On Memory: Hypnotically refreshed memory

On Memory: Hypnotically refreshed memory

Shannon Kari, National Post Published: Monday, December 21, 2009

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A photo shows skull and brain with the help of double exposure. Memory is a complicated and misunderstood function of our brains.

David Barlow/AFPA photo shows skull and brain with the help of double exposure. Memory is a complicated and misunderstood function of our brains.

Case 1: Hypnosis

One of the best known cases where hypnosis played a key role in a Canadian trial was the original prosecution of Robert Baltovich.

The Toronto man was convicted in 1992 of second-degree murder in the death of his girlfriend, Elizabeth Bain. Four Crown witnesses were hypnotized and the supposedly improved memory of sightings of Mr. Baltovich by three of them were essential to the prosecution's case.

Mr. Baltovich spent nearly nine years in prison and the Ontario Court of Appeal overturned his conviction in 2004 and ordered a new trial.

By the time of his re-trial, early in 2008, however, the legal landscape had changed dramatically when it came to the use of hypnosis as a tool for refreshing the memory of witnesses.

The Supreme Court of Canada ruled in February 2007 that post-hypnosis evidence was presumptively inadmissible, because of concerns that it was essentially junk science. The ruling came in ordering a new trial for Stephen Trochym, a Canada Post employee convicted of killing his girlfriend.

Questions about the accuracy of hypnosis were raised as far back as the early 1980s. As a result of a 1984 ruling in Alberta, courts tended to admit post-hypnosis evidence as long as police followed certain guidelines aimed at ensuring the hypnotist was independent and did not put improper suggestions to the witness.

In its 2007 ruling, the Supreme Court looked to ongoing research about post-hypnosis evidence and the increasing skepticism about the practice, especially in the United States.

"There is a general consensus that most individuals are more suggestible under hypnosis, that any increase in accurate memories during hypnosis is accompanied by an increase in inaccurate memories, that hypnosis may compromise the subject's ability to distinguish memory from imagination, and that subjects frequently report being more certain of the content of post-hypnosis memories, regardless of their accuracy," wrote Justice Marie Deschamps for the majority. "While it is not generally accepted that hypnosis always produces unreliable memories, neither is it clear when hypnosis results in pseudo-memories or how a witness, scientist or trier of fact might distinguish between fabricated and accurate memories," she added. "This technique and its impact on human memory are not understood well enough for post-hypnosis testimony to be sufficiently reliable to be used in a court of law."

After several weeks of pre-trial legal arguments in the Baltovich re-trial, the Crown ultimately decided to call no evidence and Mr. Baltovich was acquitted of murder in April 2008.

Case 2: The Repressed memory

The use of so-called "recovered memory therapy" to unearth repressed memories of traumatic childhood events gained much favour in the 1980s and 1990s. It led to dozens of cases across North America where people were charged in cases of alleged historical sexual assault, usually of children. In some cases, the allegations included bizarre claims of satanic rituals.

Along with the use of hypnosis to prompt someone's memory, this practice is now treated with extreme caution by the courts in Canada. "I think it has pretty much been discredited," said Stephen Lindsay, a psychology professor at the University of Victoria, who has conducted research in this area.

The fundamental criticism of the technique was that therapists made too many suggestions that induced patients into believing certain traumatic events had occurred in their past.

"We don't remember anything without cues," Prof. Lindsay said.

"I don't buy the notion of repression. We simply forget a lot. I think we forget most of our lives."

While an individual may be more likely to remember a traumatic event in their past, they may also be "motivated to forget bad things" and simply not think about it, he explained. In testing the accuracy of these kinds of memories, he said it is crucial to examine "how did the person come to remember this."

Case 3: Guidelines for photo lineups

Sequential lineups: Photos of suspects should be presented one at a time, instead of in array of 12 presented as a group. Otherwise, witnesses are more likely to compare all 12 at once to see who looks most like the suspect.

Videotaping lineup identifications: This ensures that there is an accurate record of what takes place when a witness is asked by police to see if a suspect can be identified.

Pre-lineup instructions: Witnesses should be told the suspect may not be in the lineup. This lowers the chance of a witness feeling obligated to pick someone out of the lineup who most looks like the person they remember.

Use of fillers: Only one suspect should be included in a photo lineup. The rest should be "fillers," people known to be innocent, yet who fit the general description of the suspect.