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Authenticating Digital Photographs as Evidence: A Practice Approach Using JPEG Metadata

by Joe Kashi

June 2006

When I first contemplated this article, the issue of authenticating digital photographs for evidentiary purposes seemed fraught with arcane complexity and uncertainty. However, that’s not actually true in practice. In fact, the metadata stored in any JPEG or RAW photographic file may help you authenticate that photograph and contradict the popular view that digital photographs can be easily and undetectably altered. Certainly, it is harder to undetectably fake a print made from a film negative than a digital file, but current digital cameras contain enough non-evident metadata to detect most alterations.

In this article, I will discuss some general evidentiary issues that arise when a party wishes to use photographic evidence, propose a standard procedure to ease the authentication of your own digital photographic evidence and offer a test as to whether or not you are receiving discovery of authentic photographic evidence from the other side. Surprisingly, this may be as easy to do with digital photographs as with photographic prints made from film negatives.

Photographic Authentication and Admissibility: Evidence Rules 901 and 1001

Under Evidence Rule 901 and its state analogues, photographs are typically admitted as demonstrative evidence to illustrate testimony. When used purely as demonstrative evidence, legal issues regarding authentication and chain of custody are somewhat relaxed so long as a competent witness can testify that the photograph fairly and accurately depicts the scene about which he or she is testifying. In these situations, it is generally not necessary that the authenticating witness be the same as the photographer or as a competent person who observed the making of the photograph. United States v. Clayton, 643 F.2d 1071, 1074 (C.A. 5, 1981. Videos are typically authenticated in the same manner as a still photograph. Saturn Manufacturing, Inc. V. Williams Patent Crusher and Pulverizer Company, 713 F.2d 1347, 1357 (C.A. 8, 1983). I will illustrate some portions of this discussion using a series of decisions by the Alaska Supreme Court whose evidentiary rules and interpretations typically closely follow majority federal views.

Under Evidence Rules 1001 through 1004, an “original” document (including a photograph) is required to prove the truth of the facts for which any document is offered. However, over many years, the definition of an “original” has been greatly expanded, particularly with regard to electronically stored information, and the requirement for an “original” is honored more in the breach than to the letter. Indeed, duplicates, including electronically made prints or digitally identical electronic file duplicates, are typically admissible to the same degree as an original document unless admitting the duplicate would prove inaccurate or unfair.

Authentication requirements are somewhat stiffened where there is a strong argument that a photograph does not accurately reflect the scene or that the use of a duplicate is inaccurate or unfair. Generally, a trial court’s admission or exclusion of proffered photographs is reviewed under an abuse of discretion standard. (See End Notes 2 and 4, below) Common sense, a reasonably objective evaluation of your intended use of the proposed photographic evidence and some trial experience are usually an adequate guide to the allowable demonstrative or evidentiary uses of a photograph. A trier of fact’s evaluation of “non-demeanor” evidence like photographs (as contrasted with live witness testimony) is theoretically subject to a less deferential standard of appellate review but this more stringent approach is often not strictly applied. (See End Note 5, below). However, when photographs are to be used as the basis for expert witness testimony or to actually prove the existence of an allegedly depicted condition, then they will be held to a higher standard and you will need to be much more cognizant of subtle technical and photographic parameters.

Admissibility of photographs varies, depending upon the evidentiary context and the purpose for which a photograph is offered

Courts are usually willing to tolerate some inaccuracies in a photograph so long as these are explained to the trier of fact so that they may be taken into account. However, where a photograph is used as a basis for establishing critical ultimate facts or as the basis for expert testimony, courts are less willing to overlook major gaps. For example, the Alaska Supreme Court, in Kaps Transport, Inc. v. Henry, 572 P.2d 72 (Alaska, 1977) stated, at 572 P.2d 75-76, the majority rule:

"That there are inaccuracies or defects in the photograph does not necessarily render it inadmissible as long as there is an explanation of these imperfections so that the jury is not misled", quoting Riksem v. Hollister, 96 Idaho 15, 523 P.2d 1361 (1974) and Southeastern Engineering & Mfg. Co. v. Lyda, 100 Ga.App. 208, 110 S.E.2d 550 (1959).

However, in Kaps, the Alaska Supreme Court excluded the photograph in question because the defendant’s accident reconstruction expert was attempting to use the photograph, in conjunction with a reconstructive technique known as perspective analysis, to establish how far across the highway centerline the Plaintiff had alleged strayed. In order to use a photograph as a basis for perspective analysis reconstruction, the focal length used to take the photograph and the conditions under which the photograph was taken must be known with a substantial degree of precision, which the Defendant could not show. In this case, the photograph was to be used to provide actual data about the accident scene rather than merely illustrating the area. Hence, it was subject to a more rigorous authentication process which it ultimately failed.

