Let’s get one thing clear up top. Polygraph tests cannot tell when a person is lying. Cop shows may insist otherwise, but in reality they’re pure junk science, and there’s a good reason they’re inadmissible in court.
However, they are useful as a tool for psychological intimidation. The simple act of hooking someone up to a machine they’ll have seen a thousand times in movies and TV shows puts pressure on you. As thinking goes, if you’ve been fooled into believing that the polygraph can detect lies, you’ll be more inclined to tell the truth.
