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Abstract

INGRAM, E. M. Test of a mock theft scenario for use in the psychophysiological detection of deception: I. May 1996, Report No. DoDPI96-R-0003. Department of Defense Polygraph Institute, Ft. McClellan, AL 36205.

The Zone Comparison Test (ZCT), a psychophysiological detection of deception (PDD) test, was administered to 20 healthy male and female soldier trainees programmed to be either deceptive or non-deceptive using the mock theft of a valuable coin. This pilot study was designed to determine the effectiveness of the coin theft as a mock crime scenario for laboratory tests with the ZCT. The scenario instructions and pretest were videotaped and presented to the subjects. The test questions were presented to the subjects using digitized voice. PDD tests were blind-evaluated by two independent scorers using the 3 position, ZCT scoring method. The frequencies of accurate determinations made were compared using proportionality tests. The independent scorers rendered a decision in 62% of the cases, and were unable to reach a decision (inconclusive calls) in 38% of the cases. When inconclusives were excluded, the average accuracy was found to be 84%, and was significantly better than chance (p <.05). However, neither independent scorer achieved an overall accuracy rate better than a chance level. Additionally, interrater agreement was found to be non-significant using the kappa statistic for multiple raters (p> .05). Despite the high accuracy rate found when inconclusives were excluded, the relatively high inconclusive rate, and low interrater agreement suggest that this procedure is not an effective laboratory mock crime procedure.

Key Words: psychophysiological detection of deception, mock crime scenarios, Zone Comparison Test

Director's Foreword

A perpetual problem with the psychophysiological detection of deception (PDD) discipline has been the shortage of supporting scientific research. Unfortunately, the research that does exist has frequently produced inconsistent or equivocal results. It is difficult, when evaluating such research, to determine why seemingly similar studies produced disparate results. One factor that may contribute to the disparate results among studies is the way subjects are manipulated.

In a typical laboratory study subjects participate in a procedure, usually called a mock crime, and then attempt to deceive the PDD examiner concerning their participation. The mock crime procedures used vary among reports, as do the reported accuracy rates of the subsequent PDD examinations. The results described in the reports are, at least to some extent, dependent on the efficacy of the mock crime procedure used. Use of the same mock crime procedure in multiple studies would greatly reduce the possibility that differences among study results were due to the use of different mock crime procedures. Such a "standard" procedure should be developed to have both validity and reliability. This report describes the first of a series of studies designed to develop and evaluate a "standard" mock crime procedure for use in multiple laboratory investigations. It is emphasized that this procedure is for use in the laboratory. It is, consequently, more important that the procedure produces valid reliable decisions than it is that the procedure emulates real life situations.

Michael H. Capps

Director