Similarly, where a photograph is offered to prove that some condition did not exist, a court will look closely at the time frame when a photograph was purportedly taken but still use a common sense case by case analysis. For example, if a photograph is offered of a criminal defendant’s hands purporting to show that there was no gunshot residue, and then the offering party must establish that the photograph was taken at a time when gunshot residue would still be apparent. Absent that showing, the photograph may not be admitted. On the other hand, where direct evidence of a condition provided by an otherwise authenticated photograph is only one link in a logical fact structure, the photograph will likely be admitted to prove the depicted condition.

In cases where there is sufficient countervailing testimony, the admission of photographs with a shaky time frame may be harmless error. For example, the Alaska Supreme Court refused to reverse a verdict despite the trial court’s admission into evidence of the defendant highway department’s arguably inaccurate photographs that purported to show that an accident site was well-sanded despite the Plaintiff’s contrary contentions. The time frame when these photographs were taken, relative to the time of the accident, was never precisely established but was sufficient contrary testimonial evidence by the investigating State Troopers actually at the accident establishing that photographs were inaccurate and that the road was poorly sanded. Hence, admitting these allegedly misleading photographs with an imprecise time frame was harmless error.

Metadata and Discovery

The proposed amendments to Civil Rules 26 and 34 effective as of December 2006 further broaden the definition of what constitutes an “original” document and expand both the discovery and usefulness of documents whose original format is electronically stored information (ESI). Indeed, the proposed new discovery amendments seem to require, as a default position, that any discoverable ESI be produced upon request in its “native format,” i.e., production of Microsoft Word documents should include identical copies of the original .doc format files, production of photographic documents should include digitally identical copies of the original JPEG format files, etc.

It appears that the new federal rules will also generally require the production of an electronic file's "metadata," that is, the electronic file’s internally stored information about the creation and alteration of any electronic file. Although privilege reviews will become more complex when you must produce metadata, the production of document metadata may be the most readily available, although not entirely fool-proof, means of determining the authenticity or alteration of electronically stored photographs. Most native format files, including the JPEG photographic files made by most modern digital cameras, will include the document’s metadata unless it is rather obviously stripped out with one of the numerous metadata removal programs now on the market.

I suggest that removing metadata from photographic files produced by non-attorneys and by expert witnesses is inappropriate in most instances except when there are obvious privilege issues. Consider, for example, how untrustworthy a photograph would be if the internal metadata showing the camera model, focal length and original date/time stamp is later removed. Concerns about its accuracy and authenticity would be very high, particularly if the metadata would have shown use of a camera that the witness did not own or that the photograph was taken on date or time remote from the pertinent time frame. On the other hand, if you know how to use a photographic file’s metadata, then you can use it to authenticate your own photographs for evidentiary purposes and possibly impeach the other party’s exhibits.

Here is how I suggest that a trial lawyer take advantage of these changes in the Civil Rules that provide for the discovery of both metadata and also native file format.

Some Authentication Procedures for Digital Photographs

Screenshots

Roll your mouse over any thumbnail to see a larger image.

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  1. Use a modern digital camera that conforms to the current EXIF 2.2 JPEG standard - most modern digital cameras store photographs in this file format. EXIF 2.2 JPEG stores a wealth of metadata that can help you authenticate and use digital photographs.

  2. Use the digital camera's setup menu to set the camera for normal sharpness, contrast, and color saturation. When feasible, try to use a zoom setting that renders the scene's optical perspective equivalent to how it would be seen by the human eye. See End Note 1, below. This is relatively objective data will be recorded in the JPEG metadata and will either help you authenticate your digital photos or render them suspect in the case of non-standard settings.

  3. Cameras do not always expose scenes perfectly, especially under non-standard lighting conditions. In order to minimize ANY authentication challenges based upon alleged later digital alteration with a computer program, I suggest that whenever possible you use either the exposure bracketing feature found in better digital cameras or the RAW file format found in many higher end cameras.

  4. Bracketing means that the camera will take three differently exposed shots of the same scene, one shot at the calculated best exposure, one with less than calculated exposure, and one with more exposure. Adjust the camera’s setup to provide for a 0.7 EV value between each bracketed exposure. One of these JPEG shots should be quite usable without the need for any computer enhancement for brightness, contrast or sharpness.

  5. RAW format photographic files are easier to enhance and often provide a better final result with the concomitant benefit of being able to more easily revert the original RAW file back to exactly the default as taken by the camera. Most cameras that include a RAW file option also make a JPEG file of the shot at the same time, which is very helpful for authentication. However, you will not be able to use exposure bracketing, which is probably the best way to deal with authentication challenges.

  6. Make reference files for each photograph that you may use later. Do not modify any reference files, ever. Make any corrections to an exact copy. Use JPEG 2.2 metadata to your advantage to authenticate your photos by always retaining the original JPEG in an unmodified state exactly as it came from the camera.

