There are many legitimate and useful techniques used by police investigators; these include forensic analyses conducted in a police laboratory, document examination to identify signatures, and photography. The polygraph is used specifically in the interrogation of criminal suspects. The polygraph test is based entirely on changes in blood pressure and respiration which accompany emotions such as tension and anxiety which a guilty suspect will feel when he is forced to answer questions regarding his activities and their relationship to the crime. The examination consists of routine questions unrelated to the crime, from which the examiner can obtain a baseline reading. When a person lies during the examination, the instrument reveals violent fluctuations in blood pressure. This article contains the transcript of an impromptu polygraph demonstration conducted by the author.