We learned to beat them in my psych class in college. Was kinda neat. Anyway, a trained professional can usually beat a polygraph anyway. Ever wondered why Middle eastern politicians always wear sunglasses? It's because the eyes usually give away when you're lying. Pupils have a tendency to dilate when you are lying and you have a tendency to glance up and left when lying, up and right when trying to recall information. Again, this is not infallable, and can be beaten, but hey.