I think polygraphs have their place in criminal investigations, as just another interrogation tool to see how people behave when they are questioned. The fact that so many things can affect the results, whether deliberate or not, is why they can’t be depended on in the same way as, say, DNA tests can be. But sometimes, simply the fact that some people refuse to take a polygraph test, or some people fail them so dramatically, can guide the investigators toward a new person to follow up on.