Broadening the use of the concealed information test in the field

Abstract

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. Many people regard the polygraph as a deception detection technique. However, the polygraph using the concealed information test (CIT) does not aim to detect deception: rather, it aims to detect crime-relevant memory. The CIT can assess whether an examinee knows details of a crime, despite saying “I don't know.” The CIT also can provide clues about crime details that the investigative organization has not yet grasped. However, despite its effectiveness, the CIT is widely used only in Japan. In this article, we aim to address this situation and facilitate more active use of the CIT. We first introduce how Japanese polygraphers take advantage of the CIT. We then propose simple scoring methods and their possible thresholds, which can be easily applied in the field.