Some thoughts on analog video tampering

Despite all the hype over digital technologies, anyone who works in forensics and video surveillance knows very well that analog video is still alive. It’s dying, of course, but sometimes you will still have to digitize old VHS for two reasons:

  • The source is a surveillance VCR that is still working (it hasn’t been replaced yet)
  • The source is from an old case (I’ve been found myself working on cases spawning from the eighties to yesterday)

Of course, it does not happen often (at least to me) to work in VHS;  but it happens.  I’m usually happy since it sometimes leaves more room for processing than super compressed digital videos so widely used today.

However, in this post I will speak of a more specific thing related to analog: tampering.

In the last year I’ve been working on three forensic cases where there was the strong suspicion of working on video material that was not original. The interesting thing was that all of this cases the suspicion was confirmed to be true. The cases were very different: in one case I had some avi and audio files, in one case a MiniDV cassette (digital), and in another case a VHS tape.

In every single case we found proof that we were not working on original material but on something that has been (accidentally or on purpose) manipulated. Considering that with today’s technologies it is very easy and cheap to do some image and video manipulation – and two of the three videos were already digital – I still feel stroked that in all these three cases the manipulation has been done by analog techniques. And I don’t mean using professional grade hardware, but simply connecting two devices with an analog cable and controlling the playback and the recording devices by their control buttons.

The techniques used to discover this were very different and (maybe) the subject of some new post.  Some required writing specific software.  In others the tampering was apparent by simply looking at the videos.

What’s the lesson here? Never think: “They couldn’t have been doing that!”   They will do it: once, twice and even three times. There are things that an expert would see and dismiss as a method too stupid and obvious to fake evidence.  From what I have just seen, you should never exclude any possibility even if it sounds too ridiculous to be true.