Instrument-based truth tests have been used by law enforcement, the military, and the private sector since the first “lie detector” was invented in the 1920s. In 1908, Hugo Munsterberg wrote “On the Witness Stand,” in which he suggested instrumentation be attached to witnesses as they give testimony in order to monitor respiration changes, cardiovascular changes, muscle tension, skin temperature, etc., so as to ensure the truthfulness of witnesses’ testimony. In 1914, Vittorio Benussi, an Italian philosopher and psychologist, published research that indicated breathing changes could give accurate determinations of deception. Additional research by William Marston published in 1917 indicated that systolic blood pressure changes could also accurately detect deception. Such research led to the development of the polygraph in 1921 by John Larson. In the mid-1930s, Leonarde Keeler added an additional physiological parameter to the polygraph, which monitored electrodermal (sweating) activity. Today’s polygraph still monitors the three basic physiological functions of blood volume/pressure, respiration, and sweating, but the instrumentation has evolved. Pneumatic sensors have been replaced with electronic versions, and electronic sensors have been replaced by computerized measurement devices. In the 1960s, U.S. military research led to the marketing of the first instrument designed to measure voice changes believed to be directly associated with psychological stress and possible deception. Other voice stress devices have evolved from other manufacturers. More recent truth-detection research involves thermal imaging, pupilometry, and brain waves. Still, the polygraph remains the standard truth test for most law enforcement and government agencies. This article discusses how to find a qualified polygraph examiner and the importance of law enforcement agencies’ developing a published policy on the use of any deception detection equipment. 17 notes