By Joe Kashi, for the Redoubt Reporter
Way back in 2013, (well, a few weeks ago in our Dec. 11, 2013 issue), we considered why digital photography and videography might be persuasive legal evidence. This week, let’s look at some factors affecting the credibility and usability of digital imagery in a legal setting.
When digital images first became common, authenticating and using these images for legal purposes seemed uncertain due to the perception that they might be impermissibly but undetectably altered. We’ve found, however, that that’s hardly ever a problem in practice. We’re still reliant on the traditional live witness stating under oath that photos accurately represent the photographed situation. From a more technical perspective, the metadata stored in every JPEG or RAW photographic file can often be used to authenticate a photograph, or at least provide a good deal of information about how, when and where a photo was taken.
At a more rarified level, forensic software techniques developed for the FBI at Dartmouth College and State University of New York add a much higher level of certainty where serious expert analysis and testimony are needed. It’s only a matter of time until that sort of forensic software becomes readily available at commercially reasonable prices.
Some general evidence issues arise whenever a party wishes to authenticate and use any photographic evidence, digital or otherwise. Surprisingly, authenticating digital images might be as reliable as with traditional photographs from film negatives, at least when you have the original, unaltered digital file. Remember that any paper photo print, whether made from a film negative or digital camera image file, is more difficult to unimpeachably authenticate if you don’t have the camera’s original negative or unmodified digital imagery files.
I believe that RAW image files processed with a nondestructive program, such as Lightroom, are more reliable and easily authenticated in a legal setting. Images processed in PhotoShop are more suspect from a practical and technical standpoint. Everyone has heard the term “PhotoShopped” as a synonym for an excessively manipulated and altered photograph. However, when you’ve processed legal image files in Lightroom, you can always preserve an audit trail and revert an RAW image to exactly as it came out of the camera. That enhances its credibility.
Metadata is a general term for the data contained in every digital document that describes the document itself. A word processing document or email contains metadata about when the document was created and altered, and by whom. Photographic image files contain a great deal more metadata that’s sometimes termed EXIF data, automatically saved as part of the image file.
Photographic image metadata includes the lens focal length and/or a zoom lens’ magnification setting, color balance settings, the lens aperture/shutter speed settings and many other camera functions. Such information can very useful to the court when deciding the evidentiary value of a photograph. As a practical matter, only date and time metadata information can be easily and undetectably set to a false value by an untrained person.
In order to make photo prints that are actually useful as evidence, we need to make paper prints, prints large enough to be easily seen across a large room. That requires opening every image file in a photo program and then printing it. The simple act of importing an image file into a program and then opening and printing that file unavoidably alters the file, but basic operations like this are entirely proper and necessary. It’s entirely reasonable to use a “post-processing” program, such as Lightroom, to make routine corrections to basic exposure, picture contrast and shadow/highlight detail so long as this is disclosed to the court and the original, unaltered digital photo file is available upon request. Save the original camera memory card and lock it to prevent file deletion or overwriting.
If you do use JPEG files for legal purposes, and that’s less desirable, be careful about excessively compressing JPEG files when you save them. That often results in the creation of artificial details (“artifacts”) as well as the irretrievable loss of potentially critical fine details. I’ve seen this occur even with sophisticated clients. Hard disk and flash disk storage is cheap so there is no reason to intentionally compress JPEG files. You’ll lose fine detail that might later become crucial.
Make working copies of every file. Be sure to first save an unaltered archive copy of every imaging file before you open, process and print the working copy.
Also be careful about making large “corrections” to color balance when processing a photograph. Although inaccurate color balance often occurs for purely innocent technical reasons, changing the original image’s color balance can result in highly misleading and possibly inadmissible photographic “evidence.”
For example, if a photograph of a patch of asphalt pavement where a slip occurred appears medium brown, then that suggests that the pavement was dry and that there was no black ice. A darker, more neutral gray image suggests that there was at least some black ice when the photo was taken. One Alaska Supreme Court decision allowed a court to rely on a photo showing the approximate discoloration of furnace pipes to help prove that the pipes had corroded and released carbon monoxide into the family’s home.
Other factors affecting the accuracy and credibility of photographs include perspective and the focal length used to take the image, any lens distortion and the relative time frame when the photos or videos were made. Be sure that you bracket the exposure of every important shot to ensure at least one good exposure of each image. Avoid slow shutter speeds that blur details.
In past columns, we’ve discussed how different optical magnifications, such as wide-angle and telephoto lenses, optically affect perceptions of depth, size and relative position. To avoid later problems with optical distortion, I find that it’s a good idea to take each important photograph with a wide range of focal length magnifications. First, make wide-angle shots of the overall scene and then detailed shots with short telephoto magnifications that more accurately reflect how the human eye perceives the smaller areas upon which it focuses sharply. Have a person of known height or some other object of known size in an important area of an image in order to establish scale and size.
Some inaccuracies in a photograph may be tolerable if they’re adequately explained so that they may be taken into account. However, where a photograph is used as a basis for inferring critical ultimate facts or as the basis for expert testimony, courts are less willing to overlook major or unexplained technical deficiencies.
Have enough basic photo knowledge to avoid obvious technical defects. Remember, the more you need to explain away, the deeper your hole.
Local attorney Joe Kashi received his bachelor’s and master’s degrees from MIT and his law degree from Georgetown University. Many of his technology and photography articles can be accessed through his website, http://www.kashilaw.com.