The Taint of Post-Hypnosis Evidence and the Fallibility of Memory (R v. Trochym)

If there are any forensic hypnotists who work solely on criminal investigations, they may find themselves out of work following the Supreme Court of Canada’s (“SCC”) recent decision in R. v. Trochym, [2007] 1 SCR 239 [Trochym]. Prior to this decision, Canadian courts had generally allowed the admission of evidence by witnesses whose memories had been refreshed through hypnosis as long as the trial judge found that such evidence was sufficiently reliable through a voir dire.

In Trochym, the majority of the SCC reversed this practice and held that all testimony by a witness on matters covered during hypnosis is absolutely inadmissible. This includes any new memories or details recovered by a witness through the procedure. However, this exclusion also applies to memories that a witness may have had before hypnosis if they are brought up during the hypnosis. Even evidence that is not covered within the hypnosis session will be subject to increased judicial scrutiny and, if admitted, must be accompanied by cautionary words to the jury. Due to the trial judge’s error in admitting post-hypnosis evidence (inter alia), the majority set aside the conviction and ordered a new trial.

In coming to this result, the majority examined expert evidence on hypnosis found in several American cases. The majority used this evidence by applying the test for “novel sciences” developed in R. v. J.-L.J., 2000 SCC 51 and came to the conclusion that forensic hypnosis is not sufficiently reliable as a science to allow the admission of post-hypnosis evidence. The dissenting judgment criticized this approach and accused the majority of taking judicial notice of expert evidence without granting the Crown a chance to present contrary evidence or to directly cross-examine any experts. The dissent held that there was not a sufficient evidentiary foundation for the majority to overturn the long-standing admissibility rule on hypnosis. Further, the dissent held that the use of forensic hypnosis in refreshing memory was a well-established field that should not be subject to the same test used to determine the admissibility of expert evidence in a “novel science.”

While these technical issues may have significant consequences for the continued admissibility of established scientific evidence, the truly striking issue that emerges from the SCC’s discussion is not on the reliability of hypnosis, but the reliability of memory itself.

As the majority noted, the general consensus within the scientific community is that “memory does not work like a tape recorder that can be played back but, rather, is constructive or additive.” Thus, the very act of remembering is much more of a “creative mental process” than is generally thought. Witnesses recall small details and attempt to piece them together in a way that makes sense. It appears that the effect of hypnosis is to magnify a person’s memory. Under hypnosis, a person has an increased ability to recall the details of their memories, which may include both accurate and inaccurate information.

Thus, it appears that while there is no guarantee as to the accuracy of memories that have been hypnotically refreshed, such evidence may be no more or less accurate than ordinary memories. This was the view taken by the dissent:

“A witness who testifies from ordinary memory a year and a half after seeing a crime, may inadvertently incorporate facts he gleaned from the media or others into their recall. There is no guarantee with respect to the accuracy of such ordinary memories either. Judges know these risks, yet we do not deem such evidence inadmissible. These sorts of potential frailties with memory, whether ordinary or hypnotically refreshed, are those that we have always assumed juries are quite capable of weighing.”

As the dissent notes, it would be unreasonable to expect hypnotically refreshed memories to be more reliable than regular memories. With proper safeguards in place to avoid possible suggestion or contamination of a witness’s memory, hypnotically refreshed memories should be allowed as evidence. Indeed, there does not appear to be a substantial difference between memory refreshed from hypnosis and refreshed memory from a different source, such as an object or a song. In both cases, the witness uses details that are not readily available to their minds in order to trigger a present memory of the event that may or may not be accurate. Potential problems created by the means of refreshing the memory could still go to weight.

In contrast, the majority focused on the increased risks of unreliability that may arise from hypnosis. First, there is a risk of confabulation, or the creation of false memories, either through suggestion or because of an unconscious desire to compensate for a lack of actual memory. Second, there may be a decreased critical faculty to filter out information inaccurate information during hypnosis. Finally, there is a “memory hardening” whereby a person who has been hypnotized becomes “increasingly, and unduly, confident in his or her memories”. Still, the majority did recognize that these risks were also present for ordinary testimonial evidence as well.

Interestingly, both the majority and the dissent discussed at some length the inherent fallibility of human memory in their judgments. While the majority raised such concerns to emphasize the need to more careful with post-hypnosis evidence, the minority pointed to the equal reliability (or unreliability) of memory, both ordinary and hypnotically refreshed, in holding that the latter should be admissible. But the elephant in the room, of course, is the question of why we trust regular testimonial evidence, based on memories, so that it is generally admitted when it too is based on the fallible “creative mental process” of remembering. Perhaps, in certain circumstances, even regular testimonial evidence may so lack requisite safeguards as to reliability that it too should be inadmissible and never go to the trier of fact. Further study may be needed to learn the reasons why some memories are faultier than others.

While there may be some cause for concern regarding the reliability of post-hypnosis evidence, the majority’s overly cautious approach throws out the baby with the bathwater. The blanket ban on evidence from all topics covered during hypnosis appears overly broad and would prohibit a witness from repeating statements at trial that were made to the police even prior to hypnosis.

In Trochym, a witness had given initial statements to the police that she had seen the accused leaving the victim’s apartment after the date of the murder but was unsure whether it was on Wednesday or Thursday. After hypnosis, she recalled that it was on Wednesday, which supported the Crown’s theory that the accused had returned to the victim’s apartment several hours after the murder in order to stage the crime scene. But as the dissent noted, this evidence is highly probative for the Crown regardless of which day it had occurred because it shows that the accused had returned to the victim’s apartment after the victim had been brutally murdered, contrary to his testimony. Further, it shows that he had likely seen the victim’s corpse in the apartment and knew of her murder but took no action. But at the new trial ordered by the majority judgment, the witness will not be allowed to give evidence that she even saw the accused at the apartment after the date of the murder, although this was part of her initial statements to the police prior to the hypnosis.

Further, as Justice Charron noted in her concurring judgment, the majority did not offer any good reason why a witnesss testimony regarding topics not covered during hypnosis should be subject to increased judicial scrutiny. The majority did not offer any scientific evidence to show the possibility that hypnosis which covers one topic could affect the reliability of a person’s memory of a different subject. Thus, at the new trial in this case, evidence from this same witness about hearing someone banging on the victim’s door and being allowed to enter on the night of the murder may not be admissible even though the witness was not uncertain about this point and it was not subject to hypnosis. Even if this evidence is admitted, it would be mandatory that the trial judge provide the jury with special instructions regarding the possible tainting of this evidence by the hypnosis procedure.

If the witness had not undergone hypnosis, it is clear that she would have been allowed to provide evidence on both of these points. And if the judge had restricted her evidence to that contained in her initial police statements, the witness’s evidence would have been exactly the same as that which she would have provided prior to hypnosis. While there may be some practical difficulties in limiting her testimony to that contained in her original account, particularly during cross-examination, such problems often arise any time evidence is partially excluded, such as when it is only allowed for a limited purpose. As Justice Charron stated in her concurring judgment, the majority’s approach “overshoots the underlying purpose for excluding post-hypnotic memories.”

One other concern arises from the SCC’s ruling. The majority stated that while post-hypnosis evidence is inadmissible in court, other uses of hypnosis are not prohibited. They provided the polygraph test as an example of a scientific technique that might not be admissible as evidence in court but might still be helpful to police in their investigation. The difference is that only the results of a polygraph test are inadmissible; a person who undergoes such a test can still testify at trial. In a situation where a witness may, under hypnosis, be able to provide information to help identify a suspect, such information may never be obtained because the police and the Crown will now be very wary of using the procedure for fear that it will taint all evidence by that witness.