civil only and telephone only. Nevada requires all-party consent by telephone and one-party consent in person. Michigan's statute is ambiguous as to participants and the offense is a felony. Delaware has two statutes in conflict, and Vermont has no wiretapping statute at all.

Do not rely on that paragraph. It is a summary, it will drift, and it is not legal advice. Confirm the rule with retaining counsel, in writing, for every jurisdiction the conversation touches, before the interview.

Oregon, and the vacated opinion still in circulation

Oregon deserves its own correction, because most sources still report a holding that no longer exists. Oregon Revised Statutes Section 165.540 splits: telephone communications require one participant's consent, while an in-person conversation may not be obtained if "not all participants in the conversation are specifically informed that their conversation is being obtained." That is notice, not consent. On July 3, 2023, a Ninth Circuit panel held the in-person provision facially unconstitutional. On March 19, 2024, the court granted rehearing en banc and stated that "the three-judge panel opinion is vacated." On January 7, 2025, the en banc court affirmed dismissal, holding the statute content-neutral and concluding that it survives intermediate scrutiny. Project Veritas v. Schmidt, No. 22-35271 (9th Cir. Jan. 7, 2025) (en banc). Any text telling you the Ninth Circuit struck that statute down is describing a vacated opinion.

When the conversation crosses a state line

Across state lines there is no uniform rule. California's Supreme Court has applied a comparative impairment analysis to hold that California law governed calls recorded from another state into California, in Kearney v. Salomon Smith Barney, Inc., 39 Cal. 4th 95 (2006). Confirm the current citation and holding with retaining counsel before you rely on it.

In Becker v. Computer Sciences Corp., 541 F. Supp. 694 (S.D. Tex. 1982), a court applying the most-significant-relationship test reached the opposite result on similar facts. Washington's statute reaches communications "between points within or without the state" by its own terms.

Apply the most restrictive rule among every jurisdiction the call touches, and ask the witness where he physically is. Area codes prove nothing.

Announce the recording on the recording

Announce the recording on the recording. Your name, the date, the statement that you are recording, the question whether you have permission, and the answer. That satisfies every all-party statute surveyed, satisfies the notice-only statutes, defeats the secret and surreptitious elements in Massachusetts, Illinois, and Montana, and creates its own proof.

Ask counsel one more question before you press record: whether to record at all. A recording is a document, and whether it is discoverable is a legal question with consequences. What you do with the resulting statement belongs to a different book in this series, Being a Great Expert Witness. This one stops at the file.

Chapter 26 Checklist: Recording the Witness

Chapter 27Testing, Reenactment, and Substantially Similar Conditions

Documenting a scene and staging an event are different jobs with different rules. Experts get in trouble when they do the second while believing they are doing the first.

Documentation records a condition that already exists. Testing creates a condition and records what happens. The moment you build, load, drop, or drive something for the camera, you have entered a doctrine with its own foundational burden, and that burden falls on you before the exhibit is admitted rather than on your opponent afterward.

Substantial similarity is your burden, not theirs

The best-written statement of it is Fusco v. General Motors Corp., 11 F.3d 259 (1st Cir. 1993). Judge Boudin conceded the power of the exhibit at the outset: the test track footage was "vivid and pertinent." Then he explained why courts distrust it. The concern "lies not with use of tape or film" but "with the deliberate recreation of an event under staged conditions," because "jurors may be misled because they do not fully appreciate how variations in the surrounding conditions, as between the original occurrence and the staged event, can alter the outcome." From that the court drew the rule this chapter is built on, describing it as a doctrine predating and now loosely appended to Federal Rule of Evidence 403, one "that requires a foundational showing of substantial similarity in circumstances."

First, similarity is your affirmative burden. Second, and this is the point most experts miss, the label you attach does not control. General Motors argued the footage illustrated general scientific principles rather than recreating the accident. The court's answer: "the critical point is not one of labels. The issue for us is whether the demonstration is sufficiently close in appearance to the original accident to create the risk of misunderstanding by the jury."

Sufficiently close in appearance. That is a photographic test written into evidence law. Focal length, camera height, framing, and lighting all change appearance without changing a single physical fact, which is why every craft chapter in this book has a home here.

27.1Decide before you shoot whether the exhibit is illustrative or experimental, write that decision down, and then build the shoot to match the answer.

Illustrative or experimental, and the foundation each owes

The decision matters because it changes the foundation you owe. Four Corners Helicopters, Inc. v. Turbomeca, S.A., 979 F.2d 1434 (10th Cir. 1992) states the whole structure in four consecutive paragraphs. Where imagery is illustrative, "admissibility of experimental evidence does not depend on identical actual and experimental conditions" and "typically, dissimilarities go to the weight of the evidence rather than its admissibility." Where it purports to simulate the event, experiments "may be admissible if made under conditions which are substantially similar," and while "the conditions need not be identical, they must be sufficiently similar to provide a fair comparison." Then the two sentences to tape above your desk: "if the evidence is offered to merely show physical principles, the experiment should be conducted without suggesting that it simulates actual events," and "it is important then that the jury be instructed that the evidence is admitted for a limited purpose only."

Four Corners affirmed exclusion on the grounds described in that decision. For another exhibit, identify the intended purpose and support it with the actual setup and presentation. A label alone neither establishes nor defeats admissibility.

How close is close enough, case by case

Gladhill v. General Motors Corp., 743 F.2d 1049 (4th Cir. 1984) shows what mismatch costs. The accident happened at night, on a downhill grade, at a sharp curve. The braking demonstration was conducted "on a flat, straight, asphalt surface in daylight by an experienced test driver." The Fourth Circuit reversed and directed that "evidence of this test should be excluded entirely on retrial," observing that "it is elementary physics that automobiles traveling downhill with their front wheels turned do not behave the same way with their brakes locked as those traveling on a flat surface with their front wheels straight." Four variables were mismatched: illumination, grade, curvature, and driver expectancy. Two are photographic conditions and two are physical. Courts do not separate them.

The doctrinal language across circuits is consistent enough to quote. Jackson v. Fletcher, 647 F.2d 1020 (10th Cir. 1981), where a test truck weighed 37,000 pounds less than the real one, states the purpose plainly: "the object of the rule which requires substantial similarity of conditions is to prevent admission of evidence which tends to mislead and perhaps confuse the jury." Barnes v. General Motors Corp., 547 F.2d 275 (5th Cir. 1977) and Hall both require conditions "so nearly the same in substantial particulars as to afford a fair comparison." Sanchez v. Denver & Rio Grande Western Railroad Co., 538 F.2d 304 (10th Cir. 1976) adds that where motion pictures "purport to represent a reenactment of human conduct the court should scrutinize the foundation with great care as to detail."

The other side of the ledger is where your exhibit lives if you build it correctly. In Randall v. Warnaco, Inc., 677 F.2d 1226 (8th Cir. 1982), a videotaped experiment came in, the court noting that "admissibility does not depend on perfect identity between actual and experimental conditions." In Bannister v. Town of Noble, 812 F.2d 1265 (10th Cir. 1987), the tape came in for a limited purpose under an instruction worth copying into your own proposed language: "The film is not being introduced for the purpose of attempting to recreate the accident involved in this case. ... The film is introduced only to demonstrate certain physical principles."

27.2If your exhibit is illustrative, draft the limiting instruction yourself and hand it to retaining counsel with the exhibit.

Evaluate authentication separately from Rule 403

A second, independent route of attack lives in Federal Rule of Evidence 901 rather than Rule 403. United States v. Stearns, 550 F.2d 1167 (9th Cir. 1977) holds that "a photograph may be distorted, and thus inadmissible as a technically inaccurate representation of the scene photographed." Under Rule 403 your opponent must show that probative value is substantially outweighed. Under Rule 901 you must produce evidence sufficient to support a finding that the image is what you claim it is. Claim an image shows what the driver saw, and if your focal length compressed or expanded apparent distance, it is not what you claimed. That is the stronger objection, and the one to make against the other side's exhibit.

Document the setup as carefully as the result

Document the setup as thoroughly as the result. The model comes from the losing side in Four Corners, where the opposing expert catalogued the dissimilarities one variable at a time: a high-torque lathe against a low-torque engine, roughly 1,000 revolutions per minute against 35,500, all of the torque applied to the screw against a small fraction, a test running 45 to 54 seconds against an event lasting under two seconds, and no support behind the screw head and therefore no wedging. Quantified, variable by variable. That is the affidavit that killed the exhibit, and it is the affidavit you should write about your own test first.

27.3Photograph the rig before the test, during the test, and after the test, and photograph the instrument settings and the specimen identification in the same frames.

27.4Keep every take, including the ones that did not work, and produce them.

Give notice before a test destroys the article

Before a test that will alter an article, have counsel resolve notice, inspection, and protocol requirements. Preserve the condition record and document attendance or objections. Notice does not by itself resolve preservation or admissibility issues.

Chapter 27 Checklist: Testing and Reenactment

Part Five. The Chain

Chapter 28The Testimony Inside the File

A photograph is a picture with a statement attached to the back, written by the camera, in a language nobody in the courtroom reads.

That statement is the image metadata: a block of structured text the camera writes at capture, recording what made the file, when, with what lens, at what settings, and sometimes where. It has a name, the Exchangeable Image File Format, and one fact about it surprises people: it is a camera industry standard published by a Japanese trade association, not an international standard. The companion framework, the Extensible Metadata Platform, is the one with an international designation.

Which fields can carry an opinion

Most of the block is device housekeeping. A handful of fields are load-bearing, meaning a timeline or an opinion can rest on them. Read those first and quote them in the report.

Start with time, because there are three time fields and experts confuse them constantly. DateTimeOriginal records when the scene was captured, at shutter release. DateTimeDigitized records when the data was written as digital data, the same instant in a native digital camera and a different one for a scanned film frame. DateTime records when the file was last changed, and editors update it on save. A modification date later than the capture date proves nothing. A modification date three weeks later, sitting beside a Software field naming an image editor, is a reason to ask the next question.

Make and Model name the camera body. Software records the name and version of the program or firmware that generated the image, the fastest tell that a file passed through an editor. BodySerialNumber ties the file to a specific instrument rather than a model, and LensModel and LensSerialNumber do the same for the optic. Then the exposure record: exposure time, aperture, the sensitivity field the standard now calls PhotographicSensitivity and older cameras label ISOSpeedRatings, and two focal length fields, one actual and one giving the equivalent on a 35 millimeter film camera.

28.1Read the metadata of every file you receive before you form an opinion from it, and put the reading in your file.

Verify the camera clock

Identify how the camera obtains and maintains time, including any synchronization features. Compare it with a verified reference during the session and record the offset. Do not infer the body's accuracy from a specification for a separate clock component.

Check whether the file contains a time-zone offset. Offset fields entered the EXIF format in version 2.31, but implementations vary. A local timestamp without an offset or independent context does not uniquely identify an absolute capture time.

At the start of every session, photograph a known-accurate time display, a satellite receiver readout or a network-synchronized clock, in or immediately beside your first evidence frame. Repeat at the end. The capture time of that frame, compared against the time pictured in it, gives a signed offset, and bracketing the session gives drift across it, so you can state a bound rather than a point estimate. Write down the body and serial number, the reference, the time it showed, the time the camera recorded, the offset, and the zone you were standing in.

28.2Establish the clock offset by photographing a known time reference at both ends of every session, and record it in writing the same day.

Then do not correct the originals. Read-only first, always: examine with a tool running in read mode, hash the file before and after, and show the values match. If a correction is warranted, apply it to working copies and report it as a documented correction with the original values preserved. Rewriting timestamps on an original destroys the record you were retained to keep.

What the location block proves about your clock

Location metadata may include a separate UTC time reference. Establish how and when the device generated those fields before comparing them with camera time. A seven-hour-and-four-second difference could reflect a zone setting and drift, but it does not alone prove that explanation or rule out editing.

Before relying on a coordinate, read the processing method field, which records whether the fix came from satellites, a cell tower identifier, or a wireless network database. A wireless or cell-derived fix is a positioning inference that can be wrong by hundreds of meters, and its time is not satellite-derived. Read the horizontal positioning error field too, the closest thing to an uncertainty bar the format offers. The published figures for the global positioning system are commitments about the signal and the constellation, not about the receiver in your pocket: a worst case pseudorange accuracy of 7.8 meters at a 95 percent confidence level, and horizontal error of 8 meters or better 95 percent of the time as a global average, with the caveat that actual accuracy depends on atmospheric effects, sky blockage, and receiver quality. An expert who testifies that location tagging is accurate to five meters has quoted a system specification as a device result.

It cuts at you as well. Your geotags disclose where you stood, when, and which way you faced. A request for all photographs from the site inspection can sweep in your rental car, your hotel, and an unrelated matter shot with the same body that afternoon. Decide the policy before the inspection, and never strip coordinates from an original afterward, because stripping metadata from an original is a spoliation problem.

28.3Decide whether location tagging is on or off before the inspection, and never change an original to match a decision you made later.

How ordinary handling strips the metadata out

Now the uncomfortable part, because it is about your workflow rather than somebody else's. Metadata dies from ordinary handling, and every path below is one experts use weekly. Email an image and the client, the server, or a resizer in between may rebuild it from decoded pixels, starting from an empty metadata block. Text it and the platform re-encodes and downscales. Download it from a social platform and presume the embedded metadata is gone: periodic testing by the photo metadata working group at the Embedded Metadata Initiative has repeatedly found that leading platforms display no embedded metadata and strip most of it from retrievable files. Those rounds are roughly a decade old; say so when you cite them. There is no verified public data on the major messaging applications, so do not testify about them from memory.

Cloud libraries and document applications may preserve originals, create derivatives, or strip metadata depending on the operation and settings. A screenshot is a new rendering, not a file copy of the depicted image. Inspect the actual output and transfer path rather than assuming a universal result.

Missing metadata can result from capture settings, transfer, processing, or deliberate removal. The absence alone does not identify the path or establish tampering.

The exchange to rehearse before you testify

When asked about capture time, distinguish the recorded timestamp from a verified time. Explain the reference, measured offset, preserved originals, and supporting log, and state any limits. Those records support the timeline; they do not determine the verdict.

28.4Never offer a metadata timestamp as a fact without stating how the clock was verified and what the offset was.

Chapter 28 Checklist: The File's Own Testimony

Chapter 29Chain of Custody for Files

Track custody of both physical media and the associated files.

The formulation is not mine. The National Institute of Justice's courtroom guide to digital evidence, catalog number 211314, states it plainly: two chains of custody are involved, the physical item itself and its associated data, and the issues regarding the data are additional to those regarding the item. The memory card is one chain. The file is a second, parallel chain, because a file can be altered without anyone touching the card it came from.

What a hash does, and what it does not

The instrument that holds the second chain together is a hash. A hash function takes a file of any size, runs every bit of it through a fixed procedure, and produces a number of fixed length written as a string of characters. Run it on a 40 megabyte raw file and you get the same length of output as from a one-line text file. Change one bit anywhere, one pixel or one character in one metadata field, and the output changes completely and unpredictably.

It is not encryption; you cannot recover the file from it. It is a fingerprint.

The tools are free and already installed on every operating system you own. For a folder of evidence, hashdeep hashes a whole directory tree, writes the values to a known-value file, and later audits the tree against it and reports every discrepancy. That audit is what you run four years from now, and it is why you build the list today.

Collision resistance is not preimage resistance

Which algorithm to use has become a deposition fight, and the fight rests on a misunderstanding worth getting exactly right. Hash functions resist two different attacks. Collision resistance asks whether an attacker can find two files, both of his own choosing, producing the same hash. Preimage resistance asks a different question: given a hash you already recorded, can an attacker construct a different file producing that same value. The National Institute of Standards and Technology quantified both in Special Publication 800-107, since withdrawn, and the asymmetry is the point and survives the withdrawal. Collision resistance strength in bits is half the output length; preimage resistance strength equals the full output length. SHA-1 produces 160 bits, so its collision strength was never above 80 bits while its preimage strength is 160. MD5, the older Message Digest algorithm, has never been an approved algorithm at all.

The published attacks are real, and know them by name because your opponent may. Collisions in MD5 were demonstrated in 2004. Collisions in SHA-1 were demonstrated on February 23, 2017 by a Dutch national research institute working with Google, at a cost of about 6,500 processor-years and 110 graphics-processor-years. In January 2020 a French and Singaporean team demonstrated a chosen-prefix collision for about $75,000, using roughly 900 consumer graphics cards for two months.

Every one of those is a collision attack. In every one, the attacker chose both files. That is not your situation.

Evidence integrity rests on preimage resistance and nothing else. You hashed a file at acquisition and wrote the value into your log. The question a court cares about is whether somebody could later build a different file matching that value. No published attack does this against any of these algorithms. The Scientific Working Group on Digital Evidence, the live standards body in this field, published a position on exactly this question on September 29, 2019, and two of its sentences belong in your file. It is appropriate to use both MD5 and SHA-1 for integrity verification, the working group wrote, provided the hash is securely stored or recorded in the examination documentation. And: since there are no preimage attacks on any of the four hashing algorithms discussed, the only way to manipulate the evidence without detection is to do it before it is hashed.

