Can you generally tell if any video tape or sound recording has been doctored or tampered?
If so, is it an easy/difficult process? Also, do you know (or have heard of) any ways of doctoring a tape without leaving a trace?

For the record, I'm asking in regards to a legal rule on evidence. Generally speaking, before a video tape/sound recording is admitted, you have to show a chain of custody (guardianship) to prove that no one could have tampered with the recording. I'm curious if providing expert testimony showing that a piece of evidence has not been tampered with would circumvent this rule.

2/11/2009 9:08:17 AM

Quote :

"Can you generally tell if any video tape or sound recording has been doctored or tampered?"

Unless it's truly obvious, no, not with the naked eye. You would have to take the tape and split the audio/video up and measure each part separately. You would also have to run filters on them to discern any spliced pieces of either.

Doctoring tapes well is hard. There is always a trace and human error, unless there is no original and you could add in the proper amount of noise and other variables. You just have to know what to look for.

Expert testimony wouldn't hold up unless there was evidence that the chain of custody hadn't been compromised.

2/11/2009 10:50:45 AM

This is a question that really needs to be forwarded to a lawyer who has knowledge of the relevant case law. The outcome of these kinds of questions are all based on previous rulings. In the case where there's a lack of precedent, you'd still need the opinion of a lawyer on the likelihood of the argument being upheld. If this is for a civil matter the opposing party would have to more or less prove that the tape was doctored for it not to be entered as evidence. I mean, look at all the sketchy shit the RIAA gets to pass off as evidence in their law suits. Criminal trials have much higher standards for evidence.

2/11/2009 11:50:00 AM

This isn't for a particular case or anything. I'm in law school at UNC and I just had a discussion with my Evidence Professor (Broun). I asked him about this concept in theory, and he said it would probably have a lot to do with how easily a doctored tape/audio recording can be exposed. If all doctored tapes leave some discoverable trace or marking, then a court may allow it if you could establish the beginnings of chain of custody (to show that the tape in question is the original, and the mechanism used to tape was working properly), as well as an expert testimony that the tape is unaltered....


although as he pointed out, without a proper chain of custody you wouldn't be able to prove that the tape offered for evidence was the original.

I suppose Seotaji is probably right.

[Edited on February 11, 2009 at 1:07 PM. Reason : ff]

2/11/2009 1:05:01 PM

If it's digital audio/video, then yes it is *possible* to prove authenticity, so far as its origin and cleanliness.

It does require that the media in question has been recorded on a closed system (no human interaction at-all, and no communication outside of its own subsystems). This presents a practical problem of how to get the information OFF the system for us to use it as evidence, as the system would then become immediately compromised. However, for legal proceedings, this would essentially start the chain of custody and human procedures could step in at this point to ensure the data remained pristine.

Within the system, a combination of self-encryption, steganography, environmental data collection and verification hashes would help ensure authenticity. This would also have to be contained on a platform and using a storage system of similar, circularly reliant, designs.

2/11/2009 3:45:08 PM