Practical methods for detecting mendacity: a case study.
This study demonstrates the concurrence of the use of objective verbal and nonverbal signs and lying. President Clinton's Grand jury Testimony of August 17, 1998, was examined for the presence of 23 clinically practical signs of dissimulation selected from 64 peer-reviewed articles and 20 books on mendacity. A segment of his testimony that was subsequently found to be false was compared with a control period during the same testimony (internal control). A fund-raising speech to a sympathetic crowd served as a second control (external control). The frequencies of the 23 signs in the mendacious speech were compared with their frequencies during the control periods, and the differences were analyzed for statistical significance. No clinical examination was performed nor diagnosis assigned. During the mendacious speech, the subject markedly increased the frequency of 20 out of 23 signs compared with their frequency during the fund-raising control speech (p < .0005). He increased the frequency of 19 signs compared with their frequency during the control period of the same testimony (p < .003). The 23 signs may be useful as indicators of the veracity of videotaped and scripted testimony. If these findings are confirmed through further testing, they could, with practice, be used by psychiatrists conducting interviews.