Submitting Video Evidence In Court - Which File Format?

Watermarking of video files can almost always be applied to a particular VMS's database exports which are generally viewed only in their native Viewer (i.e. the file format is proprietary - it can't be viewed in WMP or VLC).

This watermarking of native files is almost always sold as the preferred method of exporting files, especially as part of a 'chain of evidence' scheme designed to retain data validity when the video is used as evidence in court. The claim I've heard against .AVI is that it can be challenged.

My question is this: Has anyone ever had a defense lawyer (or anyone else) successfully challenge the validity of video in an .AVI file format when submitted as evidence?

I get that technically someone with skills could edit an .AVI file, but do defense lawyers even understand the technology involved to challenge the format - and has it ever happened?


See interview with forensic analyst Grant Fredericks. Applied to both AVI and watermarking, money quote:

"Watermarking means nothing," said Fredericks. "Manufacturers who claim their stuff is admissible [because of watermarking] are not being honest. Using forensic tools we can extract the native files without ever having to go through watermarking or the encryption process. Watermarking really doesn't mean a thing to us."

Defense attorneys can and often object to the authenticity of manufacturer watermarking, even if it is digital. Video forensic experts typically analyze the details of the video as well as examining visible signs that would indicate tampering. Ultimately, this is the strongest way to validate the authenticity of the video, not a manufacturer watermark.

Using forensic tools we can extract the native files without ever having to go through watermarking or the encryption process...

Apoarently Grant has never heard of camera-side digital watermarking...

Watermarking really doesn't mean a thing to us. Defense attorneys can and often object to the authenticity of manufacturer watermarking, even if it is digital

It doesn't mean anything to Grant, but does it mean anything to the court? At first blush one might be tempted to say no, since he claims defense attorneys are objecting all the time (and presumably prevailing some of the time) to watermarking. But if defense attorneys often object, then it means that prosecutors attempt to use it even more often. And why would they even try unless it was of some value?

But I agree with Marty's unspoken skepticism on whether there really are these legal watermark wranglings taking place, I can't find any actual cases. In fact it sounds a little like the puported dummy camera liability court judgements.

And let's not forget that Grant has a vested interest in suggesting that the only way to be know for sure is having "the best Video forensic experts analyze the details of the video as well as examining visible signs that would indicate tampering".

And I agree with Undisclosed A, from the cases I did find that video eveidence is not excluded based on type, format or resolution, and certainly not on lack of watermark...

Rukmini, thanks for sharing Tredess Camera Watermarking. I've seen it before because it is on the Axis camera application list.

However, we've never heard of anyone using it and when we tried to get information from them, we got no response.

It could be potentially useful for super secure applications but it's certainly not widely used.

IANAL, but I've spoken to a few about this.

There seem to be a lot of myths about video evidence.

Practically any video can be admitted as evidence. This doesn't mean it will get you much, but it's admissable. It doesn't need to be 30fps, or watermarked, or a certain resolution, or in color, or anything.

Almost anything admitted by one side is going to be challenged by the other side. There can be a lot of "interpretation" about this, depending on the overall circumstances.

The neccessity for the video evidence to meet any criteria seems to often be related to how key/unique that video is to the overall position of one side or the other. If all you have is a video clip, you're probably going to want it to be a clean hi-res shot. If you have 30 pieces of evidence and the video just reinforces some key points or a general timeline, it's less important that it's of high caliber.

What stops someone from taking the video, editing it, then running it back through say an AXIS encoder, even using the technology mentioned above, and picking up a new watermark?

Chris, that's pretty devious!

My understanding is that such edits can be picked up / detected by a forensic video analysis. That's a reason why if the evidence is very critical but contentious that they would have an external expert analyze it.

Hopefully fear of prison. Re-watermarking video does not erase previous watermarks, rather it would provide a trail of such actions that the software would display, even without Grant being called.

Though similar attacks to what you mention are concievable, but they require expertise and foreknowledge.

For instance if you were a business owner planning to frame someone for a murder committed on your property, you could take a unwatermarked video clip (since you own the cameras), edit it, and then replay it thru an encoder to create what would look like an umodified clip, with its authenticity attested to by its source watermark.