A typical polygraph starts with a pre-test interview designed to establish a connection (or find a control) between the tester and the testee and to gain some preliminary information which will later be used for "Control Questions ".

While some people believe that polygraph tests are reliable, there is little scientific evidence to buttress this claim. For example, while some claim the test to be accurate in 70% - 90% of the cases, critics charge that rather than a "test", the method amounts to an inherently unstandardizable interrogation technique whose accuracy cannot be established. It is interesting to note that, so far, no scientific study has been published that offer convincing evidence of the validity of the polygraph test.