Can Digital Photos Be Trusted?

"Everyone is buying low-cost, high-quality digital cameras, everyone has a Web site, everyone has e-mail, Photoshop is easier to use; 2004 was the first year sales of digital cameras outpaced traditional film cameras," says Hany Farid, a Dartmouth College computer scientist and a leading researcher in the nascent realm of digital forensics. "Consequently, there are more and more cases of high-profile digital tampering. Seeing is no longer believing. Actually, what you see is largely irrelevant."

That´s a problem when you consider that driver´s licenses, security cameras, employee IDs and other digital images are a linchpin of communication and a foundation of proof. The fact that they can be easily altered is a big deal-but even more troubling, perhaps, is the fact that few people are aware of the problem and fewer still are addressing it.

It won´t be long-if it hasn´t happened already-before every image becomes potentially suspect. False images have the potential to linger in the public´s consciousness, even if they are ultimately discredited. And just as disturbingly, as fakes proliferate, real evidence, such as the photos of abuse at Abu Ghraib prison in Iraq, could be discounted as unreliable.

And then there´s the judicial system, in which altered photos could harm the innocent, free the guilty, or simply cause havoc. People arrested for possession of child pornography now sometimes claim that the images are not of real children but of computer-generated ones-and thus that no kids were harmed in the making of the pornography (reality check: authorities say CG child porn does not exist). In a recent civil case in Pennsylvania, plaintiff Mike Soncini tussled with his insurance company over a wrecked vehicle, claiming that the company had altered digital photos to imply that the car was damaged before the accident so as to avoid paying the full amount due. In Connecticut, a convicted murderer appealed to the state supreme court that computer-enhanced images of bite marks on the victim that were used to match his teeth were inadmissible (his appeal was rejected). And in a Massachusetts case, a police officer has been accused of stealing drugs and money from his department´s evidence room and stashing them at home. His wife, who has accused him of spousal abuse, photographed the evidence and then confronted the cop, who allegedly destroyed the stolen goods. Now the only evidence that exists are digital pictures shot by someone who might have a motive for revenge. "This is an issue that´s waiting to explode," says Richard Sherwin, a professor at New York Law School, "and it hasn´t gotten the visibility in the legal community that it deserves."

So far, only a handful of researchers have devoted themselves to the science of digital forensics. Nevertheless, effective, if not foolproof, techniques to spot hoaxes are emerging-and advances are on the horizon. Scientists are developing software, secure cameras and embedded watermarks to thwart image manipulation and sniff out tampering. Adobe and Microsoft are among the private funders, but much of the work is seeded by law-enforcement agencies and the military, which face situations in which more than just reputations are at risk. (Maintaining the integrity of the chain of evidence is of utmost importance to law enforcement, and the military is concerned about the veracity of images arriving from, say, Iraq or Afghanistan. Does that picture really portray Osama bin Laden? Are those hostages in the grainy video really American soldiers?)