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Awareness of crime-relevant information and the Guilty Knowledge Test

Article Abstract:

The effects of awareness of crime-relevant information on the detection of deception with the Guilty Knowledge Test were examined. Student subjects were assigned to 1 of 3 groups: a guilty group, members of which committed a mock crime; an innocent group aware of details about the crime; or an innocent group unaware of such information. After following instructions, subjects were tested on the polygraph with a 10-item Guilty Knowledge Test and were offered $20.00 for an innocent test outcome. Skin resistance response scores of guilty subjects lying about crime-relevant information were higher than those of innocent uninformed subjects, whose scores in turn were higher than those of innocent unaware subjects. This replicated findings of an earlier study in which similar procedures were used and supported the view that subjects aware of crime-relevant information can appear less deceptive than subjects lying about crime-relevant information. (Reprinted by permission of the publisher.)

Truthfulness and falsehood

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Detection measures in real-life criminal guilty knowledge tests

Article Abstract:

The present study provides a first attempt to compare the validity of the respiration line length (RLL) and skin resistance response (SRR) amplitude in real-life criminal guilty knowledge tests (GKTs). GKT records of 40 innocent and 40 guilty Ss, for whom actual truth was established by confession, were assessed for their accuracy. When a predefined decision rule was used and inconclusive decisions were excluded, 97.4% of the innocent Ss and 53.3% of the guilty Ss were correctly classified with the SRR measure. For the RLL measure, the respective results results were 97.2% and 53.1%. The combination of both measures improved detection of guilty Ss to 75.8% and decreased detection of innocent Ss to 94.1%. The combined measure seems to be a more uselful means of identifying guilty suspects than each physiological measure alone. The results elaborate and extend those obtained in a previous field study conducted by Elaad (1990). (Reprinted by permission of the publisher.)

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Deception and nondeception in Guilty Knowledge and Guilty Actions polygraph tests

Article Abstract:

Two polygraph tests, the Guilty Knowledge Test (GKT) and the Guilty Actions Test (GAT), were compared in a laboratory setting. Men (N=120) who committed or witnessed a mock crime were required to answer "no," to repeat items, or to remain silent in response to items on the GKT or the GAT. A monetary reward was promised for appearing innocent on the test. An interaction with scores based on skin resistance responses showed that innocent witnesses tested on the GKT and guilty participants tested with either the GKT or the GAT scored more in the guilt direction than did innocent witnesses tested on the GAT. Furthermore, participants who were required to say "no" were more reactive to key items than were participants in the silent group. (Reprinted by permission of the publisher.)

Analysis

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