I've already seen a poster on FR say polygraphs don't work on people from some cultures because lies don't cause them any stress. It was clear he meant Arabs/Muslims.
Passing a polygraph wouldn't change the minds of 10 people.
First of all the do not 'detect' lies.
Secondly, they depend in large degree on the person giving them... their experience and professionalism.
Thirdly, it isn't black or white. Lieing or telling the truth. If the test comes up anywhere in the middle it can be thrown out.
But I guarantee you that if you pass a polygraph with flying colors, no remote hint of lying, you are 99.99% telling the truth.
The Mossad and the CIA are not idiots. There are some brilliant people working there who believe in this stuff. People here who make a joke out of the polygraph usually don't have a clue what they are taking about, never took one, never researched one (or their research consists of links to various web sights. ie. 'How to Sting the Polygraph' and other crap on the internet) or seen a PROFESSIONAL give one.