  7. Use a digital signature to lock the original unaltered reference file exactly as it came from the camera to avoid allegations of potential tampering. Digitally sign a photograph as promptly as possible.

  8. Be aware that almost all digital cameras sequentially number each photograph and producing only the best of the bracketed images will result in gaps that may cause some questions that you will probably need to explain. Of course, if you or your office staff took the photographs, then any photographs are likely protected by the work-product privilege until you disclose them.

  9. Learn how to view the metadata in a EXIF 2.2 JPEG file. The newer 2.2 version of EXIF includes date of exposure, focal length, exposure data, etc, the total of which is quite enough to authenticate photographs in most instances. You probably didn’t even know that this data exists in modern JPEG photographic files but you can easily view it using the File, file info, commands contained in Adobe Photoshop CS2 and in Photoshop’s lower end “lite” version, Adobe Photoshop Elements 4.0. See the attached screen prints 1, 2, 3 and 4 that show available inherent metadata and optional user metadata input. Note you can track a photograph’s history in these screens. Screen 4 shows a portion of the “advanced” EXIF metadata display, which includes quite a number of items. Under PDF properties, you will find not only the “creation date” but also the most recent “modification date”.

  10. Sony's RAW file conversion program, and probably RAW file programs provided with other high-end cameras, will display a surprising amount of metadata for RAW format photographs simply by moving your mouse cursor over a photo’s thumbnail view in a folder window. See attached screen print 5. In fact, even with basic JPEG files, moving the mouse cursor over a JPEG thumbnail will display metadata showing the camera with which the picture was taken, the size of the picture in pixels, and the date that the picture was taken. See screen shot 6.

  11. As soon as possible after taking a photograph, use Photoshop CS2 or Elements 4.0, to add optional metadata documenting where the photograph was taken, by whom, etc. This will also help you sort out photographs by category later. Do this only to an exact copy because adding the optional metadata will show as a modification to the photograph in its basic metadata. Digitally sign and also retain this documentation file in an otherwise unaltered state.

  12. Note that the advanced metadata shown in Photoshop CS2 and in Elements 4.0 also show whether the photograph was subject to any non-standard saturation, contrast or sharpness modification by the camera when the picture was taken. The equivalent focal length to which the zoom lens was set when the picture was taken will also be retained, which can be useful if there are challenges to the accuracy of the photograph’s optical perspective. (For more information on this point, see End Note 1.)

  13. It will sometimes be necessary to enhance photos that are underexposed or to sharpen latent detail using the standard functions of a generally used program like Photoshop CS2 or Photoshop Elements 4.0. However, avoid any excess processing or any functions that alter, hide or enhance only part of a photo. Examples of partial alteration include the clone stamp tool that is often used in art photos to replicate part of an image in another part of a photograph or to blot out some details. While these tools may be useful for art gallery photos that look great except for the power line that’s unfortunately in the way, they have no place in the courtroom in almost any conceivable circumstances.

  14. You can use these same procedures in reverse to determine whether the other side’s photographs can be properly authenticated. A disclosed photo’s metadata may also provide clues that, in conjunction with other information, may or may not support authentication of a photograph. Does the person purporting to take the photograph know what sort of camera was used and do they have access to the actual camera? The EXIF 2.2 metadata will show the camera model actually used to take the photo. Does the photograph match what would be expected under the given lighting conditions, taking into account the camera data embedded in the EXIF 2.2 metadata.

  15. What does the picture itself show? Some of the screen shots that I have included here depict unusual circumstances, a low level volcanic eruption of Cook Inlet’s Mt. Augustine on an unusually clear evening with at least 70 miles visibility. Granted that this is an extreme case to show a point, but if it was sufficiently important, you could check governmental weather and geological data to see whether reported weather and volcanic conditions on a particular date are consistent with what’s purportedly shown on a photograph. Cross-checking accident site photographs would be a more mundane example of the same principle. As another example, consider the boiler corrosion photographs at issue in the case discussion in End Note 4, below. If the apparent contrast, color saturation, and color balance of any exhibits seem incongruent with the camera settings contained in the metadata, then you may have an argument that these exhibits unfairly and inaccurately depict a condition and should be excluded.

Endnotes


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About the Author

Joe Kashi is an attorney and litigator living in Soldotna, Alaska, who is active in the Law Practice Management Section and a technology editor for Law Practice Today. He has written regularly on legal technology for the Law Practice Management Section, Law Office Computing magazine and other publications since 1990. He received his B.S. and M.S. degrees from MIT in 1973 and his J.D. from Georgetown University in 1976, and is admitted to practice in Alaska, Pennsylvania, the Ninth Circuit, and the U.S. Supreme Court.