On December 18. 2019 Dr. Orthey and a group of students from the Kwansei Gakuin University psychophysiological laboratory of professor Katayama were invited to the forensic lab of Nara prefectural police headquarters to discuss the application psychophysiology techniques in the criminal investigation.

In Japan, the police applies the Concealed Information Test (CIT) to detect if a suspect has knowledge about a criminal event that only the real perpetrator can know. During our visit a police polygrapher demonstrated the first step of the CIT examination, the so called “card test”, on one of our students. In this procedure, the suspect picks one of five playing cards and hides their knowledge of this card. Next, the police polygrapher presents all five answer alternatives one by one while the student rejects all of them.

During this procedure the forensic examiner records several psychophysiological indices of the autonomous nervous system such as sweat, here measured as Skin Conductance Level (SCL) and Skin Conductance Response (SCR).

Below we can see the responses of our student when confronted with the different possibilities. Look at the SCR responses, can you guess which number was printed on his card?



Research has shown that the correct answer elicits a larger SCR response than the other answer alternatives. Theoretically, this elevated response is a consequence of the memory recognition process. Here our student drew a card with the number six on it (Q4). If an examinee was unaware of the correct answer, we would expect a similar response to all answer alternatives.

After the demonstration, our host Mr. Bito gave a presentation on the benefits of a CIT examination which are not already known outside the police to prevent mistaken arrests and false charges in a criminal investigation.

According to him, material evidence can link a suspect to a location or object leading to a hypothetical story detailing the crime event. However, this does not always automatically mean that the suspect is the perpetrator and a false confession could occur. Mr. Bito proposes that the CIT preceding the interview can serves as an additional check to confirm the “story” told by the evidence. In this case a suspect would be tested for factual knowledge about the crime inferred from the physical evidence, and an absence of memory recognition for details of the story would cast doubt on the validity of any confession. However, the CIT cannot be used for this purpose once a suspect has already confessed, because at this point it cannot be excluded that the suspect acquired the information from the confession during the interview. Hence, this type of CIT can only be used after a confession was obtained if the police still holds information only the perpetrator can know, but that was not revealed during the interview.

The CIT is an integral part of the criminal investigation in Japan and therefore the study of psycholophysiological techniques is a valuable endeavor to introduce scientifically validated methodology to real life applications. Similarly, the scientific study of the CIT is an active field devoted to the development of novel indices or paradigms and further improvements of the CIT procedure.