Climbing Inside The Criminal Mind: THE BRAIN SCIENTIST

He went to Harvard, works in Iowa and loves swing dancing. That's not the typical profile of an anticrime crusader, but Lawrence Farwell is an unusual guy. While developing technology that would allow the vocally paralyzed to speak, he stumbled across a trove of seemingly extraneous signals stored in the brain. He began looking for a way to put that information to use. Result: a new forensic technology he calls brain fingerprinting.

Here's how it works: Farwell fits a suspect with a sensor-filled headband. By flashing a series of pictures on a screen, he can read the subject's involuntary reactions to them. When there's something familiar about an image, it triggers an electrical response that begins between 300 and 800 milliseconds after the stimulus. Scientists have studied these "p300 bumps" for years. Farwell believes that, combined with other measures--he has patented which ones he looks at--he can determine if a subject is familiar with anything from a phone number to an al-Qaeda code word.

Indeed, the CIA has funded his research with more than $1 million, and a former FBI point man for biological and chemical weapons has joined Farwell's firm. Critics say that p300-type testing needs a lot of refinement before it's a perfect polygraph, but such criticism doesn't deter Farwell. "The fundamental task in law enforcement and espionage and counterespionage is to determine the truth," he says. "My philosophy is that there is a tremendous cost in failing to apply the technology."

--By Sarah Sturmon Dale