A psychologist named Paul Dell became the center of controversy when he came forward after the arrest of Tom Donney for killing his nineteen-year-old daughter in North Carolina in 1987. Dell had read newspaper reports about Donney's apparent lapses of memory and he introduced himself to the defense counsel as a psychological expert on multiple personality syndrome. He suspected that Donney might be suffering from this and he wanted to evaluate the man.
After a clinical interview, Dell put Donney under hypnosis, which he videotaped. He seemed to get nine other personalities coming through, which he said were manifested by odd finger tapping. He also appeared to be coaching Donney to the effect that if those personalities did not come through, he'd be facing a probable guilty verdict. In other words, he gave Donney every good reason to pretend—-and did this while Donney was in a highly suggestible state.
Dell then testified on the stand that this was a clear case of a man who was not responsible for his actions because a personality named "Satan" had made him murder his daughter. First of all, it was hardly a clear case, and second, Dell's method of eliciting the "personalities" was highly questionable.
The jury didn't buy it and found Donney guilty.
One of the problems with this case, and many others, is that few professionals admit to the significant problems with using hypnosis. These include:
- the possibility that a recovered memory is incomplete, inaccurate, or based on some leading suggestion.
- the possibility of hypermnesia or confabulation—filling in the gaps with false material that supports the subject's self interest. (This happens often.)
- the possibility that hypnotized subjects may experience hypnotic recall, in which a posthypnotic suggestion of something that did not happen gets retroactively integrated into the subject's memory as if it did.
- the possibility that personal beliefs and prejudices may influence how an event was initially registered and/or how the person interprets it during recall.
- the possibility that trauma has shifted or changed a memory.
- the possibility of "memory hardening," which occurs when a false memory brought out through hypnosis seems so real that the subject develops false confidence in it.
- the possibility that people can lie while under hypnosis (and that's why polygraphs are sometimes used as a safeguard).
All of these problems have been documented in experiments, along with the realization that a false memory, once articulated, can be difficult to distinguish from genuine memories.
Unfortunately, jurists are generally unaware of these errors, and one study with college students showed that they tended to attribute a higher rate of accuracy to hypnotically refreshed testimony than is warranted by evidence.
There are also numerous problems with trusting memory. During the late eighties, many cases were brought to court—-and people were convicted—-based on "repressed memory" testimony. Helped along by mental health professionals, plaintiffs claimed that childhood sexual abuse was suppressed from consciousness through a memory filtering mechanism that worked via dissociation. The abuse was so traumatic that the victim could store the memory away for many years and not recall it until they were adults. They had personal injury claims, they said, even though the injury had happened many years in the past. Therapists who saw the signs claimed that they could bring the memories forth with hypnosis.
It wasn't long before other mental health practitioners demonstrated that "repressed memories" could be planted and manipulated, and some of the most high profile cases were soon discredited. The professional community became polarized over this issue, with those who had invested their careers on repressed memories defending their turf against those who distrusted the phenomenon entirely. To date there is no clear consensus, so "expert witnesses" are not offering scientifically-verified information.
So where do we stand now on using hypnosis in forensic settings?