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Applicability and Ethicity of Behavioral Lie Detection

© Michael Decaire

In the past I have presented a few editorials on behavioral (non-verbal) lie detection. I have also tought some undergraduate introductory courses on the topic, and most recently been asked for permission to reprint an article I wrote for inclusion in the teaching materials of a major deception-detection training program. The topic appears to be very popular.

Many of the proponents of non-verbal behavioral lie detection consider the discovery of these queues of deception the holy grail of investigative psychology. The opponents consider it a highly unethical bastardization of psychology. I am going to take a bit of time aside this month to give my views on the state of such interviewing.

There is definitely a fairly large group that considers the practice of behavioral interrogation a significant advance in criminal investigation. They believe the practice can accurately detect deception at a rate greater then other mechanisms of detection, that the practice can and should be used to bring forth a confession, and that psychological ethics should stay out of the interrogation room.

The effectiveness of the deception interview in detecting deception has been shown in the past to be superior to other commonly used methods. One must understand that judgements such as those made in the court regarding guilt can not, and never would, be based on the deception detection component of an interview. While the methods, when applied appropriately, are less prone to false positives, it is no sure fire method to prove guilt. The clues of deception are based on stress. The interrogation, whether applied to a guilty or non-guilty individual, is a stress full situation. For that reason the cues should be used as clues that allow an interrogator to guide the interview, not as a method of assessing guilt.

One must critically evaluate where the interview is going to be guided. What is the ultimate goal of the deception detection behavioral interview. Many proponents (and guidebooks on interview methodology as well) state that the goal is to elicit a confession. While I would agree that the goal of any police interview with a suspect they believe to be guilty is to elicit a confession, the use of behavioral interviewing should be distinctly separated from that process. The use of psychological knowledge in interviewing should be a relatively passive one. The realization that an area should be probed for further information and errors in continuity may be ethical. However, the use of psychological manipulation to elicit a confession most certainly is not. The practice of increasing a rooms temperature to apply physiological stress for example is clearly a unethical practice. While some may say that these processes are a necessary evil, I would argue that it is not one that would stand up in a court. As it is clearly a violation of ones rights.