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Abstract

BRADLEY, M. T., CULLEN, M. C. and CARLE, S. B. Control question tests by police and laboratory polygraph operators on a mock crime and real events. December 1993, Report No. DoDPI93-R-0012. Department of Defense Polygraph Institute, Ft. McClellan, AL 36205.

Males and females, truthful or deceptive, about a real life embarrassing story or a laboratory mock crime were examined with Control Question detection of deception tests. Exams were conducted either by a police or a laboratory trained polygraph operator. Subjects were more reactive to event relevant questions when deceptive than when truthful. Police scored subject records more towards innocence, whereas, laboratory investigators scored them more towards quilt. This was especially pronounced with SRP measurement on embarrassing stories. Such a result could mean that laboratory investigators when mistaken would have a tendency to classify innocent people as guilty when dealing with real events, whereas, the police when wrong would tend to classify the guilty as innocent.

Key-words: Control Question Test (CQT), police examiners, lab examiners, polygraph tests, psychophysiological detection of deception

Director's Foreword

This study represents an unique undertaking in attempting to resolve the problem of assessing criterion validity of the Control Question Technique (CQT) in the laboratory, in a manner which provides for higher confidence when generalizing the results to field examinations. Arguments have been raised by scientists and PDD examiners alike as to the generalizability of laboratory research results to real life PDD examinations. A significant difference exists on which these views are based. Scientists have reported that the accuracy rates found in the laboratory setting could decline as paradigms become more like real situations. PDD examiners believe that the lack of any threatening situation in the laboratory may cause lower arousal levels than experienced in field examinations.

In this study, a laboratory mock crime and real life embarrassing events were the relevant issues addressed during CQT psychophysiological detection of deception examinations. The tests were administered by laboratory examiners highly trained in psychology, psychophysiological measurement, and general testing; and, police polygraph examiners specially trained for criminal polygraph work and having general criminal interrogation experience. Electrodermal and respiratory associated data were collected by laboratory examiners while police examiners had an additional cardiovascular channel.

The high accuracy at which both examiner groups discriminated between the truthful and deceptive examinees demonstrates the robust state of the CQT. Especially interesting were the findings of an examiner's effect which suggests that as laboratory testers move away from their familiar mock crime paradigm, they make more false positive errors; whereas the police examiners remain consistent across different situations. The authors suggest that as a result of their experience with emotional or highly stressed suspects, the police examiners may be able to more effectively create or present the CQT. These findings support the argument that there may be some degree of difficulty in generalizing laboratory PDD examinations to the field, especially when the examinations are not conducted by trained PDD examiners.

Michael H. Capps

Director