Do they work?
The credibility of the lie detecting was challenged almost as soon as it was invented, and there is much debate about its accuracy.
The fundamental premise that lie detecting tests measure deception, is incorrect.
Lie Detection methodologies measure responses to questions and compares the responses to control questions with responses to relevant questions. Theoretically liars will show increase arousal when answering the relevant questions, whereas truth tellers will not. Unfortunately, there is no sound theory to back this up.
There are several different reasons why a test may be inaccurate. These include the questions being poorly formulated and the interviewer misreading the results.
If the examiner is well-trained, if the test is properly carried out, and if there’s proper quality controls, the accuracy is estimated between 80%-90%. This being higher than the average person’s ability to tell if someone is lying.