"Lie Detectors" are a crock.

http://www.zoklet.net/totse/en/politics/police/162007.html

"Police misuse of nervousness detectors has a sorry and disturbing history. Prior to the advent of DNA analysis (which we shall discuss later), police either believed or scoffed at a rape victim's allegations based upon how she performed on their nervousness detector. The traumatized victim was typically wired up to the machine and asked questions such as this: "Did the alleged assailant place his hand on your breast?" "Did the alleged assailant violently tear your skirt and remove your panties?" "Did the alleged assailant have an erection?" "Did the alleged assailant forcefully insert his penis into your vagina?" "Did the alleged assailant threaten to slit your throat if you refused to cooperate?"

It is truly stating the obvious that these questions would evoke an intense emotional reaction in any woman who had recently suffered the horrors of molestation, because such questions would remind her all-too-vividly of the crime perpetrated against her. It is likewise fair to say that even a woman who had not been raped would be emotionally traumatized by such probing and intimate questions leveled at her by a stranger, who was almost invariably a man.

But police didn't see things that way. If the rape victim became emotionally agitated during the inquisition -- as revealed by the nervousness-detecting machine -- then she was probably lying. She was inventing the rape story to attract sympathetic attention to herself, or to frame someone she disliked, such as an ex-boyfriend. When answering police questions, she displayed signs of anxiety "because her conscience was bothering her." And her conscience was bothering her "because she was lying.""

And:

"Meanwhile, back at the CIA, Ames had submitted year after year to all routine nervousness-detecting tests required of CIA employees. Each time, Ames passed the test without arousing suspicion that he was a traitor. Even a cursory examination of Ames's finances or possessions would have instantly revealed that his meager government salary could not support his opulent living. But why should the government conduct a real-world investigation when it's so much easier to use a nervousness detector instead? After being tipped off, the FBI finally arrested Ames in 1994, ten years after he had first masked his crimes using bogus "lie-detector" results. Said Ames from behind prison bars, "You have to realize that the government swears by these lie detectors. First, they swear that they don't swear by them; then they swear by them. I always found that if I got a good night's sleep before the test and just relaxed, I could pass without any problem.""