Record the hash contemporaneously and protect that record independently. A hash computed today establishes a baseline for future comparisons; it does not by itself prove the file's earlier history or show that no changes occurred after the calculation without a later comparison.

29.1Record the acquisition hash the day you acquire the file, in a document stored separately from the file.

None of that is a reason to keep using the old algorithms. The institute has announced a transition away from the Secure Hash Algorithm 1, written SHA-1, for all applications by December 31, 2030. Use the 256-bit member of that family, SHA-256, as your primary. The working group's best practice for digital evidence acquisition, revised March 3, 2025, directs hashing before and after a copy and again before storage. Two algorithms cost one extra command.

29.2: Use SHA-256 for integrity checks and document any second algorithm used. Preserve the values and verification results independently of the files.

The original, the working copy, and the line between them

The primary image is the first instance in which an image is recorded onto media that is a separate identifiable object, meaning what is on the card. The original image is an accurate and complete replica of it. A working copy is anything you process, and the moment you process it, it becomes derivative evidence carrying its own integrity requirements. The working group's guidance on maintaining the integrity of imagery, current as of March 3, 2025, sets the sequence: images are stored in an unaltered state, review and processing are completed on a copy, and hashing is performed before and after any copy operation and again before storage.

Write protection is the mechanical half of the same idea, and here most photographers are wrong. The sliding tab on the side of a memory card does not write-protect anything. The card's circuitry does not detect the switch position; the tab is a flag the host is expected to honor voluntarily, and some devices ignore it. If write protection matters you need a hardware write blocker, which does not depend on anyone's good behavior. The federal tool testing program publishes a specification whose first requirement states the point: a hardware write blocker shall not, after receiving an operation of any category from the host nor at any time during its operation, transmit any modifying category operation to a protected storage device.

Copy the card before you do anything else to it

Card handling is the same discipline one step earlier. Copy, do not move: the card is the only copy until a hash-verified duplicate exists elsewhere, and only then does it get wiped for reuse. Do not review and delete frames in camera, because deleting mid-shoot fragments the card, breaks the sequential file numbering that is itself corroborating metadata, and destroys the only copy of a frame you cannot assess on a three-inch screen. Prefer several small cards to one large one. If the camera body has two slots, set them to write simultaneously rather than to overflow. Format cards in the camera that will use them, not on a computer.

29.3Never format a card until a hash-verified copy exists on two separate devices, and log the verification before you format.

What your custody log has to record

The log ties it together, and it is unglamorous on purpose. Federal guidance on integrating forensic techniques describes a defensible one: a record of every person who had physical custody, the actions they performed and at what time, secure storage when the item is not in use, examination performed only on a copy, and verification of both original and copy. The law enforcement examination guide adds the standard for your notes: detailed enough to allow complete duplication of your actions, with dates, times, results, and the irregularities you hit and what you did about them. One page per case does it.

A duplicate comes in without a hash, so hash it anyway

Rules 1001 and 1003 address duplicates. Hash comparisons support a claim of bit-for-bit identity but are not a prerequisite to every admission route. Authentication, fairness concerns about using a duplicate, and other evidentiary requirements remain for counsel and the court.

29.4Keep one custody page per case, in ink, listing every access, copy, and process by date, and treat it as an exhibit from the day you open it.

Chapter 29 Checklist: The Second Chain

Chapter 30Storage That Outlives the Case

Preservation failures can prevent later examination or production of an image. Retain verified copies and document any loss and its effect.

Storage is where careful imaging goes to die, and it dies quietly. The failure surfaces at the worst moment: a supplemental production request in a case that went dormant for three years and then woke up.

The three-two-one rule has a citation problem

The rule everyone recites is the three-two-one rule: keep at least three copies of the data, on at least two different types of storage media, with at least one copy offsite. It is good advice with a provenance problem, and I say so plainly because conceding is a credibility move. The rule is commonly attributed to a federal computer emergency readiness publication on data backup options, and separately to the photographer Peter Krogh and his digital asset management work from 2005. Neither attribution could be verified in the research behind this book, and the federal cybersecurity agency's current ransomware guidance does not use the label at all. It says to maintain offline, encrypted backups and test their integrity.

Redundant copies reduce dependence on a single device when their failure risks are sufficiently independent. The cited dataset's 2025 annualized failure rate does not predict a particular drive's lifetime. State the failure-rate and dependence assumptions used in any multi-year calculation, and account for shared risks such as deletion, theft, or account compromise.

30.1Keep three copies on two kinds of media with one offsite, and justify the rule from failure rates, not from a citation.

The national archives will not take your raw file

The National Archives and Records Administration publishes tables of formats it accepts for permanent electronic records, updated August 2025. For born-digital photographs the preferred format is the Tagged Image File Format, versions 4, 5, and 6, and nothing else. Acceptable formats include the JPEG File Interchange Format, Adobe's Digital Negative version 1.6.0.0, Portable Network Graphics version 1.2, and JPEG 2000 Part 1. Proprietary camera raw files do not appear at all. The national archives will not take your camera's native raw file. The Library of Congress, in its Recommended Formats Statement for 2025 to 2026, puts Digital Negative and proprietary camera raw in the same acceptable tier, so Digital Negative's advantage is real at the archives and nonexistent at the Library.

Retain the camera original and an uncompressed archival master in a documented format. Test both periodically and plan migration when software or media support changes.

30.2: Archive the camera original and a documented preservation master, and verify both remain readable.

Bit rot is measured, not folklore

Treat a manufacturer's unrecoverable-read-error specification as a bound under stated conditions, not an observed failure rate. It does not justify predicting a fixed error count on a particular archive read or calling an error statistically likely without further assumptions. Verify stored data with checksums and independent copies.

The best published study observed 1.53 million disk drives over 41 months and found more than 400,000 checksum mismatches: 0.86 percent of nearline drives developed them against 0.065 percent of enterprise drives. The finding that should change your architecture is that 8 percent of the corruptions discovered were discovered during rebuild. The moment an array reconstructs itself after one failure is the moment the second problem finds you.

A redundant array of independent disks protects against a device dying. It does not protect against deletion, ransomware, overwriting, or your own mistake, and without block checksums it cannot tell a good copy from a corrupted one. Redundancy is availability. It is not backup. The defense is a file system that checksums every block plus a scheduled pass, called a scrub, that reads all the data and repairs what it can from a replica. The documentation for the checksumming file systems in common use recommends a scrub period of a month or less, and they ship weekly and monthly timers.

How long each medium lasts sitting unpowered

Media lifetimes are where the marketing is worst and the federal guidance is best. The institute's 2022 publication on digital evidence preservation gives expected longevity for unused media, meaning shelf life sitting unpowered. A pre-recorded optical disc: under 10 years, not recommended. A recordable compact disc or digital versatile disc: under 30 years. Blu-ray: under 30 years. Tape: 20 years. A hard disk drive: under 2 years, not recommended for archival. A solid state drive: under 1 year, not recommended.

Read those last two again. The semiconductor standards body specifies powered-off retention of one year at 30 degrees Celsius for client-class solid state drives and three months at 40 degrees for enterprise drives, and those minimums worsen with temperature. An external drive in a desk drawer is not an archive. It is a copy with an expiration date nobody wrote on the label.

The one optical medium the federal guidance rates for the long term is the inorganic-layer disc sold as M-DISC, at 100 years or more. Its marketing claims a thousand years, which the same manufacturer contradicts in other markets by advertising a hundred years or more, so do not print the thousand. The supporting evidence is accelerated aging, not observed longevity, and it is contested: a 2009 Naval Air Warfare Center report run on behalf of the technology found the organic-dye comparison brands failing the aging series, while later French national metrology laboratory testing rated the same disc under 250 hours at 90 degrees Celsius. Cite the federal number.

Write-once media earns its place for what it does to testimony. A recordable optical disc is write-once by construction, the cheapest true write-once medium available to a solo expert and the one most intelligible to a jury. In the cloud, an object lock in compliance mode cannot be overwritten or deleted by any user, including the account root user, until its retention date passes. Write-once turns "I did not alter the file" from testimony into a property of the system. It also protects only the copy you locked and does not prove the file was correct when you wrote it.

30.3Put at least one copy on media that cannot be rewritten, and be ready to say why that beats your own logbook.

The archive workflow a solo expert can keep up

Ingest by copying, never moving, and hash everything with SHA-256 before and after the copy. Designate the original and never touch it again. Work only on copies. Package the case as a bag with a checksum manifest. Distribute that bag three ways: a working drive running a checksumming file system, a cloud object store with versioning and an object lock, and an offline copy on a different medium kept somewhere other than your office. Then verify on a schedule you can keep: scrub monthly, revalidate the manifest quarterly, restore the offsite copy once a year. Log each verification. Once built, it takes about two hours a year.

30.4Test a restore from the offsite copy once a year and log the result, because an unverified backup is a belief, not a copy.

How long you keep it is not a technical question

How long must you keep case imagery? I found no standard, no rule, and no government publication prescribing a retention period for an expert witness, and I will not invent one. That is a legal and professional responsibility question, not a technical one. It turns on your engagement agreement, the statute of limitations and the statute of repose for the underlying claim, any protective order or litigation hold, and your carrier's requirements. Those push toward longer than you expect. Get the number from retaining counsel and from your carrier, in writing, per engagement, and write it into the case manifest.

Chapter 30 Checklist: The Archive

Chapter 31Authentication

Authentication is not a finding that your photograph is true. It is a finding that a jury could reasonably decide it is what you say it is.

Federal Rule of Evidence 901(a) provides: "To satisfy the requirement of authenticating or identifying an item of evidence, the proponent must produce evidence sufficient to support a finding that the item is what the proponent claims it is."

Read the operative words. Evidence sufficient to support a finding. Not proof, not certainty, not a certificate. As Lorraine v. Markel American Insurance Co., 241 F.R.D. 534 (D. Md. 2007), put it, a court need not find that the evidence is necessarily what the proponent claims, only that a jury might.

The three illustrations that carry imagery

Rule 901(b) then gives a list, introduced as examples only and not a complete list. Three of them carry imagery. Rule 901(b)(1), testimony of a witness with knowledge, is one line: "Testimony that an item is what it is claimed to be." Rule 901(b)(4), distinctive characteristics and the like: "The appearance, contents, substance, internal patterns, or other distinctive characteristics of the item, taken together with all the circumstances." Rule 901(b)(9), evidence about a process or system: "Evidence describing a process or system and showing that it produces an accurate result."

The Advisory Committee Note to that ninth example says it is designed for situations in which the accuracy of a result is dependent upon a process or system which produces it, and offers X-rays as a familiar instance. Hold that comparison. Nobody saw the inside of the bone; the image comes in because the machine works.

All of this reaches video and digital stills through Rule 1001(c): a photograph "means a photographic image or its equivalent stored in any form." Medium-agnostic on its face, which is why raw files, recorder containers, and frame grabs are all governed by the photograph rules.

31.1Learn Rule 901(a) as a sentence you can recite, because everything else here is an application of it.

Pictorial testimony against the silent witness

Two theories carry imagery into evidence. The first is the pictorial testimony theory, sometimes called the illustrative theory. The photograph is not independent evidence; it is a nonverbal way of expressing a witness's testimony. In United States v. Rembert, 863 F.2d 1023 (D.C. Cir. 1988), the court stated the foundation directly: a sponsoring witness, whether or not he is the photographer, who has personal knowledge of the scene depicted testifies that the photograph fairly and accurately portrays that scene. He need not know anything about the camera and need not have been present when the image was made. Rembert also declined to confine the rule to the two named models, noting that the uses of photography have not stood still and neither should the law.

The second is the silent witness theory. The image is itself substantive evidence of what it portrays, independent of any person who perceived the event, and the foundation comes entirely from the imaging system. In Bergner v. State, 397 N.E.2d 1012 (Ind. Ct. App. 1979), the Indiana Court of Appeals described the photograph as speaking for itself, with no need for a witness to testify that it accurately represents what he or she observed, and required evidence as to how and when the camera was loaded, how frequently it was activated, when the photographs were taken, and the chain of custody of the film.

Personal observation can support pictorial testimony, while process evidence can support recordings without an observing witness. Surveillance footage may also be authenticated through a knowledgeable witness or circumstantial evidence. Select a foundation for the actual exhibit rather than assigning routes solely by camera type.

United States v. Taylor, 530 F.2d 639 (5th Cir. 1976), is the foundational federal silent witness decision. A bank camera was activated only after employees were locked in the vault, so no teller could testify that the film accurately depicted what they saw. The foundation accepted was testimony about how the film was installed, how the camera was activated, that the film was removed immediately after the robbery, the chain of its possession, and that it was properly developed. Process testimony, nothing else, and it sufficed.

United States v. Stearns, 550 F.2d 1167 (9th Cir. 1977), adds the other half: the contents of a photograph itself, together with such other circumstantial evidence as bears upon the issue, may serve to explain and authenticate it. Stearns also opens with the sentence every imaging expert should memorize: a photograph may be distorted, and thus inadmissible as a technically inaccurate representation of the scene photographed. Distortion is an authentication problem, which is the doctrinal home of every lens question in Chapter 8. A competent opponent attacks foundation rigor, not the theory, and that is where he starts.

31.2: Identify and prepare the authentication evidence appropriate to each exhibit before testimony.

The self-authenticating shortcut added in 2017

Since December 1, 2017 there has been a shortcut, and it is the part most often stated backwards. Rule 902(13) makes self-authenticating "a record generated by an electronic process or system that produces an accurate result, as shown by a certification of a qualified person that complies with the certification requirements of Rule 902(11) or (12)," with the proponent also required to meet the notice requirements of Rule 902(11). Rule 902(14) makes self-authenticating "data copied from an electronic device, storage medium, or file, if authenticated by a process of digital identification, as shown by a certification of a qualified person that complies with the certification requirements of Rule 902(11) or (12)," again with the notice requirement.

Paragraph (13) is the self-authenticating analogue of Rule 901(b)(9), the process route. Paragraph (14) is the analogue of Rule 901(b)(4) applied to bit-for-bit copies. Neither displaces Rule 901. Each avoids the cost of a live witness for something nobody contests.

The Advisory Committee Note to paragraph (14) explains the mechanism. Data copied from electronic devices, storage media, and electronic files, it says, are ordinarily authenticated by hash value, a number produced by an algorithm based upon the digital contents of a drive, medium, or file. If the hash values for the original and copy are different, the copy is not identical to the original. If they are the same, it is highly improbable that they are not identical, and identical hash values reliably attest that they are exact duplicates. The amendment allows self-authentication by a certification of a qualified person that she checked the hash value of the proffered item and that it was identical to the original.

Now the limiting sentence in the same Note, which keeps this from becoming a trap: "The rule is flexible enough to allow certifications through processes other than comparison of hash value, including by other reliable means of identification provided by future technology."

That forecloses the strong reading. Rule 902(14) makes hash matching a sufficient shortcut. It does not make hashing a prerequisite to admission. A proponent who never computed a hash may still authenticate under 901(b)(1), 901(b)(4), or 901(b)(9), and no decision I have found requires a hash, a write blocker, or a working-copy protocol as a condition of admitting a photograph. The National Institute of Justice's courtroom guide to digital evidence, catalog number 211314, does not discuss hash values at all, and reports that courts have generally not been receptive to alteration claims absent specific evidence of alteration. Two more sentences close it out: a certification can only establish that the item is authentic, and the opponent remains free to object on other grounds.

31.3Hash and certify because it removes an argument cheaply, not because the rule requires it, and never testify that hashing is required.

Two gaps to concede before the other side finds them

First, authenticating a photograph does not authenticate the container it was found in: Griffin v. State, decided by Maryland's high court on April 28, 2011, held that pages printed from a social media profile were not properly authenticated, because someone other than the purported creator could have made them. Second, the case law has not caught up to the hardware. The framework plainly extends to dashboard cameras, body-worn cameras, and drone footage, but I know of no decision squarely so holding. Say that as analysis, not authority.

What the rules ask, and what they do not

The rules do not ask whether your photograph is beautiful, or expensive, or made with the equipment somebody in the courtroom happens to own. They ask whether you can produce evidence sufficient to support a finding that the file is what you say it is. Every habit in Part Five exists to make that answer boring.

31.4Prepare the authentication foundation for every exhibit before you write the report, not the night before the deposition.

Chapter 31 Checklist: Foundation

Chapter 32Detecting the Faked and Defending the Real

An error-level-analysis display shows differences in recompression response. It does not, by itself, establish deliberate manipulation. Evaluate the method's assumptions and limitations before drawing a conclusion.

The technique is error level analysis, and the mechanism explains in one breath. The tool takes your JPEG, the compressed format most cameras produce by default, resaves it at a chosen quality to introduce a known error everywhere, subtracts the resave from the input, and amplifies what is left. Because JPEG quantizes each 8 by 8 block of pixels independently, an untouched file should respond uniformly. In the developer's words, "If the image is completely unmodified, then all 8x8 squares should have similar error potentials." Bright regions are read as content that went through fewer compression cycles, which is to say, as content pasted in later.

