This is misunderstood. The Polygraph is not scientific, and can't reliably detect dishonesty. However, lots of people will admit to things under interrogation and bullying. What the polygraph is actually doing for the interrogators is simply to provide a formal way to read body language. And of course, to provide what is effectively a robot-bad cop. "Gee, I dunno, the test says you're lying. Are you sure there's not anything you want to tell me?"