Lie detectors aren't remotely reliable enough to be used like this. Sufficiently skilled people can beat them and people tend to react to the sensitive questio

Lie detectors aren't remotely reliable enough to be used like this. Sufficiently skilled people can beat them and people tend to react to the sensitive questions (is the machine going to falsely say I'm lying???) even when telling the truth. However, I do believe they have a role in law enforcement. The same hardware can be repurposed for a guilty knowledge test. The police keep secret the details of the crime. If they catch a suspect they hook them up to a lie detector and make them repeat the details--some true, some false and compare the reactions. (I do not consider this compelled testimony as they're just reading a script.) Someone who shows a sufficient pattern of hitting on the true ones knows the details. It won't false positive because the innocent doesn't know which answers are the guilty ones (to be safe the person doing it should likewise not know so you don't get a Clever Hans effect) and won't tense up because if it. It could statistically but if you have enough questions you can make this possibility vanishingly small. There still is a chance of a false negative if the guy can beat it (unlikely) or actually didn't note the details you're asking about.