Polygraph machine test results first used as admissible evidence in court

It takes a special breed of person to lie with a clear conscience. Most of us, brought up with a strong injunction against lying, are conscious that when we do lie, we violate an implicit trust. More than just feeling it, we react physiologically: pupils dilate, heart rate may increase, sweat might break out. Those are the types of reactions that the polygraph – lie detection – machines were designed to measure. Created by a medical researcher and a policeman in Berkeley, California, it was refined by another Berkeley alum, Leonarde Keeler, who first applied it to crime-solving.

On this day, February 2nd, 1935, the results of Keeler’s polygraph test were used in a criminal trial, marking the first time the invention was used as admissible evidence. Two men in Wisconsin failed to pass the polygraph, leading to their eventual conviction.

Despite its sound principle, the polygraph’s accuracy is in wide dispute. As it measures physiological responses, any person who can suppress those responses would easily pass. That was the case with famed Soviet spy Aldrich Ames: he passed two polygraph tests while also passing secrets along to the Russians. When he was finally caught and asked how he managed to pass the polygraph tests, he said he just followed his minders’ advice to  “Get a good night’s sleep, and rest, and go into the test rested and relaxed. Be nice to the polygraph examiner, develop a rapport, and be cooperative and try to maintain your calm.”