Of course it doesn't actually detect lies, there's no way it could. What they do is use it as a tool against you to try to force a confession. It's absolutely

Of course it doesn't actually detect lies, there's no way it could. What they do is use it as a tool against you to try to force a confession. It's absolutely a bluff on the part of the interviewer, and they know it. What they'll do is sit you down after the "results" come in and say: "hey, we both know you weren't 100% truthful during the test, the results clearly indicate you lied during key parts of the interview. Is there anything you'd like to tell us?" I cannot stress enough that the actual results of what the polygraph say are not factored in whatsoever.