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The Ultimate Lie Detector?

Publication Date: 
December 01, 2009
California Lawyer
Tom McNichol

Professor Hank Greely offered his perspective on the current state of fMRI technology in the context of lie detection:

Telling a lie—it's one of the easiest things for a human being to do. It's also one of the hardest in the world to detect.

But that hasn't stopped people from trying. When the ancient Chinese questioned suspects about an alleged crime, they used to make them chew grains of rice. After interrogation, if the rice in the suspect's mouth was dry, it was assumed that tension created by deception had blocked the flow of saliva. Guilt by rice.

Now, new brain-imaging technologies promise to revolutionize the ancient art of lie detection to go far beyond what polygraphs can do, and in the process turn what once was little more than superstition into a verifiable science. (See the sidebar "The Truth About Polygraphs.")


"I don't think fMRI technology is close to being ready for prime time," says Hank Greely, a bioethicist at Stanford Law School. "I don't think there's proof that it should be used now. I wouldn't go so far as to say that no one should offer it, though it would be nice to have a regulatory scheme that treated it the way the FDA treats new drugs or medical devices. But I certainly wouldn't pay for it or put any confidence in the results at this point."


"It'll be interesting to see how this plays out," says Stanford's Greely. "I think the technology could be proven to be sufficiently reliable within the next 5 to 20 years. But I'd really hate to have it pushed prematurely, because some people's lives could really be harmed as a result."