Now read the same author's own limitations, on the same page as the tutorial. "[Error level analysis] only identifies what regions have different compression levels. It does not identify sources." If a file has been resaved enough times, "the [error level analysis] will return a black image and no modifications can be identified using this algorithm." And the sentence that should end the practice: "With Photoshop, the simple act of saving the picture can auto-sharpen textures and edges, creating a higher error level potential. This artifact does not identify intentional modification; it identifies that an Adobe product was used." The site's own frequently asked questions add that "There is a difference between real and authentic. A real photo of a forged document or a staged situation will not appear unusual," and that the site itself "does not draw any conclusions" and works "like a microscope."

There is a second problem, and it is a citable absence. The Scientific Working Group on Digital Evidence, the live body whose documents govern this field, published version 2.0 of its best practices for image authentication on March 3, 2025. Error level analysis is not in it at all.

Then there is the record in public. In May 2013 an analyst published a claim that the World Press Photo of the Year was a significantly reworked digital composite, resting on error level analysis, a shadow argument, and a reading of the file's metadata. The organization retained two independent examiners, who reported on May 14, 2013: "It is clear that the published photo was retouched with respect to both global and local color and tone. Beyond this, however, we find no evidence of significant photo manipulation or compositing." They added that "the analysis purporting photo manipulation is deeply flawed." The photographer had developed one raw file at different densities to balance uneven light in an alleyway, which is the digital equivalent of dodging a print. That is the technique's most public outing.

32.1Do not put error level analysis in your report. When an opponent puts it in his, read his own tool's documentation into the record before you say a word about photographs.

What the honest techniques can and cannot show

Assess authentication methods within their tested conditions. The cited JPEG-ghost and sensor-fingerprint studies report performance for particular datasets and attack scenarios. Compression, cropping, region size, processing, and adversarial manipulation can affect transfer to case imagery. Report the relevant validation rather than treating study figures as universal thresholds.

Copy-move analysis addresses duplication within an image, not every form of compositing. Color-filter-array methods can degrade under compression, as the cited study illustrates. Identify the actual file and processing before applying those results; do not assume all evidence is JPEG.

The working group states the limit better than I can. "The state of the art in digital imagery is such that in a single image, manipulations can be performed which a trained forensic practitioner may not adequately detect." Authentication "should be performed on a series of images depicting the same or similar subjects, or on video." And: "Results should not be reported in terms of numerical probability without a proper scientific foundation and/or related research."

32.2: Do not treat a single algorithm as conclusive authentication. Report numerical confidence only with a proper scientific foundation applicable to the method and data.

What a signed manifest binds to your pixels

Provenance is the industry's answer, and it is a real advance. The content provenance specification behind what is marketed as Content Credentials binds three things into a signed manifest: assertions, which are structured statements about the file such as capture metadata, actions taken, and hashes; a claim, which is a signed wrapper referencing those assertions; and the signature itself, carried in a certificate chain and timestamped by an independent authority. The binding to the pixels is a cryptographic hash over byte ranges of the file, using the Secure Hash Algorithm at 256, 384, or 512 bits. Cameras ship it: the Leica M11-P was first in the world, on October 26, 2023, Sony launched signing across several camera bodies on June 26, 2025, and the first consumer phone arrived in August 2025.

Documented failures of camera-signing systems

Now the history, because it is the part that keeps this honest. In November 2010 a security firm defeated Canon's Original Data Security Kit by dumping the camera's memory, extracting the embedded secret keys, and computing the value responsible for detecting modification. In April 2011 the same firm defeated Nikon's Image Authentication System, which hashed metadata and image data separately with the Secure Hash Algorithm at 160 bits and signed the results with a 1024-bit key stored in a maker note tag. The finding was blunt: "The private (should-be-secret) cryptographic key is handled inappropriately, and can be extracted from camera." Nine models were affected.

Fourteen years later, on September 5, 2025, Nikon suspended its content credentials service on the Z6III. The reason was not cryptography. The camera's multiple exposure mode would combine signed photographs with unsigned photographs into one output file and then sign the result. Genuine credentials, attached to imagery that was never authenticated.

A device that signs autonomously must hold the key, and a key inside a device anybody can buy is a key an adversary can buy. A signing pipeline can also be induced to sign the wrong thing. Provenance proves an origin claim, not truth.

32.3Treat a content credential as evidence of where a file came from, never as evidence that the scene was real.

Check detector performance beyond its training data

Artificial intelligence generated imagery is where practitioners most want a tool and least have one. The National Institute of Standards and Technology addressed it in its November 2024 report on reducing the risks posed by synthetic content. Detectors do not generalize: they perform better on images from the generator they were trained on, and cross-generator accuracy runs 50 to 70 percent, which at the low end is a coin flip. Watermarking is not a fix either. Researchers have "theoretically proven and empirically confirmed" that for any conceivable image watermarking scheme the mark can be removed by adding noise and then denoising, and most current schemes "have been consistently found vulnerable to removal." Overall: "none of these techniques offer comprehensive solutions on their own."

Combine provenance records with technical examination

Authentication can draw on witness knowledge, circumstantial evidence, process records, and technical examination. Preserve raw files, contemporaneous hashes, time references, originals, and processing records. Those practices support the foundation but do not make laboratory analysis irrelevant or exhaust Rule 901's routes.

Chapter 32 Checklist: Authentication and Fakery

Chapter 33What You Must Turn Over

Preserve the full image set and have counsel determine disclosure obligations. Images considered in forming testimony may be discoverable even if omitted from the report. Consulting roles, protections, and court orders can affect the analysis.

Start with the text, because the text is where the argument lives. Federal Rule of Civil Procedure 26(a)(2)(B) requires that an expert disclosure "must be accompanied by a written report," one "prepared and signed by the witness," from a witness "retained or specially employed to provide expert testimony in the case." The report must contain "(i) a complete statement of all opinions the witness will express and the basis and reasons for them; (ii) the facts or data considered by the witness in forming them; (iii) any exhibits that will be used to summarize or support them," and then qualifications with a ten-year publication list, a four-year list of prior testimony, and "a statement of the compensation to be paid for the study and testimony in the case."

Subparagraphs (ii) and (iii) are the whole imaging question. Subparagraph (iii) is the easy half: your photo boards, overlays, animations, and scan renderings are exhibits that will summarize or support your opinions, and they go over. Subparagraph (ii) is the half that catches people.

Considered is a wider net than relied upon

Are your photographs "facts or data considered by the witness"? Work it through rather than guessing. The 2010 Advisory Committee Note to Rule 26 says the refocus onto "facts or data" was meant "to limit the disclosure requirement to material of a factual nature by excluding theories or mental impressions of counsel." Then it says the opposite of what an expert hopes: "At the same time, the intention is that 'facts or data' be interpreted broadly to require disclosure of any material considered by the expert, from whatever source, that contains factual ingredients. The disclosure obligation extends to any facts or data 'considered' by the expert in forming the opinions to be expressed, not only those relied upon by the expert."

Read the last clause twice. Considered, not relied upon. A photograph of the accident site contains factual ingredients by definition; that is the entire reason you took it. If you shot two hundred and six frames at a site inspection, looked at all two hundred and six on the rear screen of the camera or on your screen, and kept six for the report, you considered two hundred and six. The six you kept are relied upon. The two hundred you set aside are still considered.

33.1: Preserve every frame and treat it as potentially discoverable; have counsel determine the actual disclosure obligation.

What the draft protection covers, and where it stops

Federal Rule of Civil Procedure 26(b)(4)(B) provides that "Rules 26(b)(3)(A) and (B) protect drafts of any report or disclosure required under Rule 26(a)(2), regardless of the form in which the draft is recorded." That is broad in one direction and narrow in another. Broad, because form does not matter: a draft is protected whether it is written, electronic, or otherwise, and the protection reaches drafts of supplementation too. Narrow, because it protects drafts of a report or disclosure. That and no more.

The Committee said where the shield stops, and it said it in language written for exactly this problem. "Rules 26(b)(4)(B) and (C) do not impede discovery about the opinions to be offered by the expert or the development, foundation, or basis of those opinions. For example, the expert's testing of material involved in litigation, and notes of any such testing, would not be exempted from discovery by this rule." And even where a party makes a showing of substantial need, the protection for mental impressions "does not extend to the expert's own development of the opinions to be presented; those are subject to probing in deposition or at trial."

Site photographs are not drafts of a report. Test photographs are not drafts of a report. Point clouds are not drafts of a report. They are the testing and the notes of the testing, which the Note names as unprotected. There is one closer question, and you should concede it before you are pushed: a preliminary version of an animation built to be embedded in the report may well be a draft of a Rule 26(a)(2)(B)(iii) disclosure. The site photographs from which that animation was built plainly are not.

Three carve-outs in the attorney communication shield

Federal Rule of Civil Procedure 26(b)(4)(C) protects communications between the party's attorney and a reporting expert, "regardless of the form of the communications," with three carve-outs. Communications are discoverable to the extent they "relate to compensation for the expert's study or testimony," "identify facts or data that the party's attorney provided and that the expert considered in forming the opinions to be expressed," or "identify assumptions that the party's attorney provided and that the expert relied on in forming the opinions to be expressed."

That middle exception is an imaging exception more often than lawyers realize. When counsel emails you six scene photographs taken by an adjuster, that email identifies facts or data the attorney provided and you considered. The strategy discussion around it is protected. The photographs, and the fact that they came from counsel, are not.

33.2Log the provenance of every image in your file: who made it, when you received it, and from whom. You will be asked, and "counsel sent it" is not an adequate answer eighteen months later.

The consulting role, and who pays for production

Rule 26(b)(4)(D) shields the non-testifying consultant: ordinarily a party "may not, by interrogatories or deposition, discover facts known or opinions held by an expert who has been retained or specially employed by another party in anticipation of litigation or to prepare for trial and who is not expected to be called as a witness at trial," absent exceptional circumstances. If your role is truly consulting, that is a different posture, and it is counsel's call, not yours. Rule 26(b)(4)(E) says the party seeking discovery must pay you "a reasonable fee for time spent in responding to discovery" unless manifest injustice would result. Producing three hundred raw files and a photograph log is compensable time. Say so in your engagement agreement before it happens.

Preserve frames omitted from the report

Deleting a frame does not resolve whether it was considered in forming an opinion or subject to preservation. Retain originals and have counsel assess the actual disclosure obligation. Select report images without destroying the rest of the set.

33.3Cull by selecting, never by deleting. Move frames out of the report, not out of the file.

Unlitigated is not the same as settled

The research for this book located no decision squarely addressing the particular expert-photograph question. That is a search limit, not proof that the issue is unlitigated. Apply Rule 26 and current authority with counsel to the expert's role and use of the images.

Shoot as if every frame will be an exhibit, because it may be. Not the frame you love. The frame you nearly did not take, the one with your own shadow in the corner, the one where the flash misfired. Somebody will get all of them, and the only question you control is whether they are a set you are proud of or a set you have to explain.

Chapter 33 Checklist: Disclosure

Chapter 34Spoliation and the Deleted Frame

Deleting an image can create preservation and disclosure problems. Preserve the full set and document any accidental loss.

What Federal Rule of Civil Procedure 37(e) actually asks of you

Federal Rule of Civil Procedure 37(e) governs, and it is short enough to hold in your head. "If electronically stored information that should have been preserved in the anticipation or conduct of litigation is lost because a party failed to take reasonable steps to preserve it, and it cannot be restored or replaced through additional discovery, the court: (1) upon finding prejudice to another party from loss of the information, may order measures no greater than necessary to cure the prejudice; or (2) only upon finding that the party acted with the intent to deprive another party of the information's use in the litigation may: (A) presume that the lost information was unfavorable to the party; (B) instruct the jury that it may or must presume the information was unfavorable to the party; or (C) dismiss the action or enter a default judgment."

Three features of that text run this chapter. It reaches electronically stored information, which your image files, raw files, and video exports plainly are. It asks whether reasonable steps were taken, not whether the outcome was perfect. And it splits remedies at intent.

The 2015 Advisory Committee Note tells you where the duty comes from. "Rule 37(e) is based on this common-law duty; it does not attempt to create a new duty to preserve. The rule does not apply when information is lost before a duty to preserve arises." The Note adds a warning aimed at judges that experts should read as a small mercy: "It is important not to be blinded to this reality by hindsight arising from familiarity with an action as it is actually filed."

On the standard itself, the Note is generous. "Due to the ever-increasing volume of electronically stored information and the multitude of devices that generate such information, perfection in preserving all relevant electronically stored information is often impossible." And: "This rule recognizes that 'reasonable steps' to preserve suffice; it does not call for perfection."

Routine, good-faith operation of an electronic information system is a relevant factor, "although the prospect of litigation may call for reasonable steps to preserve information by intervening in that routine operation."

Three places the routine deletion keeps running after your duty attaches

Intervening in that routine operation is your job. It has three faces.

The first is the memory card. Reformatting between jobs is a good habit that becomes a bad one the moment a duty attaches. My rule is that a card is not reformatted until the files are copied, hashed, and confirmed present in two locations, and that a card carrying imagery in a matter where litigation is anticipated is not reused until counsel says so.

34.1Never reformat a card until the offload has been hashed and verified in two locations, and never at the scene.

Review cloud retention, trash, synchronization, and storage-optimization settings for every account holding evidence. Determine whether each setting deletes originals, removes local copies, or preserves recoverable versions. Disable or supplement settings that conflict with the hold, and record the changes.

34.2Disable every automatic deletion, purge, and optimize-storage setting on any device or account that touches evidence, and record the date you did it.

The third is the hold letter. When counsel issues a litigation hold, most experts read it as instructions to the client. It reaches you. Your cards, working drives, offsite copies, synced accounts, and email attachments are all within its scope if they hold matter-related imagery. I will not quote you the sentence about litigation holds that every article on this subject repeats, because it comes from two district court opinions whose full text I could not verify in a published reporter. An expert who quotes an opinion he has not read is one question from a bad afternoon. What follows is verified: the rule, the 2015 Note, and one case.

The duty reaches evidence you inspected but never owned

That case is Silvestri v. General Motors Corp., 271 F.3d 583 (4th Cir. 2001), and it belongs in every expert's file. A driver struck a utility pole and the airbag did not deploy. His experts "inspected and photographed the vehicle and inspected the site, and each prepared a report of his findings." The vehicle then went to an insurer, to a repair shop, and out into the world. General Motors was not told about the accident for almost three years.

The court defined the wrong: "Spoliation refers to the destruction or material alteration of evidence or to the failure to preserve property for another's use as evidence in pending or reasonably foreseeable litigation." The duty "arises not only during litigation but also extends to that period before the litigation when a party reasonably should know that the evidence may be relevant to anticipated litigation." And it stated the obligation that reaches nearly every expert, because you rarely own the thing you examine: "If a party cannot fulfill this duty to preserve because he does not own or control the evidence, he still has an obligation to give the opposing party notice of access to the evidence or of the possible destruction of the evidence if the party anticipates litigation involving that evidence."

The photographs did not save the case. The court said the opposite: "To require General Motors to rely on the evidence collected by Silvestri's experts in lieu of what it could have collected would result in irreparable prejudice." Dismissal affirmed.

The expert's photographic record was excellent, and its excellence proved the party knew the vehicle mattered, examined it, and let it go without telling anyone. Thorough documentation is not a defense to spoliation. It can be the evidence of spoliation.

34.3When you inspect something you do not control, tell counsel in writing the same day that the item exists, where it is, and that it is at risk.

Cull by selection, never by deletion

Culling is not the problem. Culling silently is the problem.

Culling as a discipline means you shoot everything, preserve everything, and then select. The report carries six frames. The file carries two hundred and six. Your log states which frames were selected and why, and the unselected frames are produced with the rest. The selection becomes a demonstration of method.

Deleting frames can create a preservation issue when a duty applies. Notify counsel, investigate whether files can be restored or replaced, and document the loss and recovery steps. Rule 37(e) requires assessment of its conditions rather than a presumption that every deletion satisfies them.

Rule 37(e)(2) does raise the bar for the severe sanctions. The Note is explicit that the rule "rejects cases such as Residential Funding Corp. v. DeGeorge Financial Corp., 306 F.3d 99 (2d Cir. 2002), that authorize the giving of adverse-inference instructions on a finding of negligence or gross negligence," because "[n]egligent or even grossly negligent behavior does not logically support that inference." Do not read that as comfort. The Note preserves a path under subdivision (e)(1) needing no intent finding at all: a court may allow "the parties to present evidence to the jury concerning the loss and likely relevance of information." Loss without bad intent is not costless.

Rule 37(e) "applies only to electronically stored information." A lost print, negative, or slide falls outside it and back onto the court's inherent authority and the common law, which is where Silvestri operates.

