Japan is the only country where the polygraph with the concealed information test (CIT) is widely applied to criminal investigations. The CIT can reveal whether an examinee has knowledge of specific details of a crime. Furthermore, the CIT can extract crime-relevant information that investigative organizations have not yet uncovered. This article introduces how Japanese polygraphers take advantage of the CIT in criminal investigations. We also describe how polygraphs with the CIT are currently used in court. Then we propose statistical discrimination methods that can be easily applied to CIT interpretation in the field. Appropriate application of the statistical values is discussed. We hope that this article will facilitate more active use of the CIT outside Japan.
Currently, polygraph examinations in Japan use the concealed information test (CIT) to determine whether a suspect knows speciˆc details of a crime. The present study examined the accuracy of the CIT as a memory detection technique in a mocktheft experiment. Participants were randomly assigned to either an encoding or nonencoding group. An expert polygrapher who was not informed of the group assignments, conducted a CIT that consisted of two questions. One inquired about a card number chosen by the participant, and the other regarded an item that had been stolen. Analyses focused on the second question. Roughly 20 of cases were judged inconclusive while sensitivity and speciˆcity for the remaining cases were 86 and 95 , respectively. Analysis was repeated using modiˆed Lykken scoring, and rates of inconclusive cases, sensitivity, and speciˆcity by this method were 25, 83, and 91, respectively.
The concealed information test (CIT) can be used to assess whether an individual possesses crime-related information. However, its discrimination performance has room for improvement. We examined whether screening out participants who do not respond distinctively on a pretest improves the diagnosticity of a mock-crime CIT. Before conducting that CIT, we gave a pretest to 152 participants, 80 of whom were assigned as guilty. Pretest screening significantly improved the diagnostic value of the mock-crime CIT; however, it also led to a substantial number of undiagnosed participants (33.6%).Pretest screening holds promise, but its application would benefit from dedicated measures for screening out participants.
The concealed information test (CIT) estimates whether an examinee knows crime-relevant information on the basis of diŠerences in physiological responses between the crime-relevant and irrelevant information. To examine the diŠerences in physiological responses, this study used the following four statistical values: Lykken's scores, likelihood ratios, eŠect sizes, and p values of randomization tests. A total of 152 participants, 80 of whom actually knew information related to a mock theft, received a CIT about the theft. From these CIT data, the four statistical values were calculated. On the basis of these values, whether each participant knew the theft-related information was ascertained. High correct discrimination ratios were seen for eŠect sizes (92.4) and p values of randomization tests (90.6) compared to Lykken's scores (83.2) and likelihood ratios (74.8). Areas under the receiver operating characteristic curves were also greater for eŠect sizes (0.919) and p values of randomization tests (0.928) than for the other statistical values. These results suggest that eŠect sizes and p values of randomization tests are promising for examining the physiological diŠerences in the CIT.
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