Tuesday, February 2, 2010

Image Processing of Forensic Evidence

For those that missed it, here's a link to Dr. John C. Russ' seminar called Image Processing of Forensic Evidence that was part of NC State's Forensic Science Symposium. Thanks to Larry for putting this out there.

An excerpt from the seminar. Dr. John C. Russ: "... the image that has been given to me has been compressed with JPEG compression. Don't do that. If you are using a camera that does JPEG compression, sooner or later, there's going to be a cross examination that goes something like this. 'So officer, this picture was taken with a brand X camera that does JPEG compression, right?' 'Right.' 'And JPEG compression, according to the statement of the Joint Photographers Expert Group, is designed to preserve that information which is useful for people to identify familiar objects. Isn't that correct?' 'Well, yes.' 'So it's a lossy technique and it discards information that doesn't help in that situation. Can you show me what information has been discarded from this picture that might be exculpatory for my client?' And of course you can't, because what it throws away depends on the contents of the particular picture. The more detail that's there, the more it throws away. And, at that point, your credibility's been damaged and even if there is information in the picture, it's going to be hard to convince people ..."


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