Research limits on deleted expert imagery

I have found no authority applying any of this to an expert's own deleted frames, raw files, or point clouds. That is a real gap, and I state the conclusion as inference: the rule is medium-agnostic on its face, nothing in it exempts an expert's working files, and Silvestri shows the duty attaching to material an expert generated. The 2015 Note treats "a party's own information-retention protocols" as a relevant independent obligation, which cuts both ways. Better to have one and follow it than to improvise under oath.

34.4: Use a written retention protocol, supplemented for each matter's holds and orders. Do not reduce preservation because a case is going badly.

Chapter 34 Checklist: Preservation

Chapter 35Where You May Point the Camera

A camera confers no right of entry. Every place you want to photograph belongs to somebody, and the question is never whether you can get the angle. It is whose permission the angle requires, and in what form.

The rule that lists photograph among the things you may do

The ordinary vehicle is Federal Rule of Civil Procedure 34(a)(2), which lets a party serve a request "to permit entry onto designated land or other property possessed or controlled by the responding party, so that the requesting party may inspect, measure, survey, photograph, test, or sample the property or any designated object or operation on it." Read the verb list. "Photograph" is expressly enumerated, so photography on a Rule 34 inspection needs no separate authority. Note also "possessed or controlled": control is the touchstone, not ownership.

Rule 34 reaches only parties. For everyone else, Rule 34(c) builds the bridge: "As provided in Rule 45, a nonparty may be compelled to produce documents and tangible things or to permit an inspection." Rule 45(a)(1)(A)(iii) lets a subpoena command a person to "permit the inspection of premises," and Rule 45(d)(2)(A), captioned "Appearance Not Required," provides that such a person "need not appear in person at the place of production or inspection unless also commanded to appear for a deposition, hearing, or trial." That power dates to the 1991 amendments, not the 2013 ones.

Why an inspection is harder to win than documents

Getting an inspection ordered is harder than getting documents. The framework is relevance and proportionality under Rule 26(b)(1), overlaid with the balancing stated in Belcher v. Bassett Furniture Industries, Inc., 588 F.2d 904 (4th Cir. 1978): "Since entry upon a party's premises may entail greater burdens and risks than mere production of documents, a greater inquiry into the necessity for inspection would seem warranted," and "the degree to which the proposed inspection will aid in the search for truth must be balanced against the burdens and dangers created by the inspection." The order there let plaintiffs' expert roam five plants over five days and question employees without designated areas of inquiry. Reversed as improvidently granted. On the other side, New York State Association for Retarded Children, Inc. v. Carey, 706 F.2d 956 (2d Cir. 1983), affirmed an inspection expressly permitting experts to photograph conditions.

35.1Write the photography terms into the inspection stipulation yourself. Counsel negotiates access; only you know what you need to shoot.

Courts condition rather than deny, and Rule 26(c)(1) supplies the menu: terms of time, place, and expense, limits on scope, and, in subparagraph (E), "designating the persons who may be present while the discovery is conducted." A workable protocol fixes the duration, the areas in scope, the attendees, one designated photographer with an equipment list, what may and may not be imaged, and a bar on talking to the owner's employees. In Belcher, unsworn on-site questioning of employees was a principal ground for reversal, because it functions as an unrecorded deposition with none of the protections.

Confirm authority before entering an adjoining parcel

Private property outside a discovery order runs on consent and trespass law. In the general common-law formulation, trespass is complete on intentional entry and liability does not depend on harm, so the expert who steps twenty feet onto a neighboring parcel for a cleaner angle has likely committed a tort even though nothing was touched. The elements vary by state, and the forum state's are the ones that control. There is no news-gathering escape hatch: Branzburg v. Hayes, 408 U.S. 665 (1972), holds that "newsmen have no constitutional right of access to the scenes of crime or disaster when the general public is excluded." And access obtained by concealment is fragile. In Food Lion, Inc. v. Capital Cities/ABC, Inc., 194 F.3d 505 (4th Cir. 1999), trespass liability was affirmed not because of the misrepresentation used to get through the door, but because of the wrongful acts committed after entry: "consent to enter is vitiated by a wrongful act that exceeds and abuses the privilege of entry." Read that distinction carefully, because most summaries get it backward.

35.2Never enter a parcel you were not granted, and never obtain access by concealing who retained you.

Getting a camera into a prison or a hospital

Custodial facilities run on equal access, not on any right to walk in with a camera. Pell v. Procunier, 417 U.S. 817 (1974), holds that "newsmen have no constitutional right of access to prisons or their inmates beyond that afforded the general public," and Houchins v. KQED, Inc., 438 U.S. 1 (1978), refused to compel a television station's entry to photograph jail conditions. Federal Bureau of Prisons media regulations, at title 28 of the Code of Federal Regulations, part 540, subpart E, give an inmate "the right not to be photographed and not to have his or her voice recorded by the media" and require a media representative "to obtain written permission from an inmate before photographing or recording the voice of an inmate." Read the qualifier. Those provisions govern news media, and a retained civil expert is not a media representative. Your route is a stipulation, a Rule 34(a)(2) request, a Rule 45 subpoena, or special arrangement with the warden's approval, each of which comes with an escort and equipment pre-approval.

A private hospital is private property, and entry turns on facility policy and owner consent. The federal medical privacy law, the Health Insurance Portability and Accountability Act, binds the provider and not the visitor, but the provider carries the enforcement risk and therefore enforces categorical no-photography rules. A New York hospital entered a two million two hundred thousand dollar resolution effective April 19, 2016 after a film crew was given access. Get two consents, facility and patient. Photograph the physical environment only, keep patients and staff out of frame, and get a protective order over the images.

What the criminal rule everyone cites does not reach

Now the courthouse, where I see competent people make the most avoidable mistake. Clear away the rule everyone cites. Federal Rule of Criminal Procedure 53 bars photographing in the courtroom during judicial proceedings and broadcasting from the courtroom. It is a criminal rule, and it does not by its own force govern civil proceedings, hallways, lobbies, or the building exterior. Those are governed by Judicial Conference policy, local rules, and federal property regulations, and it is those, not Rule 53, that stop you at the door.

Judicial Conference policy, in the Guide to Judiciary Policy, volume 10, chapter 4, last revised September 18, 2023, "does not allow either civil or criminal courtroom proceedings in the district courts to be broadcast, televised, recorded, or photographed for the purpose of public dissemination." A judge may nonetheless authorize camera or recording use "for the presentation of evidence; for the perpetuation of the record of the proceedings; for security purposes; for other purposes of judicial administration; for the photographing, recording, or broadcasting of appellate arguments; or consistent with pilot programs." The prohibition dates to 1972.

"For the presentation of evidence" is your hook, and it is the answer for the expert who wants to carry a laptop, projector, tablet, or camera into a federal courtroom. It is not self-executing. It is a request, and the vehicle is a pretrial order naming the equipment and the purpose.

Local rules are the trap, because several districts bar the device from the building, not merely from the courtroom. The joint local civil rule of the Southern and Eastern Districts of New York, effective January 2, 2025, provides that no one other than court officials on court business shall "bring any camera, transmitter, receiver, recording device, cellular telephone, computer or other electronic device into any courthouse." Read that again. Not the courtroom. The courthouse. The Northern District of Ohio prohibits photography, recording, and broadcasting "in the Court House" and authorizes officers "to seize and inspect devices." The District of Maryland permits devices after screening but requires them off in the courtroom. Three districts, three answers, none in the Federal Rules.

35.3Check the local rule and standing order for the specific courthouse, by name, before every appearance. Assume nothing from the district next door.

Photographing a federal lobby counts as a commercial purpose

One more provision catches experts working premises cases in federal buildings. Title 41 of the Code of Federal Regulations, section 102-74.420, provides that except where security rules or a federal court order or rule prohibit it, persons on federal property may photograph space occupied by a tenant agency "for non-commercial purposes only with the permission of the occupying agency concerned," such space "for commercial purposes only with written permission of an authorized official of the occupying agency concerned," and "building entrances, lobbies, foyers, corridors, or auditoriums for news purposes." An expert documenting the lobby floor of a federal building in a slip-and-fall case is photographing for commercial purposes. Written agency permission, on top of any court rule.

35.4Get written permission from the occupying agency before photographing inside a federal building, and carry the paper with you.

State courts vary too much to summarize, and Chandler v. Florida, 449 U.S. 560 (1981), only tells you a state may permit camera coverage, which is not your right to bring one. Never plan an exhibit around equipment you have not confirmed you may carry through the door.

Chapter 35 Checklist: Access and Permission

Part Six. The Verdict

Chapter 36Rule 403 and the Photograph That Wins the Battle

An effective image still requires a defined evidentiary purpose and review for unfair prejudice or confusion.

Apply Rule 403 to the proposed use

Federal Rule of Evidence 403 provides: "The court may exclude relevant evidence if its probative value is substantially outweighed by a danger of one or more of the following: unfair prejudice, confusing the issues, misleading the jury, undue delay, wasting time, or needlessly presenting cumulative evidence." That text was enacted in 1975 and restyled in 2011, the Committee Note stating that the changes were "intended to be stylistic only."

Rule 403 requires the specified dangers to substantially outweigh probative value before exclusion under that rule. Apply the balance to the actual purpose and presentation. An exclusion ruling does not establish that the question was easy or the exhibit lacked value.

Authentication and relevance do not end the admissibility inquiry. Under Rule 403, the court also considers unfair prejudice, confusion, misleading presentation, and the other specified risks. An accurate image can still be excluded for its proposed use.

Assess injury imagery in context

Start with gruesome injury imagery in a civil case, where the law is more permissive than most experts expect. In Jenkins v. Associated Transport, Inc., 330 F.2d 706 (6th Cir. 1964), a civil wrongful death and personal injury case, colored photographs of the injured plaintiff's condition were admitted and the admission was affirmed. The court warned in the same breath that it "would not condone, nor should a trial judge, the use of lurid photographs, paraphernalia, or other trappings of showmanship to enhance a plaintiff's verdict," and then held that proper trial conduct was not offended. Two details are worth carrying: the sponsoring witness was the treating physician, not the photographer, and uncertainty about the exact dates the photographs were taken was not fatal because the doctor identified them as fair representations of the plaintiff's condition.

The Jenkins ruling does not create a categorical rule admitting gruesome images and excluding everything characterized as showmanship. Evaluate the image's purpose, foundation, presentation, and risks under the applicable rules.

Why the stills came in and the video stayed out

The sharpest lesson in this area comes from a single opinion that split the difference between two media. In Thomas v. C.G. Tate Construction Co., 465 F. Supp. 566 (D.S.C. 1979), the plaintiff offered a 27 minute audio and video recording of burn treatment: bandage removal, whirlpool therapy, rebandaging, with visible expressions and contortions of pain, groaning, and statements on the soundtrack. The court excluded it, finding "that the probative value is substantially outweighed and over-shadowed by the danger of unfair prejudice," and relying on the recording's "dominating effect" that "will distract the jury from its proper consideration of other issues." Then the court admitted 19 still photographs of the same injuries, reasoning that stills lack the dramatic, dominating effect of moving video.

Same injury. Same plaintiff. Same day. One medium in, one medium out.

36.1When the injury is severe, produce the still photographs first and treat moving video as a separate, harder decision that counsel makes with a written record of why.

The four concerns a day-in-the-life film has to survive

Day-in-the-life films sit at the center of this fight and the federal authority runs in both directions. In Bannister v. Town of Noble, Oklahoma, 812 F.2d 1265 (10th Cir. 1987), the Tenth Circuit affirmed admission of a videotape showing the plaintiff getting around school, entering his car, pumping gasoline, and doing tasks at home. The court acknowledged that "such films purport to show how an injury has affected the daily routine of its victim" and are often wanted because films "illustrate, better than words, the impact the injury had had on the plaintiff's life," while stating plainly that admission "raises obvious dangers of prejudice to the opposing party." The standard of review is abuse of discretion, which is why both admissions and exclusions get affirmed.

The Tenth Circuit gathered four concerns, and they are your build specification whether you are making the film or attacking one. Accuracy and fairness of foundation, drawn from Sanchez v. Denver & Rio Grande Western Railroad Co., 538 F.2d 304 (10th Cir. 1976), which held that motion pictures "must be premised by a foundation of accuracy and fairness" and that where they purport to represent a reenactment of human conduct "the court should scrutinize the foundation with great care as to detail." Self-serving behavior, because a plaintiff who knows he is being recorded for litigation is "likely to cause self-serving behavior, consciously or otherwise." The dominating nature of film. And the loss of cross-examination, because a film cannot be questioned.

That last concern produced the strongest federal appellate authority on the subject, and it is a reversal. In Foster v. Crawford Shipping Co., 496 F.2d 788 (3d Cir. 1974), plaintiff's counsel took a videotape crew to an incompetent plaintiff's home on the evening of the second trial day, without notice to the court or opposing counsel, and recorded a two minute segment showing the man "in an apparently uncommunicative and partially catatonic state, responding to interrogation with grunts and growls." The Third Circuit held that "the ruling admitting the videotape was error," and that any benefit to the factfinding process "was far outweighed by the prejudice of admitting what amounted to ex parte testimony from the absent incompetent." Reversed, new trial on damages.

Bolstridge v. Central Maine Power Co., 621 F. Supp. 1202 (D. Me. 1985), excluded a day-in-the-life tape as cumulative, because the plaintiff could testify and demonstrate her activities in open court, and added the editing problem in a sentence you should keep: "Almost always an edited tape necessarily raises issues as to every sequence portrayed of whether the event shown is fairly representational of fact, after the editing process." The formulation both Bolstridge and Bannister carry forward came from Haley v. Byers Transportation Co., 414 S.W.2d 777 (Mo. 1967), where six reels of film showing home rehabilitation were excluded because "the very obvious impact of these films would have been to create a sympathy for the plaintiff out of proportion to the real relevancy of the evidence."

There is also a sequencing safeguard that experts almost never think about because it is a trial management decision, not an imaging decision. The district court in Grimes v. Employers Mutual Liability Insurance Co. of Wisconsin, 73 F.R.D. 607 (D. Alaska 1977), admitted a day-in-the-life motion picture. The opinion itself is hard to obtain, so this account comes from the later courts that quote it, and those courts emphasized that liability had been established before the jury saw the film, so the film could not prejudice the defendant on liability. The Thomas court read Grimes that way expressly and said it doubted the Grimes court would have reached the same result with liability still open.

Offer the image that makes the point, not the flinch

When two images support the same point, compare their detail, context, and risk of unfair prejudice. Prefer the less inflammatory image if it communicates the necessary information equally well. The court's ruling and any appeal depend on the actual record.

36.2Where two accurate images prove the same fact, offer the restrained one and keep the other in the file, produced and available.

36.3Never let volume do the work of proof. Rule 403 names "needlessly presenting cumulative evidence" for a reason, and forty photographs of one wound is the reason.

Explain the actual basis for image selection, including relevant detail, measurements, context, and unnecessary graphic content. Preserve the full set and identify the selected frames. Do not claim that restraint alone eliminates other grounds for challenge.

Run the same rule against the other side's exhibits

The rule cuts the other way too, and you should be able to run it in both directions. When the other side offers an image whose only work is emotional, your report should say what fact it proves, what the less prejudicial version would have been, and what live testimony already covers the same ground. That is the Bolstridge argument, the Thomas argument, and the Haley argument in one paragraph, and it is far more persuasive than an objection that the picture is upsetting.

Chapter 36 Checklist: The Restrained Exhibit

Chapter 37Illustrative Aids Under Rule 107

Federal Rule of Evidence 107 now addresses presentations offered as illustrative aids rather than evidence. Determine each exhibit's intended use; the rule does not simply rename every item previously called demonstrative evidence.

What the rule says, and when it took effect

Federal Rule of Evidence 107 took effect December 1, 2024. It is the newest material in this book, it is the least likely thing on your shelf to be reflected in the treatise you learned from, and any chapter, checklist, or expert report written from pre-2024 sources is out of date on this point. Learn it now, because the first time you are asked about it under oath will not be the time to work it out.

The rule has four subsections. Subsection (a), on permitted uses, provides that "the court may allow a party to present an illustrative aid to help the trier of fact understand the evidence or argument if the aid's utility in assisting comprehension is not substantially outweighed by the danger of unfair prejudice, confusing the issues, misleading the jury, undue delay, or wasting time." Subsection (b), on use in jury deliberations, provides that "an illustrative aid is not evidence and must not be provided to the jury during deliberations unless: (1) all parties consent; or (2) the court, for good cause, orders otherwise." Subsection (c), on the record, provides that "when practicable, an illustrative aid used at trial must be entered into the record." Subsection (d) routes summaries of voluminous materials admitted as evidence to Federal Rule of Evidence 1006.

Notice that the balance in (a) is not the Rule 403 balance. It weighs the aid's utility in assisting comprehension, not its probative value, against the same list of dangers. Your exhibit is being judged on whether it helps the jury understand, and that is a different question from whether it proves anything.

