Question

Explain how a polygraph exam is presumed to detect deception. Discuss at least two strategies for administering a polygraph exam.

Answer 1

Detection of deception with the polygraph

The most widely used polygraph technique is known as the Control Question Test . In this type of test, the suspect answers several questions while connected to the polygraph. Among these questions are relevant and control questions. The relevant

questions specifically deal with the incident under investigation, for example “on the 25th of March, did you hold up the post office in Chorley?” The control questions have a more generic nature, but also deal with undesirable behavior, for example “In the first 25 years of your life, have you ever done anything illegal?” It is reasoned that the most threatening questions will elicit the strongest physiological responses. The crucial assumption is that the relevant questions are most threatening for guilty suspects, whereas the control questions form the biggest threat to innocent suspects. This latter assumption requires some explanation. A CQT is preceded by a lengthy interview that serves to convince the suspect that the polygraph can determine to an extremely high degree of accuracy determine whether the suspect is lying or not. This means that an innocent examinee can confidently and honestly answer “no” to the relevant questions. After all, the polygraph will show that this is the truth. Furthermore, the interview serves to maneuver the examinee into answering “no” to the control questions by suggesting that confessing illegal activities will negatively influence the test outcome. As a result, the innocent examinee is assumed to show the strongest physiological responses to the control questions, fearing that his/her deceptive answer to this question will get him/her convicted for the crime under investigation.