Slate senior writer William Saletan comments on polygraphy. Excerpt:
Two weeks ago, besieged by speculation that he had killed former Washington intern Chandra Levy, Rep. Gary Condit, D-Calif., launched a strategic retreat. He granted the police a long interview, reportedly admitting to an affair with Levy. The cops emerged to say he had answered all their questions. Condit gave them a DNA sample and let them search his apartment. Then his lawyer, Abbe Lowell, delivered the coup de grâce: He announced that Condit had passed a private polygraph exam. The cops, the Levy family, and many commentators cried foul, but the speculative bubble around the congressman had burst. The old headlines about his role in Levy’s disappearance faded, replaced by talk of serial killers, Web sites, and fresh searches for her body.
Step back for a minute and think about this: A man has attached himself to a machine, uttered the word “no” three times, and derailed an investigation that had become a national frenzy. No information or explanation was necessary. The search for truth used to be understood as a verbal process of questions, answers, and probing contradictions between statements and evidence. But the ascent of technology has nurtured confidence in a more mathematical approach. We think the polygraph can reveal the truth. And it can–but only as part of an enterprise older, larger, and subtler than itself. The verbal and social elements of investigation are just as influential inside the polygraph room as they are outside it. By focusing our attention and faith on the machine, we allow its users–police and suspects alike–to manipulate those elements to their advantage.