The 2024 Committee Note supplies the definition: "An illustrative aid is any presentation offered not as evidence but rather to assist the trier of fact in understanding evidence or argument." On the jury room, the Note explains that letting an aid into deliberations "runs the risk that the jury may unduly emphasize the testimony of a witness with whom it was used, or otherwise misinterpret" its purpose, while trial courts retain discretion to permit access for good cause. On preservation, the Note is direct: "While an illustrative aid is not evidence, if it is used at trial it must be marked as an exhibit and made part of the record, unless that is impracticable under the circumstances."

Stop calling it a demonstrative in federal court

The Advisory Committee chose "illustrative aid" over "demonstrative evidence" because "demonstrative" had become ambiguous, used both for illustrative aids and for real or substantive exhibits such as a physical object. Federal vocabulary has shifted. Stop treating "demonstrative" as a term of art in federal court, and stop writing it into your reports as though it carried a legal meaning that everyone shares.

37.1Purge "demonstrative evidence" from your federal report template and replace it with either "illustrative aid under Federal Rule of Evidence 107" or "substantive evidence," chosen deliberately for each exhibit.

The older cases sort your exhibits into three categories

The rule is new but the reasoning behind it is not, and the pre-2024 cases still explain why the lines fall where they do. United States v. Bray, 139 F.3d 1104 (6th Cir. 1998), is the most useful single federal citation because it identifies three categories rather than two. Rule 1006 primary evidence summaries, which "must fairly represent and be taken from underlying documentary proof which is too voluminous for convenient in-court examination" and where "the summary, and not the underlying documents, is the evidence to be considered by the factfinder." Pedagogical devices under Federal Rule of Evidence 611(a), which summarize or illustrate admitted evidence, are not themselves admitted, may reflect the proponent's inferences and conclusions, and are "more akin to argument than evidence." And a middle category, the secondary evidence summary, "admitted in evidence not in lieu of the evidence they summarize but in addition thereto," about which the jury should be instructed that the summary "is not independent evidence of its subject matter, and is only as valid and reliable as the underlying evidence it summarizes."

A photo board, synchronized timeline, comparison sheet, or overlay may serve different purposes. Have counsel classify the actual exhibit under current rules and identify the appropriate foundation and limiting instruction. Format alone does not place it in Bray's middle category.

United States v. Janati, 374 F.3d 263 (4th Cir. 2004), adds the instruction duty, stating that whenever pedagogical charts are used "the court should make clear to the jury that the charts are not evidence themselves, but are displayed to assist the jury's understanding of the evidence." United States v. Wood, 943 F.2d 1048 (9th Cir. 1991), states that such devices "should be used only as a testimonial aid, and should not be admitted into evidence or otherwise be used by the jury during deliberations." And Pierce v. Ramsey Winch Co., 753 F.2d 416 (5th Cir. 1985), holds that pedagogical charts "are not themselves evidence and, absent the consent of all parties, they should not be sent to the juryroom." That carve-out, absent the consent of all parties, is the direct ancestor of Rule 107(b)(1).

What one exemplar in the jury room cost a party

In Baugh ex rel. Baugh v. Cuprum S.A. de C.V., No. 12-2019 (7th Cir. Sept. 13, 2013), a products liability case about a ladder, an exemplar ladder was used at trial by the defense expert to illustrate his oral testimony and was expressly treated as demonstrative, not evidence. Over objection, the district court sent it to the jury room. The jury returned a defense verdict shortly afterward. The Seventh Circuit held that "the general rule is that materials not admitted into evidence simply should not be sent to the jury for use in its deliberations," that "demonstrative exhibits that are not admitted into evidence should not go to the jury during deliberation, at least not without consent of all parties," and that sending the ladder back was an abuse of discretion. Finding "a reasonable possibility that the unadmitted materials altered the jury's verdict," and noting that the jury reached its verdict shortly after it had the chance to "examine, step on, and manipulate the exemplar ladder," the court reversed and remanded for a new trial.

Baugh illustrates the risk of sending an unadmitted exemplar into deliberations under the circumstances of that case. Determine the status and permitted use of each animation, model, overlay, or exemplar under the applicable rules, including Rule 107.

How you put an animation into the record

Subsection (c) is the sleeper, and it is where this book's central argument pays off. An illustrative aid that is never admitted must still be marked as an exhibit and made part of the record. For a photograph on a board that is easy. For an animation, an interactive model, or a synchronized video timeline, "entered into the record" cannot sensibly mean a still frame, because an appellate court cannot evaluate what the jury saw without knowing how it was shown. Lodge the actual media file, and lodge with it a description of playback conditions: resolution, aspect ratio, frame rate, playback speed, screen size, and room lighting. Nothing in the rule spells that out. That is the point. Where the rule does not specify, your documented method is what fills the gap, exactly as it does in the absence of a governing imaging standard.

37.2For every dynamic aid, prepare a one page playback specification and lodge it with the media file, so the record shows what the jury saw.

37.3Ask counsel, before trial, whether the aid will be offered as evidence or used only illustratively, and build the labeling and the documentation to match that answer.

Two opposite design pressures, and you must pick one first

Design an illustrative aid for clear use during testimony and an evidentiary exhibit for its admitted purpose. Rule 107 also permits an aid in deliberations with all-party consent or a good-cause order. Resolve the proposed use with counsel before building the presentation.

Chapter 37 Checklist: Aids and Evidence

Chapter 38Animation, Simulation, and the Line Between Them

An animation can illustrate an opinion; a simulation uses a model to calculate results. Examine what each component does and how the proponent intends to use it.

The analytical role and proposed use of the software output affect its foundation and disclosure. A label alone does not determine admissibility, and an animation can incorporate simulation results that require separate support.

Where the courts draw the line, in their own words

Take the definitions from the verified cases rather than from a vendor's brochure. The Supreme Court of Pennsylvania, in Commonwealth v. Serge, No. 150 MAP 2004, decided April 26, 2006, affirming the Superior Court decision reported at 837 A.2d 1255 (Pa. Super. 2003), described a computer generated animation as "a drawing... which, when assembled frame-by frame, produce[s] the image of motion," and as "merely a graphic representation depicting the previously formed opinion of a witness." On the other side of the line, "computer-generated simulations do not depict witness opinion; rather, the computer program... draws a conclusion... the end product of a simulation represents the computer program's conclusion." The trial court's jury instruction, quoted in the opinion, put simulation in plain language: "data is entered into a computer, which is preprogrammed to perform certain calculations by applying... the laws of physics, mathematical formulas... in order for the computer itself to draw conclusions."

People v. Cauley, 32 P.3d 602 (Colo. App. 2001), states the reason the line falls where it does, in one clause worth memorizing. Simulations are "recreations or experiments based upon scientific principles and data" in which "data is entered into a computer, which is programmed to analyze and draw conclusions from it," while "an animation is distinguishable from a simulation because it is demonstrative, rather than scientific, and the validity of the conclusion does not depend on proper application of scientific principles."

Ask whether the software merely depicts an independently supported opinion or generates a result relied on in the analysis. Identify any mixed functions. Calculations used to render an illustration do not automatically make the whole exhibit a substantive simulation.

The two labels do not carry the same burden

The consequences are asymmetric and severe. An animation, in federal court after December 1, 2024, travels as an illustrative aid under Federal Rule of Evidence 107. Its foundation, as the verified state cases lay it out, is authentication as a fair and accurate representation of the testimony it illustrates, relevance, and a Rule 403 balance with attention to inflammatory content. A simulation is substantive proof, which pulls Federal Rule of Evidence 702 and Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), down on your head, along with everything those authorities carry: testability, peer review, known or potential rate of error and the existence of standards controlling the technique's operation, and general acceptance, all of them non-exclusive factors under a "flexible" inquiry. Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), removed any argument that a physics engine escapes because it is engineering rather than science: the gatekeeping obligation "applies not only to testimony based on 'scientific' knowledge, but also to testimony based on 'technical' and 'other specialized' knowledge."

38.1: Identify whether the software illustrates an opinion, calculates results relied on in the opinion, or does both. Document the functions and intended use before building the exhibit.

What a simulation foundation has to establish

The best verified statement of what a simulation foundation requires comes from a case about a chart, not a movie. Bray v. Bi-State Development Corp., 949 S.W.2d 93 (Mo. App. E.D. 1997), concerned a computer generated chart of light intensity levels, the output of an engineering calculation program. The court reasoned that the function of such programs "is to perform rapidly and accurately an extensive series of computations," and that "just as experts may base their testimony on calculations performed by hand, they may perform the same calculations using a computer." The three part foundation it adopted requires that the computer is functioning properly, that the input and underlying equations are sufficiently complete and accurate and disclosed to the opposing party, and that the program is generally accepted by the appropriate community of scientists. The expert there testified to the software's reliability, to industry reliance on it, and, most usefully, to verification against actual field measurements.

Read element two again. Disclosure of inputs and equations is written into the foundation itself. Read element three with a caveat: Missouri applied a general acceptance test, and in a Daubert jurisdiction general acceptance is one factor rather than the test. And note what none of the verified cases supplies: not one of them states a known or potential error rate requirement for a computer simulation in so many words. That factor applies through Rule 702, and the 2023 Committee Note reinforces it, but do not attribute an error rate holding to any of these decisions.

The generosity shown to animation comes with conditions

Now the animation side, where the federal courts have been generous and the generosity has conditions. Hinkle v. City of Clarksburg, 81 F.3d 416 (4th Cir. 1996), holds that "video taped evidence purporting to recreate events at issue must be substantially similar to the actual events to be admissible," moderating that requirement where the events themselves were disputed, and then draws the distinction that matters: "the difference between a jury believing that they are seeing a repeat of the actual event and a jury understanding that they are seeing an illustration of someone else's opinion of what happened." The instruction given told the jury the animation "is not meant to be a recreation of the events, but rather it consists of a computer picture to help you understand" the expert's opinion. The court added that there was no reason for the jury "to credit the illustration any more than they credit the underlying opinion," and encouraged trial judges "to first examine proposed videotaped simulation evidence outside the presence of the jury to assess its foundation, relevance, and potential for undue prejudice."

That sentence is your best argument for a pretrial hearing, in either direction.

Robinson v. Missouri Pacific Railroad, 16 F.3d 1083 (10th Cir. 1994), is worth knowing because the technique was physical rather than digital: the expert built a scale model of a nighttime grade crossing from physical evidence and photographs, then shot frame by frame video by incrementally moving the train and the car. Affirmed, given the exhibit's limited, solely illustrative purpose, with the trial court emphasizing to the jury that it was not a recreation. The animation logic is medium independent. Stop motion, computer graphics, and a hand drawn sequence are governed the same way.

Datskow v. Teledyne Continental Motors, 826 F. Supp. 677 (W.D.N.Y. 1993), contributes two details you will use. The animation illustrated an expert's theory of the origin and spread of an engine fire and was characterized as illustrative, not a recreation. The court ordered the tape played with the volume turned off, because radio communications on the soundtrack would lend a false sense of authenticity. That is a ruling about an incidental production choice creating verisimilitude nobody had earned, and it should govern your sound design, your motion blur, your lens flare, your smoke, and your skid noise. The second detail deserves skepticism rather than citation: the court reasoned that jurors are fairly sophisticated media consumers and that proper instruction mitigates overvaluation. That was a 1993 assumption about media literacy. Applying it without comment to a photorealistic exhibit rendered today is not an argument, it is a quotation.

Finding the simulation wearing an animation label

Ask what the software calculated, how timing was established, and which outputs support the opinion. Review the project file, inputs, version, and render settings. If analysis and illustration are combined, identify the foundation needed for each rather than classifying the entire exhibit from one computed number.

38.2Ask the opposing animator one question first: which numbers in this exhibit came out of the software rather than into it?

38.3: Identify the support or disclosed assumption for every material feature in an animation, and distinguish illustration from recorded evidence.

Ask for the limiting instruction in your own case too

Ask also for the limiting instruction, in your own case as well as against. All four verified animation decisions involved one. Serge's cautionary instruction remains the most quotable sentence in the field: the animation "is a demonstrative exhibit, not substantive evidence," offered "solely as an illustration" of a party's version of events, and "you should not confuse art with reality."

Chapter 38 Checklist: Labeling the Exhibit

Chapter 39Print, Projection, and the Juror in the Back Row

Your exhibit is not the file. Your exhibit is what reaches the eye of the juror farthest from it.

The one number every resolution rule comes from

A 20/20 acuity model offers a starting point for display design. The critical gap in a standard eye-chart letter subtends about one arcminute, corresponding to distance divided by 3438. Actual readability also depends on contrast, font, illumination, viewing time, and the viewer.

Under that acuity model, one pixel per one-arcminute element corresponds to 3438 divided by viewing distance in inches, or 286.5 divided by distance in feet. Treat this as a planning estimate and test the actual exhibit for readability.

The model gives about 286 pixels per inch at 12 inches and 143 at 24 inches. These values help explain familiar printing targets, but do not establish a sufficient resolution for every viewer or task. Allow margin and inspect the actual output.

39.1Compute the pixels per inch your exhibit needs from the distance of the closest realistic viewer, not from a rule of thumb and not from the average viewer.

What the board everyone wants would really cost

A 40 by 60 inch exhibit requires 216 megapixels at 300 pixels per inch and 54 megapixels at 150. At 48 pixels per inch it requires about 5.5 megapixels. Compare the actual file, viewing distance, and feature size rather than assuming every modern camera meets the requirement.

So the board is fine, until a juror walks up to it. At 2 feet the requirement is 143 pixels per inch, which is 5,720 by 8,580 pixels, or 49 megapixels. Boards get approached. Design for the closest viewer or limit the approach, and understand that your three options are a lower resolution matched to a real viewing distance, a higher resolution or pixel shift body, or stitching. Stitching is a process, and a process gets disclosed and documented like every other process in this book.

For calibration: a 24 megapixel camera produces a 6,000 by 4,000 pixel file, which prints 24 by 36 inches at 167 pixels per inch. It cannot reach 300 at that size without interpolation, and interpolation is not new information. It is arithmetic that invents pixels.

The projector, not your file, sets the ceiling

The projector, not the file, is the ceiling. A high definition projector, meaning 1920 by 1080 pixels, delivers 2,073,600 pixels, which is 2.07 megapixels, no matter what you feed it. A 45 megapixel file is downsampled roughly 22 to 1 to get there. A 24 megapixel file is downsampled about 11.6 to 1.

It is worse than that, because your photograph does not fit the screen. A camera file is 3:2. A high definition screen is 16:9. Letterbox the full frame at full height and it occupies 1,620 by 1,080 pixels, which is 1.75 megapixels, or roughly eighty-four percent of the projector's pixels, with black bars down each side. On a legacy 1024 by 768 courtroom projector, a 3:2 image fits full width at 1,024 by 683 pixels, which is 0.70 megapixels. An ultra high definition projector delivers 3840 by 2160, or 8.29 megapixels, and many courtrooms do not have one.

39.2If a detail must be seen on a screen, prepare a cropped detail view as a separate, disclosed exhibit. Do not expect a juror to find it inside a full frame downsampled to two megapixels.

Check element size, contrast, and resolution

For a 1080-pixel-high display and the one-arcminute model, image height is about 0.314 times viewing distance when one pixel subtends that angle. This is a planning estimate, not a visibility guarantee. Test the smallest relevant feature and text at the actual seats.

So compute the elements. Minimum element height equals the viewing distance multiplied by the angle in arcminutes, divided by 3438. At 5 arcminutes, the recognition threshold, a character at 20 feet must be 0.35 inches tall to be recognized at all. Threshold is not a design target. A juror reading a dimension label for two seconds while listening to your testimony needs margin, and a defensible target is 15 to 20 arcminutes, or 1.05 to 1.40 inches of character height at 20 feet.

At 20 feet, a 15-arcminute target gives a character height near 1.05 inches. If the smallest text occupies two percent of image height, the image would need to be about 52.5 inches tall; at one percent, twice that. Enlarging the text can be more practical than enlarging the whole display. Test the result in the room.

39.3Design exhibits so the smallest element occupies at least two percent of image height, and measure that fraction in your own file rather than assuming it.

Aspect ratios throw away evidence without telling you

Check the file and display aspect ratios. Filling a 16:9 screen with a 3:2 image requires cropping about sixteen percent of its height unless the image is distorted; a 4:3 image requires about twenty-five percent. Preserve the full frame and disclose any crop rather than assuming all dedicated cameras use 3:2.

Fit the full frame to the display with borders where needed. For a detail crop, preserve the original, disclose coordinates, label the view, and make the full frame available. A print whose aspect ratio differs from the source can use borders rather than requiring a crop.

Check courtroom lighting before choosing the display

Confirm courtroom lighting, permitted adjustments, screen size, and installed display equipment with the deputy. Ambient light reduces projected contrast, especially in dark tones. Evaluate a projector or emissive display under the actual conditions rather than assuming a fixed lumen threshold or universal display advantage.

