ABSTRACT
Polygraph techniques can be categorized into recognition tests and truth tests, with the latter group divided into noncomparison question tests and comparison question tests.
The first documented technique, used by Cesare Lombroso in 1895, was a recognition test. A child had been molested and murdered. He showed a suspect a series of pictures of children while using an instrument to monitor changes in blood volume in the suspect’s hand. He theorized that if the suspect was innocent, none of the pictures would have any meaning to him since they were all pictures of children he did not know. However, if this was the guilty person, when he viewed and recognized the picture of the child he murdered, he would experience a psychophysiological change resulting in detectable blood volume changes in his hand.
