One of the ironies of criminology is the unreliable nature of eyewitness testimony. So many convictions obtained on the basis of eyewitness testimony have been later overturned, whether on the basis of DNA evidence or other indices demonstrating that the accused simply could not have committed the crime, and yet the eyewitnesses believe that they are telling the truth. Forensic interviewing becomes a crucial element of the investigation process, as the questioners have to decide whether or not the information they have elicited is as accurate as possible.
The cognitive interview takes the point of view of the eyewitness and uses a number of different techniques to try and elicit information about the time the interviewee is trying to remember. Sometimes these techniques include helping the interviewee mentally rebuild the context of the crime or of seeing the suspects; sometimes they are asked to describe things from a different point of view, as from the point of the view of the criminals themselves or from other witnesses; sometimes they are just asked to recount every detail (McLeod 2010). Among the choices of a polygraph and a course of hypnosis, this seems like the most valid.
While hypnosis has yielded some significant results, it is important to remember that there is still no clinical agreement as to what is actually going on during hypnosis – or what hypnosis actually involves (Harary 1992). There is no standard about the procedures used to bring about a hypnotic state, and there is no way to know, conclusively, that a person is actually going through hypnosis. Researchers are pursuing some sort of quantifiable state in which people suddenly have access to their unconscious and can remember the crucial information for the interview at hand. Sometimes the hypnotic technique works, but given the lack of standardization for the process, it is difficult to argue its superiority over either the cognitive interview or the polygraph.
The polygraph might seem like the gold standard of interviews. After all, there is a scientific basis for comparing physiological responses when a person is being truthful and when a person is telling a lie (or at least bending the truth enough to awaken the body’s responses). Despite the fact that there has not been enough scientific support for the widespread use of the polygraph – even in 2016, it remains inadmissible for use in the courtroom – it has gained enough acceptance that law enforcement and intelligence personnel value it most highly when identifying criminals in a case (Faigman, Fienberg & Stern 2003). The fact that scientific studies are still wanting, after all this time, for its validity, suggest that the cognitive interview might still be the best of the three choices.
Eliciting information in a criminal investigation is a difficult process even for the best of detectives. Each of these three types of interviews has its advantages and its drawbacks. There are cases in which each interview type has shown its promise, but overall, cognitive interviewing appears to have fewer areas of potential invalidity than the other two. For now, it makes sense to proceed with that one until researchers can find ways to make polygraphs more verifiably valid and to identify standard processes and procedures for hypnosis. Without more scientific validity, it is impossible to recommend other methods.
References
Faigman, D., Fienberg, S. & Stern, P. (2003). The limits of the polygraph. Issues in
Science and Technology. http://issues.org/20-1/faigman/
Harary, K. (1992). The trouble with hypnosis. Psychology Today.
https://www.psychologytoday.com/articles/200910/the-trouble-hypnosis
McLeod, S. (2010). Cognitive interview. Simply Psychology.
http://www.simplypsychology.org/cognitive-interview.html
