Digital Photos Challenged In Court
from the whatcha-been-manipulating? dept
While some police departments have been thinking of moving to digital photography for recording crime scene evidence, some court cases challenging the validity of digital photographs are making them think twice. Even though film camera photos can be manipulated as well, defense attorneys are ready and willing to challenge any digital photo with a simple demonstration of how easy it is to change and manipulate a photo in Photoshop. Some police departments are trying to figure out a way to have cameras take photos that are then “locked” so that there’s always the original photo to compare against any “adjusted” photos.
Comments on “Digital Photos Challenged In Court”
chain of evidence
I can’t think of any way to lock or sign a digital photograph that couldn’t be trivially overcome by the person in possession of the signing device, ie. the law enforcement agency.
And for that matter, film photographs have always been just as malleable. They can be cropped or manipulated in lots of ways, and even if they’re not, who’s to say that the photo wasn’t staged?
All evidence is ultimately based on trust in the personnel gathering and evaluating it. Fibers, DNA samples and test tubes can all be planted, switched or manipulated by incompetent or overzealous investigators. In fact, I remember recently reading about a fairly high-profile crime lab technician that was found to be doing these sorts of things at the prompting of the police dept.
And don’t even get me started on the scientific validity of fingerprint matching or the polygraph. (Hint: they’re not.)
In the end, in must be understood that, for all types of evidence, the trust isn’t placed in a medium or technique, but in a person. It’s the credibility of the people that makes a strong chain of evidence.
Re: chain of evidence
Film photographs can be scanned into Photoshop and manipulated before printing, but at least with film you always have the film negative which acts as the “locked” original version.
digital signatures
Assign an id number to each photo, take a digital signature of the photo and have it stored by some third party along with the id. Better yet, have the id and signature made public so that various organizations can regularly retrieve copies, to reduce the chance of a police department colluding with a single organization in modifying a signature.
No Subject Given
Canon already offers a ‘forensics’ kit which will sign photographs while it’s on the memory card. I think the next step would be to include a more rigorous PKI mechanism in the firmware: if a public key is on the memory card, sign or encrypt the image with it.
However, one more wrinkle: people have successfully hacked the $900 Canon 300D camera firmware to include most of the features found in its $1500 Canon 10D body. The Canon cameras essentially run a firmware version of 16bit MS-DOS, and the firmware is just a plain x86 executable file that interacts with proprietary data processing hardware.
Of course, that would be much more difficult if the Canon firmware had to be PKI signed properly…
We need more “cradle-to-grave” data security mechanisms in plain
Another red herring
The key standard for admitting (technically authenticating; other general admissibility rules apply) photographs and similar items (e.g., drawings or sketches) into evidence is “does the photo reasonably represent the [location, person, etc.] at the relevant time and date?” So when some jerk runs a stop sign and hits you, this rule allows you to take a picture of the stop sign after the accident, rather than before, which would normally be impossible.
We’ve always used verbal testimony to bridge the gap between the picture and other physical evidence (as the prior poster notes). Showing that things could be faked doesn’t do anything to besmirch the witness’ actual testimony, except in the eyes of conspiracy nuts and people looking to let someone popular off the hook.
VeriPic
VeriPic has a solution that has been in use for years. Even though courts are not challenging photos as much lately, their software can identify if a photo has been tampered with.