Truth and Consequences
Scientists are scanning the brain for traces of guilty knowledge
On July 22, 1977, the body of retired police Captain John Schweer lay bleeding on a railroad track in Council Bluffs, Iowa. Blame for the murder fell on teenager Terry Harrington, who has spent over two decades in a state penitentiary protesting his innocence. Now Harrington says he finally has proof that exonerates him. A new technology called "brain fingerprinting" suggests that Harrington's brain doesn't contain memories of the crime scene, but it does recognize specific details about the concert he says he attended on that fateful night.
Reading someone's memories through a helmet of electrodes sounds like science fiction. But surprisingly, scientists say they can do just that. The Harrington case is the first time lawyers have ever submitted such brain measurements to a U.S. court, and within days a judge will either reject them as "junk science" or accept them as evidence that could help reopen Harrington's case.
Until now, detectives have only had polygraph machines, or "lie detectors," to search for physiological measures of guilt and lies. But critics say polygraphs are hopelessly flawed because they measure emotional responses like blood pressure, breathing, and sweating. Nervous truth-tellers can appear guilty while cool liars look innocent, and people can beat the machine. Although polygraph tests have been the mainstay of lie detection since the 1920s, they're controversial enough that most states don't allow them as evidence. This month, the National Academy of Sciences will start a major review of polygraph tests' scientific validity at the request of the Department of Energy, which uses them to screen employees.
Many researchers hope they can do better than polygraphs by targeting the source of the lie: the brain. The "brain fingerprinting" technique used on Harrington was developed by Lawrence Farwell, a scientist and businessman at Brain Wave Science in Fairfield, Iowa. Farwell's technique exploits a signal that the brain emits when it perceives something familiar.
If a person watches random numbers flash on a screen, for example, the brain will suddenly show a distinctive electrical response called the P300 if personal information like a home phone number pops up. Scientists have known about the P300 response for decades, but no one has tried to apply it in a real-world criminal situation. Farwell believes it is valid in the Harrington case because he found details about the crime and Harrington's alibi that weren't in court transcripts or newspapers. For example, the murderer escaped by running behind a building through waist-high weeds and grass. According to Farwell, the real murderer would remember tearing through this thick underbrush. But when Farwell showed Harrington a photo of the building, the convict said he didn't know what lay behind it. And when presented with words such as "cement and blacktop," "sand and gravel," and "weeds and grass," Harrington had no special brain response to the correct answer.
Lacking knowledge. The test isn't a lie detector and doesn't prove Harrington's innocence, Farwell says. But Harrington "does not have certain critical details about the crime stored in his brain. A judge or jury must decide how they're going to interpret that."
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