In various sources one can read that the validity of the test is 97%, and even higher. On the contrary, recited in the instrument is not entirely accurate. This false information is confirmed as experts, who are checking and stakeholders. Primarily this is done in order to increase the demand for the use of this type of service. Moreover, such service is not cheap, which means he brings a good income. Also when performing this test before it began, the subject is the psychological impact. Therefore, the specialist would win even before the test.
The polygraph can easily fool the normal social psychopath. This is because it cannot adequately perceive and evaluate the situation, and he is no such thing as morality. Liars also are easy to trick this device is recited. Often they sincerely believe in what they say, so the polygraph perceives their speech as the truth. Easily cope with this task and talented actors. Still easy to cheat the polygraph and covert ops employees that have appropriate training.
In order to successfully pass a polygraph, you need to get rid of the guilt and to overcome your fear. You need to be sure, even if the past is any sins.