Many people wonder if a deceptive person can beat the polygraph test. This is very unlikely when the examination is administered by a qualified examiner, who can easily detect if the subject is trying to cheat the test with abnormal “countermeasure” behaviour. The polygraph instrumentation is basically recording medical changes in a person’s autonomic reactivity when they are asked questions, and any attempt to attempt deception to a question will be evident in the readings.
The test can take one and a half to two hours to complete. It consists of a pre-interview, (the longest part of the procedure), the actual test, and analysis of the test data.
Nervousness is not a problem during the test, as it is expected that a subject will be nervous, and this is taken into account.