Polygraph

[Bree Fletcher]

Its not all about faking, either. Here's another example. A teenaged boy is suspected of killing a local girl, and he takes the lie detector test. This is the first time he has been brought to the police, and every waking moment, he is scared like crap. While he takes it, he breakes down, and the lie detector says that he is lying, while he really was telling the truth. In this case, the innocent boy goes to Jail, the real criminal is on the loose, and police will find that the boy didn't do it after twenty years of jail life, and a load of regret.

Here, Professor X. Even if faking it doesn't actually work, (which I'm sure someone trained to can do even under stressful circumstances,) this is a good reason not to take polygraph tests at face value.