Monday, February 05, 2007

A step forward for skepticism in Canada

Spotted this front-page article in the Toronto Star the other day. Apparently Canada's Supreme Court has placed a complete ban on evidence obtained through hypnosis being used in courts. (Full article here.)

In a 6-3 ruling that will have broad implications, the Supreme Court of Canada said the 30-year practice of using evidence obtained from witnesses who have been hypnotized is unreliable and should not be allowed in criminal trials.

The split decision appears to make Canada the first country with an English criminal-law tradition to place a total ban on post-hypnotic evidence.

Britain, Australia and New Zealand don't rule it out, although they impose procedural safeguards. The rules in the U.S. vary from state to state.

The decision overturns the second-degree murder conviction of Stephen Trochym, a former Canada Post supervisor from Toronto who was found guilty in 1995 of slashing his girlfriend's throat with a breadknife. The decision calls for a new trial.

Key evidence in the case came from a neighbour who said, after being hypnotized, that she remembered seeing Trochym emerge from the victim's apartment the day after the slaying in 1992.

The witness first told police she saw Trochym emerging from Donna Hunter's apartment on a Thursday, but changed her statement to Wednesday after undergoing hypnosis to refresh her memories. That timing corresponded to the police's theory of how the killer may have returned to Hunter's apartment to rearrange her body and make it look like a sexual assault.


Let's look at a few facts here:

1. Hypnosis is highly dependant on the attitude and expectations of the subject. People who believe hypnosis is impossible can never be hypnotized, for instance.

2. Hypnosis puts people into a highly suggestible state, and it's in fact something people do to themselves. They willingly turn off their free will temporarily.

3. There is no evidence that hypnosis helps at all in recovering memories. If you think of the mind like a computer, this should be obvious: Memory that's been deleted and overwritten cannot be re-obtained. It can, however, be rewritten from guesswork and suggestions of the hypnotist.

4. The witness originally claimed she'd seen the man on a Wednesday.

5. After police came up with the theory that he'd returned to the apartment on a Thursday, she went under hypnosis to "refresh" her memory. The goal was to see if she was in fact mistaken and it was a Thursday.

Put it together. No evidence hypnosis helps with memory, but it does make people suggestible. She was being asked questions by people who wanted her to think it was a Thursday, and thus under hypnosis said what they wanted her to say. You can see what the problem is with hypnosis, and thankfully, the Supreme Court did too.

The dissent to this ruling was described as follows:

But in a strong dissenting ruling, Justices Michel Bastarache, Rosalie Abella and Marshall Rothstein took the majority to task. "The sole evidence advanced before this court on the hypnosis issue was a handful of American cases in which the courts have opted for categorical exclusion. This is not a sufficient evidentiary foundation upon which this court should overturn a longstanding Canadian common law rule."

They said Trochym and his lawyers did not challenge hypnosis at the trial level, and there was not a strong enough factual basis to warrant the elimination of such a tool, especially since, as with other kinds of evidence, trial judges and juries can be alerted to its weaknesses.

"These sorts of potential frailties with memory, whether ordinary or hypnotically refreshed, are those that juries are quite capable of weighing."

The dissenting judges noted hypnosis is not exactly "novel science," having been used for 30 years to help memory retrieval. It is rarely admitted in court without a judge first assessing its relevance and reliability, and like other scientific evidence can always be assessed "through a case-by-case evaluation, in light of the changing nature of our scientific knowledge."


Allow me to perform a little magic trick here:

The dissenting judges noted pseudoscience is not exactly "novel science," having been used for 30 years to help obtain evidence. It is rarely admitted in court without a judge first assessing its relevance and reliability, and like other scientific evidence can always be assessed "through a case-by-case evaluation, in light of the changing nature of our scientific knowledge."


See the problem? Pseudoscience of many forms sneaks past judges all too often. They're legal experts, not experts on the philosophy of science (the fancy term for a skeptic). Many do obtain training in distinguishing good science from bad, but it's rarely sufficient. There are also no filters to make sure true-believer judges don't slip through. Juries are even worse off, as they'll likely have no training at all in this area.

The only solution is to simply ban a procedure from the courtrooms if it can't be shown to be scientifically effective. Otherwise, we risk letting false information sneak in under the guise of evidence, and letting the judge and jury buy it. Sometimes the government has to do the thinking for its constituents.

2 comments:

austinatheist said...

Sky rockets in flight! Afternoon delight...

Anonymous said...

Well this ruling should help put an end to people being persecuted by false memory syndrome cases. OTOH this same court just revived the idea of debtor's prisons (but only if the debt is to an ex-wife).


I've sat in a courtroom while a mother was trying to explain to a judge that feeding a child sweet fruit was not like feeding a child white sugar or choclate bars - why this came up isn't really relevent but it was important at the time.

The judge interrupted her, saying "sugar is sugar", and wouldn't let her finish. Any doctor, any nutritionist and many average parents could have told him how wrong he was but he considered himself an authority. And judges want to decide what science is admissable on a case by case basis? [shudder....]