Two audiovisual industry standards govern this territory and neither can be quoted here. The standard jointly issued by the American National Standards Institute and the Audiovisual and Integrated Experience Association, designated V201.01:2021, "Image System Contrast Ratio," defines four contrast ratios based on content viewing requirements, and those four values sit behind a paywall. Its companion, designated 202.01:2016, "Display Image Size for 2D Content in Audiovisual Systems," published May 2016, sets required display size and viewing positions for two stated viewing needs, Basic Decision Making and Analytical Decision Making, and its thresholds are paywalled as well. Do not print figures attributed to either document that you have not read in the document itself. The widely repeated rule placing the farthest viewer at four, six, or eight times the image height traces to no authoritative source at all. Treat it as trade folklore and use the acuity arithmetic above, which you can derive on the stand with a pencil.

That is the Chapter 4 argument in a different costume. Where the standard is unavailable, the documented method is what you offer, and first principles are more defensible than a number you cannot source.

Brightening an image for projection is an alteration

Brightening an image for projection is an alteration. So is a contrast adjustment, a gamma change, a crop, and a resize. Never adjust the original; work on a copy. Record the source filename and its hash, the software and version, the ordered list of operations, and the numeric parameter of each, in the form "black point 0 to 18, white point 255 to 255, gamma 1.00 to 1.35, no local adjustments, no cloning, no sharpening." Then apply the reproducibility test: could a comparably trained person, given your original and your notes, produce your exhibit? Bring the original to court. And never run content aware fill, generative fill, artificial intelligence upscaling, or artificial intelligence denoising on an evidentiary image, because those tools synthesize pixels that were never recorded.

39.4Disclose every display adjustment in the report, name the numeric parameters, and bring the unadjusted original to court.

Chapter 39 Checklist: The Back Row

Chapter 40Testifying About Your Own Images

Every photograph you have ever taken is an unanswered question until you answer it out loud.

Foundation is the first thing you can lose

Foundation is the first thing that happens and the fastest thing to lose. Under Federal Rule of Evidence 901(a), the proponent must produce evidence "sufficient to support a finding that the item is what the proponent claims it is." That is a low bar and it is not a technical one. If you took the photograph and you were there, you say what the scene was, when you were there, that you made the image, and that it fairly and accurately depicts what you observed. If nobody was there, as with a time lapse camera or an unattended recorder, the foundation comes from the process instead: how the device was set up, how it was activated, what interval it recorded at, what date it carried, and who held the medium afterward.

Answer those questions in the order the rule cares about, and answer them in short sentences. Foundation testimony is not where you show range.

How to explain a method to twelve strangers

Explain the term, its practical meaning, and its relevance. For example: depth of field is the distance range that appears acceptably sharp under stated viewing conditions. Keeping the feature and scale sharp supports measurement, but alignment, scale placement, calibration, and uncertainty also require evaluation.

Explain the instrument, result, units, and uncertainty in terms appropriate to the audience. Check understanding rather than assuming a description of the tool ensures comprehension of the number.

40.1: Rehearse concise technical explanations in plain language. Use additional sentences when the method or its limits require them.

Concede on purpose, and concede first

Conceding is the part experts get wrong, and it is the fastest credibility move available to you. The 2023 Advisory Committee Note to Federal Rule of Evidence 702, as amended effective December 1, 2023, is addressed to this audience by name. It states that forensic experts "should avoid assertions of absolute or one hundred percent certainty, or to a reasonable degree of scientific certainty, if the methodology is subjective and thus potentially subject to error," that the judge should where possible receive an estimate of the known or potential rate of error, and that opinion testimony about feature correspondence "must be limited to those inferences that can reasonably be drawn from a reliable application of the principles and methods." Photographic comparison, image authentication, and reverse projection are subjective or feature comparison methods sitting squarely inside that paragraph.

State the method's limits on direct examination. Distinguish the scene recorded by the camera from a witness's perception. Explain color controls and measurement uncertainty, including limits that could not be quantified. Disclosure supports review but does not remove legitimate challenges.

The lens, the light, the clock, and the file

Prepare to explain lens geometry, lighting, timing, and file integrity, along with any other feature relevant to the opinion.

For geometry questions, state focal length, sensor format, camera position, calibration, and correction status. Explain the projection model used and assess whether nominal parameters were adequate. Describe how framing and viewpoint affect the proposed interpretation.

The light question is about honesty. Expect "was that how it looked?" The answer that holds describes the ambient conditions you metered on site, the lights you brought and where they were, whether flash was direct or off camera, whether a color reference target is in the frame, and what your exposure settings were. Then the concession that does more work than any of it: the photograph is evidence of the scene, not evidence of what a person could see, because a camera and a retina do not share a response curve, an integration time, or, at night, even a photoreceptor class.

The clock question is about trust. Expect "how do you know when that was taken?" The answer that holds is that you verified the camera clock against a known reference before the first frame, that you recorded the reference and the offset if there was one, that you noted the time zone and the daylight saving state, and that the frames run in a sequence consistent with your photograph log. The wrong answer is that the camera said so. A camera clock is a free running oscillator that somebody set once, and every opponent knows it.

40.2: Verify and record the clock before the first frame of every job, and check it again at the end.

Explain which files are originals, how they were transferred and verified, and what processing produced the exhibits. Identify omitted or deleted frames and follow counsel's production directions. Transfers through email, messaging, or cloud services require examination because their metadata effects depend on the operation and settings.

Document and validate the method

Rule 702 requires reliable principles and methods and reliable application to the facts, along with its other conditions. A written procedure makes the work reviewable; it does not make the procedure a governing standard or establish reliability by itself. Document validation, performance, assumptions, and limitations.

Which is why the answer to almost every hard question from the stand takes the same shape. Here is what I did. Here is why I did it that way. Here is what I wrote down at the time. Here is what my method cannot tell you.

The craft of testifying, the pauses, the pace, the management of a hostile examiner, the preparation sessions with counsel, belongs to a different book in this series, Being a Great Expert Witness. This one ends where the image reaches the courtroom.

Everything in these forty chapters reduces to a single instruction, and you have read it in a dozen forms. Decide what question the frame must answer. Capture it to the higher standard. Preserve the original. Write down what you did.

These practices preserve a record for later review. They do not guarantee that the original capture was accurate or that a proposed interpretation is justified.

Chapter 40 Checklist: The Stand

Appendices

Appendix A. The Master Field Checklist

Every checklist in this book, consolidated in the order a case runs. Five hundred ninety-eight items.

Print it, work it, and put the worked copy in the file. A checklist you filled out at the scene is a contemporaneous record. A checklist you filled out afterward is a memory, and a competent opponent will make you say which one it was.

Part One. The Frame

1. The Two Kinds of Image

2. The Instrument

3. Eye Versus Sensor

4. Standards and Authority

5. The Kit

Part Two. The Craft

6. Exposure

7. Focus and Depth

8. The Lens

9. Light

10. Beyond Visible Light

11. Color You Can Defend

12. Scale and Geometry

13. Format and Artifacts

Part Three. The Scene

14. Before You Leave

15. Overall, Midrange, Close-Up

16. Injuries and People

17. Parts, Machines, and Failure Surfaces

18. Difficult Scenes

19. Night and Visibility

20. Aerial Documentation

21. Three-Dimensional Capture

Part Four. The Record

22. Video Fundamentals

23. Rolling Shutter and Fields

24. High-Speed Capture

25. Surveillance Video Collection

26. Recording the Witness

27. Testing and Reenactment

Part Five. The Chain

28. The File's Own Testimony

29. The Second Chain

30. The Archive

31. Foundation

32. Authentication and Fakery

33. Disclosure

34. Preservation

35. Access and Permission

Part Six. The Verdict

36. The Restrained Exhibit

37. Aids and Evidence

38. Labeling the Exhibit

39. The Back Row

40. The Stand

Appendix B. Camera Settings Quick Reference

Ten scenarios, one page each. Every value below traces to a chapter. Where a chapter gives a verified published number, this appendix gives that number and names it as verified. Where no chapter supplies one, the entry is marked as a starting point, which means a defensible place to begin and a value you adjust on site and record in the log. A starting point is not a rule, and testifying to one as though it were a rule is how a good method gets impeached.

Two conventions run through all ten tables. The sensitivity setting is the control marked ISO on every camera. Raw means the camera's sensor-native raw file, confirmed lossless, and JPEG means the compressed format most cameras produce by default.

B.1 General Scene Documentation in Daylight

B.2 Interior Scene With Mixed Light

B.3 A Part or Fracture Surface on a Bench

B.4 Tool Marks and Impressions With Oblique Light

B.5 An Injury on Skin

B.6 A Large Dark Space Requiring Painting With Light

B.7 Night Visibility Documentation

B.8 Overlapping Capture for Photogrammetry

B.9 Video of a Walkthrough

B.10 High-Speed Video of an Impact Event

Appendix C. Equipment by Budget Tier

Choose equipment for the required capture, measurement, and preservation tasks. Verified scales and color references deserve consideration alongside camera and lens performance.

Read the tiers as planning categories. Notes, time references, and hashing tools support documentation; camera controls support capture; redundancy reduces single-device loss; specialized equipment serves defined tasks. None of those categories alone protects the complete record.

Prices are July 2026 examples. Confirm current costs and compatibility before purchase. Camera price does not establish image quality for the task or evidentiary reliability; evaluate equipment, method, documentation, and preservation together.

For each item, identify the capture, verification, or preservation function it serves. Do not equate aesthetic improvement with evidentiary reliability.

Tier 1. What You Already Own

Determine the phone's capture mode and processing before using its images for measurement or color analysis. Multi-frame and learned processing require evaluation; phone origin alone does not establish that the image is a composite or unusable.

Tier 2. Entry, Under $1,000

Tier 3. Working, $1,000 to $3,000

This is the book's default recommendation. The defining feature is not the sensor.

Tier 4. Full Capability, Above $3,000

What Not to Buy First

This is the useful part of the appendix, and it is short.

Prioritize the scales, color references, lenses, storage, and camera controls required by the assignment. Evaluate compatibility before buying the body.

Choose viewpoint and focal length for the intended spatial interpretation. A distant viewpoint can compress apparent depth, but focal length alone does not make a scene image misleading. Record the position and provide contextual views.

Do not buy an ultrawide lens because it fits more in. A 15 millimeter prime measured 6.12 percent barrel distortion uncorrected, and switching the camera's correction on moved its field of view by about 4 degrees and its effective focal length by a full millimeter, silently.

Do not buy a zoom for metrology. Use a prime, calibrate that specific body and lens at that specific focal length and focus distance, and keep the calibration date on the lid of the case.

Test indoor microphones in the actual room. Tube design, directionality, placement, reflections, and background noise affect the recording. One shotgun measurement does not establish that all shotgun microphones are unsuitable indoors.

Do not buy a thermal camera expecting an infrared photograph. It records emitted long-wave radiation, not reflected light, its detector may be 320 by 240 pixels for the entire scene, and it reports a temperature only after you assume an emissivity and a background temperature.

Use phone or tablet scans for dimensional opinions only when validation supports the required accuracy on the actual subjects and conditions. Preserve the available source data and state export limitations.

Do not buy a solid state drive or a shelved hard drive as your archive. Federal guidance gives expected shelf life for unused media as under 1 year for a solid state drive and under 2 years for a hard disk drive, neither recommended for archival.

For an unreadable exhibit, check feature size, contrast, file resolution, scaling, and display resolution. A 1920 by 1080 display has about 2.07 million pixels, so a larger source file alone cannot resolve every display problem.

Appendix D. Templates

Five forms, written to be copied or printed. Fill them in ink, on site, before you move the camera. A form completed afterward reads like a form completed afterward.

D.1 Photograph Log

Use this from frame one of every session, not from the frame where the case got interesting. It is the document you will be handed on the stand, and a gap in it invites a question you cannot answer well.

Case name: ______________________________________________ File number: ______________________

Date: ____________________ Location: ___________________________________________________

Photographer: ___________________________________________ Session start: ____________________

Camera body make and model: ______________________________ Body serial number: ______________

Clock reference photographed at start: ___________________ Reference time shown: ____________

Camera time recorded: ____________________________________ Signed offset: __________________

Time zone standing in: ___________________________________ Daylight saving state: ___________

Location tagging policy for this session: on / off, and reason: _________________________________

Hazards, protective equipment, and access method: _______________________________________________

Anything you could not photograph, and why: ____________________________________________________

Clock reference photographed at end: _____________ Reference time: _____________ Camera time: _____________

Session end: ____________________ Total frames captured: ____________________

Frames deleted in the field: none. If any, explain in full: ____________________________________

Signature: ______________________________________________ Date: ______________________________

D.2 Chain of Custody Record for Digital Image Files

Use one page per case, opened the day you first touch a card or receive a file, and treat it as an exhibit from that day forward. It records the second chain of custody, the one for the data, which exists in parallel with the chain for the physical card.

Case name: ______________________________________________ File number: ______________________

Media identifier: _______________________________________ Capacity: ________________________

Source: camera card / drive received from another party / export from a recorder / other: ______

If received from another party, from whom, in what packaging, and in what condition: ___________

Write blocker used on ingest: yes / no. Make, model, serial number: ___________________________

Ingest method: copy only. Files moved, cut, emailed, texted, or shared at any point: yes / no ___

Primary algorithm: the Secure Hash Algorithm at 256 bits. Second algorithm used: ______________

Original set designated and marked read-only on: ____________________ By: _____________________

Working copy created on: ____________________ Verified against original by hash: yes / no _____

Neural denoise, upscale, or other machine processing applied to any file: yes / no. If yes, list the file, the tool, the version, and the date: _________________________________________________

Copies held at, with medium named for each: 1) ________________ 2) ________________ 3) __________

Write-once or locked immutable copy held at: ___________________________________________________

Card retired to labeled sleeve on: ____________________ Card released for reuse by counsel on: ____________________

Verification schedule: manifest revalidated (quarterly) ____________ offsite restore tested (annually) ____________ Result logged: ____________

Irregularities encountered and what was done about them, recorded on the day they happened: _________________________________________________________________________________________________

Retention period obtained in writing from retaining counsel and carrier: ________________________

Signature: ______________________________________________ Date: ______________________________

D.3 Scene Documentation Plan

Fill this out before you leave the office, and carry it on paper to the scene so you can shoot from it. It is one page with four things on it, and the first one generates the other three.

Case name: ______________________________________________ File number: ______________________

Site: ___________________________________________________ Inspection date and time window: ____

1. The question the imagery must answer, in one sentence.

_________________________________________________________________________________________________

_________________________________________________________________________________________________

2. Shot list, built backward from that sentence. Mark each item O for overall, M for midrange, C for close-up, and S for any item requiring a scale.

Comparison items, adjacent conditions, and absences to photograph: ______________________________

Items you believe are irrelevant and will photograph anyway: ____________________________________

3. Equipment the shot list requires. Bodies ______ Lenses ______ Tripod ______ Flash and triggers ______ Scales ______ Color target ______ Gray card ______ Cards ______ Batteries charged ______ Write blocker ______ Laptop ______ Protective equipment ______ Second, disposable kit for a hostile scene ______ The plan itself, on paper ______

4. Constraints already known.

Access authority: order / stipulation / subpoena / owner consent. Cite it: ______________________

Restrictions on what may be photographed (faces, security systems, other tenants, proprietary processes): _____________________________________________________________________________________

Who may attend, who may operate equipment, may you measure, may you test, may you remove anything: _________________________________________________________________________________________________

Escort, site orientation, and protective equipment requirements: ________________________________

Time window, and what happens if it runs out: ___________________________________________________

Sunrise ________ Sunset ________ Sun position at the hour that matters ________ Moon phase ______

Weather forecast ________ Tide and current ________ Plant shutdown window ________

Protective order and retention terms confirmed in writing with counsel: yes / no. Date: _________

Location tagging policy for this inspection: ____________________________________________________

Second visit available: assume no. If a second visit is truly available, say why: _______________

Rough complete pass in all three tiers to be shot first, before any light is set up: yes

Prepared by: ____________________________________________ Date: ______________________________

D.4 Surveillance Video Collection Record

Complete this form at the recorder while access and settings are available. Record anything unavailable and identify possible follow-up methods.

Case name: ______________________________________________ File number: ______________________

Legal authority for the collection: ____________________________________________________________

Incident date, time, and location: _____________________________________________________________

Site address: ___________________________________________ Contact and title: _________________

Arrival time: ____________ Recorder located at: ______________________________________________

Photographs taken of the unit, the cameras, and all connections as found, before touching anything: frames ____________ to ____________

Clock. Photograph of the recorder's on-screen clock together with a known-good time source in one frame: frame ____________

Recorder clock displayed: ____________ Known-good time displayed: ____________

Signed offset, with direction stated in words: __________________________________________________

The time and date on the recorder were not changed. Confirmed: yes / no ________________________

The unit.

Make ____________ Model ____________ Serial number ____________ Firmware version ______________

Credentials used ____________________ Channels capable ________ Channels connected ___________

Storage capacity ____________ Used space ____________ Earliest recorded date ________________

Overwrite settings ____________________ Deletion or retention schedule ________________________

Per camera.

Export.

