Throughout the years gone by, hypnosis has been used in criminal investigations to help validate eyewitness testimony. The testimony given by a suspect, witness or victim has in the past been considered valid when hypnosis has been used and you can read more about this phenomena within the work of Sheehan and McConkey whose work entitled Forensic hypnosis: The application of ethical guidelines featured in the Handbook of clinical hypnosis by Kirsch et al (1993).
In those years gone by, due to the research evidence that was available at the time, hypnosis was given a great deal more credibility for its forensic validity that it deserved. More recent studies on the nature of memory have been discussed in depth here on this blog and in my evidence based hypnosis podcast, do go have a read and/or listen. As a result of the findings about the nature of memory being reconstructive, hypnosis now has much less value as an investigative tool for use in this forensic way.
There are those that believe hypnosis is useful as part of any investigative process. For example, Udolf (1983) believed that hypnosis can help to overcome distracting conscious factors such as fear, apprehension and confusion that may occur during an eyewitness testimony. The hypnosis is then thought to help revisit the memories unconsciously that may not have been easy to access due to this conscious distraction.
Additionally, others with the dual nature of mind (conscious and unconscious) theory underpinning their work, believed memories may have been repressed or escaped conscious detection – therefore hypnosis can be used to investigate if the unconscious mind picked it up or has access to anything repressed. Scheflin and Shapiro in 1989 and Kroger in 1977 stated this stance to be the case.
In fact, Kroger himself was involved in a high profile criminal case in the US when he hypnotised a bus driver to recall a registration number of a vehicle used by kidnappers. This evidence helped to prosecute the criminals who were duly convicted.
You can search the internet for past criminal cases that have been successful due to the inclusion of evidence obtained through hypnosis. Though this kind of evidence is not permissible today in the vast majority of the same places. In fact the subject today comes with its fair share of controversy today, and some previous convictions that used hypnosis are even attempting to overturn and appeal against their convictions as a result.
I wrote before on the subject of hypnosis and memory and so shall not duplicate that stuff here today, but I suggest you go read it. As far as forensic hypnosis goes, the debate has two sides; those that believe hypnosis can be used to elicit information from people and use that information for forensic purposes. They tend to think that hypnosis does not affect memory detrimentally. Then on the other side are those who believe hypnosis alters memory, that any individual who is hypnotised can willingly lie and be deceitful, and can also fill in gaps in their memories with their own imagination and fantasy, not to mention any potential leading by the interviewer/investigator.
Following a review of the literature and research, I think it important to know that memory can distort reality whether in or out of hypnosis. We have all noticed the different accounts of the same incident by a number of people – all perceiving it in their own way. However information is elicited, it needs to be evaluated and assessed and examined. If anyone is motivated to lie, or distort information, they’ll do it whether they are hypnotised or not.
This may lead people to think that hypnosis is not really useable in this forensic context. For this purpose of eyewitness testimony, I think hypnosis is no more valid than any other means of eliciting information and it certainly is no more reliable, so why use it for this kind of thing?
That said, hypnosis could of course be used in a forensic context to help overcome the trauma and/or stress of being involved in these kinds of criminal investigations. It could help people adopt a more useful mindset, to enhance the individual’s involvement in an investigation.
In 1993, Spiegel suggested that the current emotional state of a person who recalls details of a trauma must be considered and noted with regards to how it impacts the information given, so hypnosis used to aid the emotional stability and security of an individual can still help the process along.
I don’t think hypnosis is going to start featuring regularly on TV as an integral part of the CSI teams tools, and although I do think Sherlock Holmes would make a terrific hypnotist, I doubt he’d ever consider it neessary to validate the evidence he put together!