USA Today technology writer Andrew Kantor comments on polygraphs in his weekly CyberTalk column. Excerpt:
I learn a lot watching television. That is, I learn a lot by watching television and thinking, “That can’t be right!” then doing the research to find the full story.
Television butchers technology. It has to. There’s no time in your average crime drama, say, to go into the details of tracking a cell phone or running someone’s DNA; what takes seconds on TV often takes hours in the real world. (I understand that they’ve only got 42 minutes to work with, so I don’t sweat the time thing.) It’s when they deviate from reality so much that my goat gets got.
For example, I gather I’m one of the few Americans who doesn’t watch 24. I stopped after the first episode of the first season, when Jack Bauer (that’s Kiefer Sutherland to you and me) demanded of his geek-in-residence, “I need every Internet password associated with this phone number!” And he got it. It just doesn’t work like that.
One thing occasionally comes up on TV that I wasn’t sure which category it belonged to–“accurate but glossed over” or “totally wrong.” That was polygraphs. Lie detectors. On TV, the suspect is hooked up to a machine that traces a dozen or so lines on scrolling graph paper. When she tells the truth, the lines barely move. When she lies, the lines vibrate like a seismograph in an 8.0 earthquake.
My guess was that in the real world a lie isn’t quite so obvious, but that a trained examiner would be able to spot it right away.
Boy was I wrong.
It turns out that polygraphy is not only an incredibly inexact science, but that reading the results of a lie detector is almost entirely subjective. In short, lie detectors don’t work. But people’s lives have been ruined by them.
The problem isn’t that the machines don’t record something–they do: heart rate, respiration, sweat-gland activity, and so on. But what the changes in those numbers mean is entirely up to interpretation.
Obviously there are two sides to this. On the one you have the American Polygraph Association (APA) and some law enforcement agencies. Neither of these are what you would call objective. The APA’s existence depends on people accepting that lie detectors work, and as we’ve seen all too often, police and district attorneys are happy to have something that appears to provide evidence that can convict someone. (Lie detector tests are rarely allowed as evidence against someone in court — that should tell you something — but “failing” a test can sway public opinion, and jury members aren’t hermits.)
On the other side you have, well, dozens of groups and organizations with names like AntiPolygraph.org and StopPolygraph.com. If you’re like me, you might at first blush think these are fringe groups with their own (hidden) agenda, and that they aren’t about to provide unbiased information. After all, there’s always a conspiracy theorist to be found.
Except that also on the anti-polygraph side I found the American Medical Association, the American Psychological Association, and 60 Minutes. They all found essentially the same thing: Lie detectors show what the examiners want them to show.