How accurate is a lie detector test?

Industry research suggest polygraph accuracy to be between 90 and 98 percent especially when incorporating best practice with validated testing question formats and computerized polygraph technology.

Accuracy of polygraph examinations Results from several decades of scientific study have consistently supported the validity of the hypothesis that the combination of instrumental recording and statistical modeling can discriminate deception and truth-telling at rates significantly greater than chance. Scientific reviews of peer reviewed polygraph studies have borne this out repeatedly. Abrams (1989) surveyed the published literature and reported an accuracy level of .89. Honts and Peterson (1997), Raskin (2002), and Raskin & Podlesny (1979) reported the accuracy of polygraph studies as exceeding .90. The systematic review completed by the Office of Technology Assessment (1983) suggested that laboratory studies had an average unweighted accuracy of .83, with slightly higher accuracy, .85 from field studies at the time. Crewson (2001) reported an accuracy rate of .88 for diagnostic polygraphs in a comparison with medical and psychological tests. The National Research Council (2003) concluded with reservation that the polygraph differentiated deception from truth-telling at rates that were significantly greater than chance though less than perfect, and reported a median ROC of .89 for field studies and .86 for laboratory studies. Lie detector, also called a polygraph

instrument is used for recording physiological phenomena such as blood volume, pulse rate, galvanic skin response and respiration of a human subject as he/she answers a series of questions put to them by a trained operator; Physiological phenomena usually chosen for recordings are those not greatly subject to voluntary control. This data is then used as the basis for making a judgment as to whether or not the subject is lying. With the addition of specialised computerised software Polygraph results are extremely reliable. Polygraph instruments have been used in police interrogation and investigation since 1924 in various forms, and are widely used to this day as a investigation tool for the FBI the CIA and most the Federal Government agencies in the USA and 69 countries around the world.

The latest research on lie detector test accuracy for specific issue testing formats has an average accuracy rate of 98% the following format hits accuracy rates at 98 % with inconclusive s excluded.

Scientific references Mangan, D. J., Armitage, T. E., Adams, G.C. (2008a). A field study on the validity of the QuadriTrack Zone Comparison Technique. Physiology & Behavior, 95, 17-23.
Mangan, D. J., Armitage, T. E., Adams, G. C. (2008b). Rebuttal to objections by Iiacono and
Verschuere et al. Physiology & Behavior, 95, 29-31.

A Comparison of Fingerprint Analysis, Eyewitness Testimony, Handwriting Analysis and Polygraph Test results

In an article published in the Journal of Forensic Science 23 (3), 596-601, published in 1978 by Jan Widacki and Frank Horvath, entitled
“An experimental investigation of the relative validity and utility of the polygraph technique and three other common methods of criminal identification.”,
Researchers compared the polygraph, handwriting analysis, eye witness testimony and fingerprints in a mock crime scenario.

80 subjects (college students) were divided into 20 groups of 4. In each sub-group there was one guilty participant and three innocent ones.

The task of the guilty participant was to go to a particular building; present themselves to a person whom they did not know before hand; give an envelope to the specified person; receive a package using a fictitious name; sign a receipt for the package using the fictitious signature and then steal the contents of the package.

All participants were then subjected to a polygraph.

The document receipts and envelopes were subjected to handwriting analysis compared against handwriting standards supplied by all participants.

Fingerprints collected from the envelope and receipts were compared to record prints of all participants.

The eye witnesses to the crimes were provided full front photographs from which to select the perpetrator who signed for and stole the packages.

All forensic technicians were blind to the identity of the perpetrators as was the eye witness but all technicians were aware that one in each group of four was the perpetrator and three were innocent as were the eyewitnesses.

The following results were recorded with inconclusive results removed for all:

Polygraph -18 correct identifications, 1 error and 1 inconclusive result for an over all accuracy of 95%.

Handwriting – 17 correct identifications, 1 error and 2 inconclusive results for an overall accuracy of 94%.

Eyewitness – 7 correct identifications, 4 errors and 9 inconclusive results for an over all accuracy of 64%.

Fingerprints – 4 correct identifications, 0 errors and 16 inconclusive results for an overall accuracy of 100%.

Based on the above findings the Polygraph is as good if not better than most commonly used identification techniques .