Lie detector test. Pulse meters on a man's fingers during a lie detector, or polygraph, test. A polygraph records changes in a number of physiological processes, as a series of questions are asked by an examiner. As well as measuring heart rate with these pulse meters, blood pressure and respiration rate are also measured. The examiner interprets the results to determine if the subject demonstrated deceptive behaviour. The reliability of polygraphs is controversial and their evidence is not admissible in court.