With the pervasiveness of computer editing software, investigators and courts are learning to deal with digital fraud. Since pictures and documents stand as the bedrock of evidence, Farid has applied his studies to help judges and juries determine what's real and what's been altered. Recently he testified in an intellectual property lawsuit. The plaintiff accused the defendant of stealing software and offered a computer screen shot of their programming as proof. After running tests on the evidence, Farid determined the screen shot was faked.
"They tried to fool the court," he says. "I think the case has now turned from a civil suit to a criminal case going the other way."
But after working on two dozen cases, Farid has found there are far more accusations of fraud than there are actual instances of foul play. In another case, a man insisted that someone had digitally added his signature to a scanned document. If the charges were true, then a computer could probably detect tiny discrepancies between the signature and the rest of the image. Farid could not detect any and concluded that the man had in fact signed the document.
How Al Qaeda alters its videos
Spotting inconsistencies in pictures is a major aspect for computer forensics.
"One helpful aspect of digital files is that they leave records, whether you know it or not," says Nasir Memon, a computer science professor at Polytechnic University in New York City. "Whatever you do to an image, it will leave tell-tale signs – artifacts hidden in pictures."