Lie detector traces. Traces from an analogue lie detector, or polygraph, machine. The machine records changes in a number of physiological processes, as the examiner asks a subject a series of questions. The processes measured include blood pressure, respiration rate and heart rate. The results are shown as traces drawn on moving paper. 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.