Native or proprietary export completed: yes / no. Format: ____________________________________

Viewer application and codec taken from the device: yes / no. Version: ________________________

Open-format export taken second, as a backup and not as a replacement: yes / no ________________

Time margin acquired on both sides of the incident window: from ____________ to ________________

Destination media identifier: __________________________________________________________________

Acquisition hash values recorded on this page: yes / no ________________________________________

Playback verified on a portable computer on scene, with dates and times displaying correctly: yes / no. Verified by: ____________________ Time: ____________

Encoder tag in the file metadata, with corroborating evidence of any processing; the tag alone does not establish who created the export: ____________________________________________________

System restored to its original state: yes / no Exit time: ____________

Chain of custody initiated on: ____________________ Signature: _______________________________

D.5 Consent to Record an Interview

Use this before any recorded interview, and read the announcement aloud on the recording itself so the consent exists inside the evidence rather than only on paper. The form is a starting point only, and retaining counsel must approve it for the jurisdiction before you use it, because consent law varies by state and this book is not legal advice.

Notice. This form is a starting point. Retaining counsel must review and approve it for every jurisdiction the conversation touches before it is used. A minority of states require the consent of every party, several prohibit secret or hidden-device recording rather than requiring consent, one requires notice rather than consent for in-person conversations, and at least one has no wiretapping statute at all. Apply the most restrictive rule among every jurisdiction the conversation touches, and confirm that rule with counsel in writing before the interview.

Case name: ______________________________________________ File number: ______________________

Date: ____________________ Start time: ____________________ End time: ______________________

Location of the interviewer: ___________________________________________________________________

Location of the person being recorded, as stated by that person: _______________________________

(Ask the witness where he or she is physically located, and record the answer. Area codes prove nothing.)

Every jurisdiction this conversation touches: __________________________________________________

Rule applied, and confirmed in writing by counsel on: __________________________________________

Statement to be read aloud on the recording, before any substantive question.

"My name is ______________________________. Today is ______________________. The time is ______________. I am recording this conversation, in audio and video, on two devices. This recording is being made in connection with ______________________________. Do I have your permission to record this conversation?"

Answer given, verbatim: ________________________________________________________________________

Recording device 1: make, model, media identifier: _____________________________________________

Recording device 2, independent power and independent media: ___________________________________

Sample rate 48 kilohertz, 24 bits or 32-bit float, uncompressed. Confirmed: yes / no ___________

Everyone present in the room or on the line, by name and role: _________________________________

Is this person represented by counsel in this matter, to your knowledge: yes / no / unknown ____

If yes, stop and call retaining counsel before proceeding: confirmed ___________________________

Consent of the person being recorded.

I have been told, before the recording began, that this conversation is being recorded in audio and video. I understand who is making the recording and in what matter. I understand that I may stop the recording at any time, may decline to answer any question, and may ask that any portion be stopped or that the recording be ended.

Printed name: ___________________________________________________________________________________

Signature: ______________________________________________ Date: ______________________________

Interviewer signature: __________________________________ Date: ______________________________

Retaining counsel approved this form for this jurisdiction on: ________________________________

Appendix E. All 145 Tips in One Table

Every numbered tip in the book, in order. The number is chapter and tip, so 12.3 is the third tip in Chapter 12. Read the chapter for the reasoning. Use the table to refresh before a site visit or a deposition.

Appendix F. Glossary

Every entry is written for a reader who has never held a camera, and every definition matches how the book uses the term.

Adaptation. The slow shift in the eye's sensitivity as light levels change. Full dark adaptation takes roughly forty minutes; bleaching fifty percent of the rod pigment raises the visual threshold by ten log units.

Airy disk. The blur spot a point of light becomes after passing through an aperture. Its diameter is 2.44 times the wavelength times the f-number, which is why small apertures cost resolution.

Alternate light source. A narrowband lamp that makes a subject fluoresce, viewed through a barrier filter that blocks the excitation light. Record the wavelength and the filter combination for every frame.

Animation. A moving graphic used to illustrate a previously formed opinion. Its legal treatment depends on the proposed use and any analytical results incorporated into it.

Aperture. The adjustable hole inside a lens, named by the f-number. Each step on the scale halves or doubles the light. Smaller number, bigger hole.

Arcminute. One sixtieth of a degree. The unit of visual angle behind both the 20/20 acuity standard and the perpendicularity tolerance on a forensic scale.

Aspect ratio. The proportion of width to height. Camera files are usually 3 by 2; screens are usually 16 by 9, so filling a screen with a photograph discards about sixteen percent of its height.

Authentication. Producing evidence sufficient to support a finding that an item is what you say it is. It is not a finding that the image is true, and it does not by itself get the exhibit admitted.

Available light. The light already present at a scene. The published trigger for available light technique is that some existing light is present and a single flash will not produce a proper exposure.

Banding. Visible steps in a tonal gradient. Compression or other quantization can cause it; compare originals and processing before assigning a cause.

Barrel and pincushion distortion. Lens errors in which straight lines bow outward or inward. Barrel lives at the wide end, pincushion at the long end, and a mixture of both is called mustache distortion.

Base sensitivity. The lowest sensitivity setting the camera offers, where read noise is highest in electrons but the signal is largest. Use it whenever a tripod and time allow.

Bidirectional frame. A video frame encoded by interpolating between the nearest self-contained and predicted frames. It is instructions, not a picture, and cannot be verified in isolation.

Bit depth. How many tonal levels a file records per channel. Baseline JPEG is always 8 bits, or 256 levels. A 14-bit raw carries 16,384.

Bit rot. Corruption of stored data over time. Manufacturer read-error specifications are bounds under stated conditions, not measured predictions for a particular restore. Verify archives with checksums and independent copies.

Blocking. Visible block boundaries caused by compression. Repeated grid alignment can help identify the artifact, but does not by itself prove a feature is nonphysical.

Bracketing. Shooting the metered exposure plus frames one and two stops under and over. It is not a hedge; it is a method, and you keep every frame including the ones you would never show.

Chain of custody. The documented record of who held an item, when, and what they did to it. In digital work there are two chains, one for the physical card and one for the file.

Chroma subsampling. Sharing one color measurement across a block of pixels. The common scheme discards three-quarters of the color measurements before compression even runs.

Circle of confusion. The blur diameter a point is allowed to reach before a viewer calls it unsharp. It is a viewing assumption, conventionally the frame diagonal divided by 1500, not a property of your camera.

Codec. The scheme that encodes and decodes video. An all-intra codec encodes every frame independently, which is what you want for anything you created.

Color filter array. Filters over sensor photosites that sample different spectral bands. A Bayer pattern places green over half the sites and red and blue over a quarter each; demosaicing estimates the other channels. Other sensor arrangements exist.

Color reference chart. A card of printed patches of known color, photographed in the subject's light and plane, that lets an opposing expert re-derive your color correction from your own image.

Color temperature. A one-number description of a light's color. A light that is not a blackbody radiator has only a correlated color temperature, and two lights sharing one can still look plainly different.

Content credential. A cryptographically signed manifest binding capture information and actions to a file. It is evidence of where a file came from, never evidence that the scene was real.

Contrast sensitivity. The smallest luminance difference the eye can detect. It peaks near half a percent in daylight and around eight percent at night, a factor of sixteen.

Crop factor. The ratio of the full frame diagonal to your sensor's. It tells you how a lens frames, not what focal length it is, and every calculation uses the real focal length.

Cross-polarization. Filters on the lights and lens arranged to reduce specular reflection. Compare polarized and unpolarized frames when glare or color matters.

Culling. Selecting which frames go into the report. Culling by selection is a discipline; culling by deletion is a preservation problem.

Day-in-the-life film. A recording of a plaintiff's daily activities offered to show the impact of an injury. It raises objections about staging, self-serving behavior, cumulativeness, and its dominating effect.

Deinterlacing. Converting interlaced fields into progressive frames. Methods retain, interpolate, or combine information differently. Preserve the original and document the method chosen for the analysis.

Demosaicing. Reconstructing full color at every pixel from the single color each photosite measured. A raw file preserves the measured mosaic; a JPEG contains only the camera's one-time guess.

Depth of field. The range of subject distances that render acceptably sharp. It scales with the square of subject distance and inversely with the square of focal length, which is why macro work has millimeters of it.

Diffraction. Spreading of light at an aperture that can reduce resolved detail as the aperture closes. Evaluate it with magnification, pixel size, depth of field, and output requirements rather than a universal format cutoff.

Digital Negative. An archival container for raw data. It is not automatically lossless, and a file written by a neural denoising tool arrives in the same wrapper, so treat it as processed rather than original.

Distortion correction. Software or in-camera warping that straightens lens curvature. It is a geometric warp that resamples the image and changes the projection model, and many raw converters apply it on open.

Documentation image and examination quality image. The two published categories. Documentation images record appearance, condition, or location. Examination quality images are intended for scientific analysis and require a lossless format at the highest resolution.

Drop-frame timecode. A numbering scheme that skips labels so timecode approximates elapsed time at specified rates. The convention does not itself drop captured frames, but it does not prove the recording contains no missing frames.

Duplicate. Under the evidence rules, a counterpart produced by a process that accurately reproduces the original. Rule 1003 permits duplicates subject to its authenticity and fairness exceptions and other applicable evidentiary requirements.

Dynamic range. The span from the darkest usable signal to saturation, always measured against a chosen noise criterion. On one measured sensor the two published criteria give 12.37 stops and 9.00 stops.

Effective f-number. The working aperture at high magnification, equal to the marked f-number times one plus the magnification. At life size a marked f/16 is f/32.

Electronically stored information. The category the federal preservation rule reaches. Image files, raw files, video exports, and point clouds are all inside it; prints, negatives, and slides are not.

Emissivity. A surface's efficiency in emitting thermal radiation. Thermal temperature estimates require an appropriate emissivity value and assessment of reflected radiation and other measurement conditions, especially on shiny metal.

Error level analysis. A resave-and-subtract technique that highlights regions with different compression histories. Its own author says a bright region may only mean an Adobe product touched the file. Keep it out of your report.

Exposure value. A number combining aperture and exposure time. Scene-based values such as 15 for full sunlight are planning estimates; meter the actual scene.

Field. Half of an interlaced video frame, either the odd lines or the even lines, captured at a different instant from the other half. For timing analysis you want fields, not frames.

Focal length. The optical property that sets angle of view for a given sensor. The number printed on the barrel is nominal and is not a measurement, which is why metrology requires calibration.

Focus stacking. Merging frames shot at stepped focus distances into one image with extended depth. It is a computational composite: retain every source frame and label it as a stack in the report.

Foundation. Evidence supporting the proposed use of an exhibit. Photographs may be authenticated through witness knowledge, circumstantial evidence, process evidence, or other adequate methods.

Four cardinal points protocol. Photographing an impression with oblique light from twelve, three, six, and nine o'clock. It exists because a striation running along the light direction casts no shadow across itself.

Frame rate. How many frames a video records per second. Write it as a fraction, because the real rates are often 24000/1001, 30000/1001, and 60000/1001.

Global shutter. Capture with a common exposure interval across the sensor. It avoids row-timing distortion, but does not eliminate motion blur or every source of geometric error.

Gray card. A neutral card serving two separate purposes that practitioners conflate. Spectral neutrality is what matters for white balance; the 18 percent reflectance value is what matters for exposure.

Ground control point. A surveyed point of known position placed in a photogrammetric scene. A subset must be withheld from the solution and used only to measure residual error.

Ground sampling distance. The real-world size a single pixel covers. It is a statement of resolution, never of accuracy, and conflating the two is a cheap win for your opponent.

Group of pictures. The repeating structure of self-contained, predicted, and bidirectional frames in compressed video. Longer groups compress better and capture quick transitions less effectively.

Guide number. A flash's power expressed as f-number times distance. It means nothing without a stated sensitivity and a stated zoom head position, because narrowing the beam inflates it.

Hash. A fixed-length fingerprint computed from every bit of a file. Change one bit and the output changes completely. It is not encryption and you cannot recover the file from it.

High Efficiency Image File Format. A newer image format roughly twice as efficient as JPEG. Its damage does not show the tell-tale 8 by 8 grid; it smooths and substitutes detail, which looks clean.

Hyperfocal distance. The focus distance at which sharpness extends from half that distance out to infinity. A 35 millimeter lens at f/8 has a hyperfocal distance of 5.14 meters on full frame.

Illustrative aid. Under the new federal rule, any presentation offered not as evidence but to help the trier of fact understand evidence or argument. It stays out of the jury room absent consent or good cause.

Image metadata. The block of structured text a camera writes at capture, formally the Exchangeable Image File Format. It is unsigned, plaintext, writable by free software, and corroborative rather than conclusive.

Image stabilization. A system that counteracts camera shake, worth 2 to 5.5 stops. It does nothing at all about a subject that is moving.

Infrared imaging. Photography of reflected near infrared light, practically 700 to 900 nanometers. It carries no color data and should be converted to black and white after capture.

Interlacing. Recording alternate lines at alternate instants. A 1080i frame is not a frame; it is two fields captured 16.683 milliseconds apart at the common rate.

Intra frame. A video frame containing all newly encoded information, meaning a complete picture. Only these can be verified independently of the frames around them.

Inverse square law. Illumination falls as the square of distance from a point source. Doubling the distance costs exactly two stops, so a foreground at 1.5 meters and a background at 6 meters differ by four.

JPEG. The compressed format most cameras produce by default. The white balance is baked into the pixel values, the bit depth is 8, and the camera's interpretation cannot be re-made.

Litigation hold. Counsel's instruction to preserve material once litigation is anticipated. It reaches your cards, working drives, offsite copies, synced accounts, and email attachments.

Location tagging. Position and related fields stored with an image. Determine the location source, timing source, and uncertainty before treating them as an independent check on camera time.

Lossless and lossy compression. Lossless compression discards nothing. Lossy compression discards data permanently and may be acceptable for documentation images, but is not recommended for images that will be analyzed or compared.

Luminance. The brightness of a surface as seen from a viewpoint, measured in candelas per square meter. Cone vision carries above about 0.03 of those units; below it rods take over.

Macro lens. A lens that reaches life-size magnification, meaning the image on the sensor is as large as the object. Buy one by its working distance at maximum magnification, measured by you.

Microphone type and pattern. Condenser capsules are sensitive with extended high-frequency response; dynamic capsules are tougher and less sensitive. Directional patterns buy working distance: an omnidirectional scores 1.00, a hypercardioid 2.00.

Mosquito noise. Shimmering compression artifacts around edges. It is one of the artifacts the published compression guidance does not name, which is a gap worth stating in your report.

Motion blur. Smear from subject or camera movement during the exposure. Blur on the sensor equals subject speed times exposure time times magnification, and the numbers are worse than intuition suggests.

Native file. The file a recorder or camera wrote, in its own format, with its own timing and overlay. It sits at the top of the quality hierarchy, above an export and far above a screen recording.

Noise. Variation in recorded signal, including read noise and photon shot noise. Greater photon collection improves shot-noise-limited signal-to-noise ratio, while ISO behavior and processing require camera-specific assessment.

Normal lens. Conventionally a lens whose focal length equals the frame diagonal, 43.3 millimeters on full frame. It reproduces the geometry of central, attentive looking, not the field of human vision.

Oblique light. Light placed low enough to cast a shadow into the relief of a surface. The published standard states that criterion and prescribes no angle, because the correct angle depends on the depth of the relief.

Original and working copy. The original is an accurate and complete replica of what the camera wrote. Everything you process is a working copy, and processed output is derivative evidence with its own integrity requirements.

Overlap. The fraction of content shared between adjacent frames. Roughly a third for scene coverage; at least 75 percent frontal and 60 percent side for photogrammetry, rising to 90 percent on large vertical objects.

Painting with light. Building one exposure from multiple illuminations, with the lens covered between flashes where the procedure requires it. Check for stray light, operator visibility, and incomplete coverage.

Perspective compression. The flattening of apparent depth when you photograph from far away with a long lens. Perspective is caused by distance, not by the lens, but focal length dictates where you must stand.

Photogrammetry. Deriving measurements from photographs. Reported performance belongs to the tested capture and analysis conditions; validate the accuracy and uncertainty of the actual measurement.

Photo-response non-uniformity. The sensor fingerprint left by manufacturing variation in silicon. It has real scientific standing, needs hundreds of images to build a reference, and degrades under compression and cropping.

Photopic and scotopic vision. Cone-dominated and rod-dominated visual regimes. Night scenes can involve mesopic or photopic conditions as well as scotopic vision, depending on illumination and adaptation.

Pictorial testimony theory. Authentication through a knowledgeable witness who testifies that a photograph fairly and accurately portrays the scene. This is one available route, not an exclusive rule for self-made photographs.

Pixel pitch. The center-to-center spacing of photosites. Light gathering scales with its square, which is why a 6.00 micrometer full frame pixel gathers roughly 24 times the light of a 1.22 micrometer phone pixel.

Point cloud. The set of three-dimensional points a scanner or a photogrammetric solution produces. Archive it in the open interchange format specified by ASTM International standard E2807.

