Lie Detectors Are Junk Science, but We Keep Using Them
You’ve probably seen a lie detector in a movie or TV show, its stylus scratching an ink line across a scrolling page and jumping when the subject lies. Sometimes the polygraph is presented as infallible; sometimes its scrutiny can be evaded. In a spy thriller, the hero might put a pin in his shoe: Stepping down on a sharp point, the theory goes, will cause sufficient stress to spike his blood pressure, disguising false statements. In other tales, talented operatives can simply meditate their way down to a state of calmness and therefore appear not to be lying.
Even in the early days of the lie detector, the device’s advocates seemed dimly aware that simply being questioned by the police might make a suspect flustered or nervous and, thus, perhaps give the impression of being untruthful. Whose blood pressure wouldn’t spike when faced with criminal charges? Sure enough, police quickly found that people who were given polygraphs tended to panic. They also tended to confess: to all sorts of offenses, from card games to illegal alcohol, separate from the crimes under investigation.
Amit Katwala, a reporter at Wired, tackles the lie detector’s early history in Tremors in the Blood. He focuses on its origins in Berkeley, California, in the 1920s and on some cases that both brought it to prominence and raised questions about its validity..
The machine attracted controversy right from the start. Katwala covers the case of Henry Wilkens, who was (probably) guilty of killing his wife but managed to get away with it. This was a front-page news story in San Francisco in 1923, and it was an opportunity for the lie detector to prove its value. Unfortunately for the prosecution, when he was subjected to a test in front of a crowd of onlookers, Wilkens passed. In the eyes of the polygraph boosters, the device had failed—or was failed, in being applied incorrectly. Wilkens was acquitted and the San Francisco Police Department swore off lie detectors.
The Wilkens case shows more about why police forces (and the public) wanted the lie detector, or something like it. A young woman had been shot to death. It was the sort of violent crime that was on the rise in the early 1920s, panicking suburbanites and leading authorities t
Article from Reason.com