Preimage resistance and collision resistance. Preimage resistance concerns finding an input for a given hash; collision resistance concerns finding distinct inputs with the same hash. Integrity analysis also requires secure baseline records, provenance, and an assessment of the relevant attack scenario.

Presentation timestamp. The per-frame time value stored throughout a video container. Compute the difference between consecutive timestamps rather than trusting a nominal rate.

Quantization table. The divisor grid a compressor uses to decide what detail to discard. It is a written record of what the camera threw away, and every camera uses its own.

Raw file. A camera format that can preserve sensor data and interpretation parameters. Determine the actual format and processing. Preserve the original and disclose adjustments; raw format alone does not prove an image was unchanged.

Readout time. How long a rolling-shutter sensor takes to scan from top to bottom. Published oscilloscope measurements range from 3.7 milliseconds on a stacked body to about 71 milliseconds in a silent full-frame mode.

Reciprocal rule. Use a shutter speed numerically closest to the 35 millimeter equivalent focal length when handholding. It was derived for small prints, so double it for files that will be enlarged.

Registration. Aligning multiple scanner setups into one coordinate frame. It is a separate error budget that compounds across setups, and its statistics belong in the report.

Retroreflective material. Tape and sheeting that returns light toward its source. It ages measurably, so an exhibit shot against fresh tape is not an exhibit of the trailer as it existed.

Reverse projection photogrammetry. Re-photographing a scene with a reference of known height placed at the subject's position. It is not the same as scaling within a single image from objects of known size.

Ringing. Light and dark bands near a contrast edge caused by processing such as lossy compression. The bands can resemble physical lines, so compare originals and other views before identifying the feature.

Rod and cone. Photoreceptor classes with different sensitivity, temporal response, and color functions. Rod-mediated vision is achromatic; actual nighttime vision can involve both classes.

Rolling shutter. A sensor that reads out one row at a time from top to bottom, so every row in a frame has a different exposure start time. Vertical edges lean, and lengths along the scan direction stretch or compress.

Sample aspect ratio. The width-to-height ratio of a stored sample. Some surveillance formats require nonsquare-pixel display. Verify the intended ratio before measuring horizontal dimensions.

Scale. A rigid reference of known dimension placed in the plane of the evidence. The standard forensic pattern carries graduated legs, a tonal reference, and three circles used to detect and correct off-axis perspective.

Scrub. A scheduled pass in which a checksumming file system reads all stored data and repairs what it can from a replica. Recommended monthly or more often.

Sensor plane. The plane of the imaging chip. Held parallel to the subject plane, measurement is direct; tilted by 20 degrees, dimensions along the tilt read 6.0 percent short and shapes change.

Shutter angle. A cinema convention expressing exposure time as a fraction of the frame interval. The 180 degree convention gives one over twice the frame rate, and it is an aesthetic standard, not a measurement standard.

Silent witness theory. Authentication through evidence supporting a recording process when no witness supplies a direct account of the recorded event. Surveillance footage is not restricted to this route.

Simulation. A computation that draws its own conclusion from entered data. It is substantive proof and pulls the reliability rule and its case law onto your exhibit, whatever you called it in the report.

Skew. Apparent lean that can result from motion during rolling-shutter readout. Estimating readout time or speed requires the relevant motion geometry and other known parameters, not merely any vertical line.

Specular reflection. A directional reflection of a light source. It can obscure surface detail or clip channels if exposure exceeds capture capacity; neither outcome is inevitable.

Spoliation. Destruction, material alteration, or failure to preserve evidence where a preservation duty applies. Photographs can document condition but do not automatically discharge the duty to preserve the underlying item.

Stop. A factor of two in light. Aperture steps, shutter steps, and sensitivity steps are all interchangeable in this currency, which is what makes exposure arithmetic rather than guesswork.

Structure from motion. Recovering camera positions and a three-dimensional point set from overlapping photographs, by detecting features, matching them, solving poses in a bundle adjustment, and fusing depth.

Substantially similar conditions. The foundational showing required before a staged test or demonstration is admitted. The label you attach does not control; what controls is whether the demonstration looks close enough to the event to mislead.

Sunny 16. A field exposure rule needing no batteries: in direct sunlight, set f/16 and a shutter speed equal to the reciprocal of the sensitivity. It computes to exposure value 15, which is the published value for full sun.

Tagged Image File Format. An image container supporting several encodings, including uncompressed data. Use a documented archival variant and test readability over time; the format alone does not guarantee future access.

Terrestrial laser scanning. Sweeping a beam over a scene and recording range and angle for millions of points. Read the specification with its conditions: reflectance, confidence level, and single-shot measurement.

Thermal imaging. Recording long-wave radiation a subject emits, typically 7.5 to 13 micrometers. It is a different technology from infrared photography, glass is opaque to it, and it is not a temperature measurement without more work.

Three-two-one rule. Three copies, on two kinds of media, with one offsite. Its citation trail is weak, so defend it from published failure rates rather than from authority.

Timecode. A time label associated with video. Genlock synchronizes timing signals; jam sync sets a timecode reference. Measure and monitor subsequent drift rather than assuming a fixed result for every pair of devices.

Ultraviolet imaging. Photography of reflected ultraviolet radiation, in practice at 365 or 254 nanometers. Wavelengths below 280 nanometers denature deoxyribonucleic acid rapidly during exposure, which reorders your evidence handling.

Variable frame rate. A recording whose frames are not evenly spaced in time. Surveillance recorders shift rates on motion triggers, so counting frames and dividing by a nominal rate can be wrong by an enormous factor.

White balance. Three gain numbers applied to the red, green, and blue channels to make a scene look neutral. Three numbers cannot invert a spectrum, so white balance neutralizes a cast and does not restore missing reflectance.

Working distance. The clear space between the front of the lens and the subject, which is not the minimum focus distance printed on the specification sheet. It decides whether you can get a light in beside the subject.

Write blocker. A hardware device that physically prevents any modifying operation from reaching a protected storage device. Unlike a memory card's sliding tab, it does not depend on anyone's good behavior.

Write-once media. Storage that cannot be rewritten, whether a recordable optical disc or a cloud object under a compliance-mode lock. It turns "I did not alter the file" from testimony into a property of the system.

Appendix G. Standards, Rules, and Sources

Everything listed here appears in the chapters of this book. Nothing has been added from any other source. Where a chapter gave a citation in a particular form, that form is reproduced.

Federal Rules of Evidence Cited

• Federal Rule of Evidence 107, illustrative aids, effective December 1, 2024, subsections (a),

(b), (c), and (d), with the 2024 Committee Note.

• Federal Rule of Evidence 403, excluding relevant evidence for prejudice, confusion, waste of

time, or other reasons, enacted 1975 and restyled 2011.

• Federal Rule of Evidence 611(a), the source of the pedagogical device practice described in

United States v. Bray.

• Federal Rule of Evidence 702, testimony by expert witnesses, as amended effective December 1,

2023, subsections (c) and (d), with the 2023 Advisory Committee Note.

• Federal Rule of Evidence 901(a), the general authentication requirement.
• Federal Rule of Evidence 901(b)(1), testimony of a witness with knowledge.
• Federal Rule of Evidence 901(b)(4), distinctive characteristics and the like.
• Federal Rule of Evidence 901(b)(9), evidence about a process or system, with its Advisory

Committee Note.

• Federal Rule of Evidence 902(11) and 902(12), the certification requirements that 902(13) and

902(14) incorporate.

• Federal Rule of Evidence 902(13), records generated by an electronic process or system,

effective December 1, 2017.

• Federal Rule of Evidence 902(14), data copied from an electronic device, storage medium, or

file, with its Advisory Committee Note and that Note's limiting sentence.

• Federal Rule of Evidence 1001(c), defining a photograph as a photographic image or its

equivalent stored in any form.

• Federal Rule of Evidence 1001(e), defining a duplicate.
• Federal Rule of Evidence 1003, admissibility of duplicates.
• Federal Rule of Evidence 1006, summaries to prove content.

Federal Rules of Civil Procedure Cited

• Federal Rule of Civil Procedure 26(a)(2)(B), the written report requirement, including

subparagraphs (i), (ii), and (iii), with the 2010 Advisory Committee Note.

• Federal Rule of Civil Procedure 26(b)(1), relevance and proportionality.
• Federal Rule of Civil Procedure 26(b)(3)(A) and (B), work product, as incorporated by

26(b)(4)(B).

• Federal Rule of Civil Procedure 26(b)(4)(B), draft report protection.
• Federal Rule of Civil Procedure 26(b)(4)(C), attorney and expert communications, with its three

carve-outs.

• Federal Rule of Civil Procedure 26(b)(4)(D), the non-testifying consultant.
• Federal Rule of Civil Procedure 26(b)(4)(E), fees for time spent responding to discovery.
• Federal Rule of Civil Procedure 26(c)(1) and 26(c)(1)(E), protective orders and designating who

may be present.

• Federal Rule of Civil Procedure 34(a)(2), entry onto land for inspection, which expressly

enumerates photographing.

• Federal Rule of Civil Procedure 34(c), the bridge to non-party inspection.
• Federal Rule of Civil Procedure 37(e), failure to preserve electronically stored information,

subsections (1) and (2), with the 2015 Advisory Committee Note.

• Federal Rule of Civil Procedure 45, non-party subpoenas, including 45(a)(1)(A)(iii) and

45(d)(2)(A), with the power dating to the 1991 amendments.

Federal Rule of Criminal Procedure Cited

• Federal Rule of Criminal Procedure 53, cited in Chapter 35 only to correct its misuse: it is a

criminal rule barring photographing in the courtroom during judicial proceedings, and it does not by its own force govern civil proceedings, hallways, lobbies, or the building exterior.

Cases Cited, Alphabetically

• Bannister v. Town of Noble, Oklahoma, 812 F.2d 1265 (10th Cir. 1987)
• Barnes v. General Motors Corp., 547 F.2d 275 (5th Cir. 1977)
• Baugh ex rel. Baugh v. Cuprum S.A. de C.V., No. 12-2019 (7th Cir. Sept. 13, 2013)
• Becker v. Computer Sciences Corp., 541 F. Supp. 694 (S.D. Tex. 1982)
• Belcher v. Bassett Furniture Industries, Inc., 588 F.2d 904 (4th Cir. 1978)
• Bergner v. State, 397 N.E.2d 1012 (Ind. Ct. App. 1979)
• Bolstridge v. Central Maine Power Co., 621 F. Supp. 1202 (D. Me. 1985)
• Branzburg v. Hayes, 408 U.S. 665 (1972)
• Bray v. Bi-State Development Corp., 949 S.W.2d 93 (Mo. App. E.D. 1997)
• California v. Ciraolo, 476 U.S. 207 (1986)
• Chandler v. Florida, 449 U.S. 560 (1981)
• Chapman ex rel. Estate of Chapman v. Bernard's, Inc., 167 F. Supp. 2d 406 (D. Mass. 2001)
• Commonwealth v. Serge, No. 150 MAP 2004, decided April 26, 2006, affirming the Superior Court

decision reported at 837 A.2d 1255 (Pa. Super. 2003)

• Datskow v. Teledyne Continental Motors, 826 F. Supp. 677 (W.D.N.Y. 1993)
• Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993)
• Dow Chemical Co. v. United States, 476 U.S. 227 (1986)
• Florida v. Riley, 488 U.S. 445 (1989)
• Food Lion, Inc. v. Capital Cities/ABC, Inc., 194 F.3d 505 (4th Cir. 1999)
• Foster v. Crawford Shipping Co., 496 F.2d 788 (3d Cir. 1974)
• Four Corners Helicopters, Inc. v. Turbomeca, S.A., 979 F.2d 1434 (10th Cir. 1992)
• Fusco v. General Motors Corp., 11 F.3d 259 (1st Cir. 1993)
• General Electric Co. v. Joiner, 522 U.S. 136 (1997)
• Gladhill v. General Motors Corp., 743 F.2d 1049 (4th Cir. 1984)
• Griffin v. State, decided by Maryland's high court on April 28, 2011
• Grimes v. Employers Mutual Liability Insurance Co. of Wisconsin, 73 F.R.D. 607 (D. Alaska 1977)
• Haley v. Byers Transportation Co., 414 S.W.2d 777 (Mo. 1967)
• Hall v. General Motors Corp., 647 F.2d 175 (D.C. Cir. 1980)
• Hinkle v. City of Clarksburg, 81 F.3d 416 (4th Cir. 1996)
• Houchins v. KQED, Inc., 438 U.S. 1 (1978)
• Jackson v. Fletcher, 647 F.2d 1020 (10th Cir. 1981)
• Jenkins v. Associated Transport, Inc., 330 F.2d 706 (6th Cir. 1964)
• Kearney v. Salomon Smith Barney, Inc., 39 Cal. 4th 95 (2006)
• Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999)
• Kyllo v. United States, 533 U.S. 27 (2001)
• Long Lake Township v. Maxon, decided by the Michigan Supreme Court on May 3, 2024
• Lorraine v. Markel American Insurance Co., 241 F.R.D. 534 (D. Md. 2007)
• National Press Photographers Association v. McCraw, 90 F.4th 770 (5th Cir. 2024)
• New York State Association for Retarded Children, Inc. v. Carey, 706 F.2d 956 (2d Cir. 1983)
• Pell v. Procunier, 417 U.S. 817 (1974)
• People v. Cauley, 32 P.3d 602 (Colo. App. 2001)
• Pierce v. Ramsey Winch Co., 753 F.2d 416 (5th Cir. 1985)
• Project Veritas v. Schmidt, No. 22-35271 (9th Cir. Jan. 7, 2025) (en banc)
• Randall v. Warnaco, Inc., 677 F.2d 1226 (8th Cir. 1982)
• Residential Funding Corp. v. DeGeorge Financial Corp., 306 F.3d 99 (2d Cir. 2002), named in the

2015 Advisory Committee Note as a line of cases the rule rejects

• Robinson v. Missouri Pacific Railroad, 16 F.3d 1083 (10th Cir. 1994)
• Sanchez v. Denver & Rio Grande Western Railroad Co., 538 F.2d 304 (10th Cir. 1976)
• Silvestri v. General Motors Corp., 271 F.3d 583 (4th Cir. 2001)
• State v. Matthews, 479 Md. 278, 277 A.3d 991 (2022)
• Swajian v. General Motors Corp., 916 F.2d 31 (1st Cir. 1990)
• Thomas v. C.G. Tate Construction Co., 465 F. Supp. 566 (D.S.C. 1979)
• United States v. Bray, 139 F.3d 1104 (6th Cir. 1998)
• United States v. Causby, 328 U.S. 256 (1946)
• United States v. Janati, 374 F.3d 263 (4th Cir. 2004)
• United States v. Johnson, 114 F.3d 808 (8th Cir. 1997)
• United States v. Kyler, 429 F. App'x 828 (11th Cir. 2011)
• United States v. Quinn, 18 F.3d 1461 (9th Cir. 1994)
• United States v. Rembert, 863 F.2d 1023 (D.C. Cir. 1988)
• United States v. Stearns, 550 F.2d 1167 (9th Cir. 1977)
• United States v. Taylor, 530 F.2d 639 (5th Cir. 1976)
• United States v. Wood, 943 F.2d 1048 (9th Cir. 1991)

Standards Bodies and Their Documents

Scientific Working Group on Digital Evidence. The live body in this field. It publishes free versioned documents and maintains photography, imaging, and video committees. Documents named in this book:

• Image Processing Guidelines, document 15-M-002
• Guidelines for Low Light Crime Scene Photography
• Lighting Techniques
• Guidelines for the Use of Reflected Ultraviolet Radiation in Forensic Photography, document

19-P-001

• The companion reflected infrared document, 19-P-002
• Guidelines for Digital Imaging of Footwear and Tire Impressions, document 17-P-003, version 2.0
• Image categories in forensic science, 2025
• Best practices for maintaining the integrity of imagery, current as of March 3, 2025
• Best practices for image authentication, version 2.0, March 3, 2025
• Compression and file format guidelines
• Best Practices for the Forensic Use of Photogrammetry, version 1.2
• Technical Overview of Digital Video Files, document 17-V-001
• Best Practices for Data Acquisition from Digital Video Recorders, document 17-V-002
• Considerations for the Use of Time-Based Analysis of Digital Video for Court, document 19-V-003
• Best Practice for Frame Timing Analysis of Video Stored in ISO Base Media File Formats, document

19-V-005, version 1.1

• Core Technical Concepts for Time-Based Analysis of Digital Video Files
• Position on hashing algorithms, September 29, 2019
• Collection best practice, published November 20, 2025
• Committee guidance on technical aspects of digital cameras, photographic equipment

recommendations, macro photography, evidence photography in a controlled setting, and forensic image analysis

Scientific Working Group on Imaging Technology. Defunct. Cite it for foundational principles only, with its date attached, and note that its old web address no longer belongs to it.

• Section 1, overview, version 3.3, dated June 11, 2010
• Section 11, documenting image enhancement, and its four operative principles
• Impression photography guidance, the source of the overall, midrange, and close-up sequence
• Guidance listing cropping alongside brightness and contrast adjustment as image processing