A Supreme Court of Canada ruling calling into question the reliability of confessions obtained during so-called Mr. Big sting operations could prompt the review of dozens of convictions, some legal experts say.

"I think there are going to be a number of cases where that’s going to have to happen because of the change of the law," said Peter Copeland, a criminal defence lawyer who has researched Mr. Big cases.

Any suspects nabbed under a Mr. Big sting who are currently facing charges or whose cases are still in the system, meaning they've been convicted but haven't exhausted their appeals, could be affected by this decision, Copeland said.

"Certainly for people whose cases are in the system, it’s a game changer," he said.

Mr. Big sting operations involve police posing as criminals in an attempt to obtain a confession from a suspect. Up to 2008, the tactic had been used at least 350 times to try and solve cold murder cases, court heard. The RCMP has said of the resulting prosecutions, 95 per cent had ended in convictions.

But on Thursday, the Supreme Court found that suspects often confess in Mr. Big operations "in the face of powerful inducements and sometimes veiled threats — and this raises the spectre of unreliable confessions."

"[The ruling] will certainly affect anyone who is about to be tried. It will also affect anyone who has been convicted and has an outstanding appeal," said Russell Silverstein, a lawyer for the Association in Defence of the Wrongly Convicted, which was an intervener in the case. 

The case centred around Nelson Hart, who was convicted in 2007 in Newfoundland of two counts of murder in the drowning deaths of his twin three-year-old daughters, based largely on his confession to undercover officers. His conviction was later overturned over the reliability of his confession and his case eventually ended up in the Supreme Court. One of Hart's lawyers, Jamie Merrigan, said Thursday that he expected his client would go free since, without the confession, there's not enough evidence for another trial

'A hook for release'

"Dozens, scores, maybe 100-plus pleaded not guilty and said 'I confessed because I was tricked,'" said Phillip Campbell, a lawyer for the Criminal Lawyers’ Association of Ontario, which was also an intervener in the case."How many of those have a factually plausible claim is hard to say, but some will. They will view this as a hook for release."

"There are a number that will deserve a fresh look and maybe have new life."

The Supreme Court decision placed stricter rules on the admissibility​ of such confessions, ruling that these types of confessions should be treated as "presumptively inadmissible" and that the onus is now placed on the crown to prove the admissibility of such confessions.

"I would say those people can invoke Hart and say their confessions would not have survived the analysis, especially the onus shifting to the Crown," said Campbell. "There are confessions out there that have supported convictions which are even less reliable than Nelson Hart's confession."

Those who have exhausted their appeals will have a more difficult path. They would have to make an application to Justice Minister Peter MacKay under section 690 of the Criminal Code, asking him to review their case as a potential miscarriage of justice.

"Particularly in a case where there was very little confirmation for the confession, I would not be embarrassed to bring an application to the minister saying you have to take another look at this confession [that] would not be admissible under these [new] standards," Campbell said.

"The core of this reasoning is unreliability. If you can come to the ministry with a convincing argument of unreliability, then in principle, you can succeed."

But Henry Reiner, a Crown counsel in British Columbia, said he doesn't believe many Mr. Big cases will be affected by this ruling.

"My expectation is that some defence counsel will try but I think they will be largely unsuccessful," he said. "I would think that unless there's something besides that, they would not get a new trial."

"If it's applied objectively I think it may not affect most cases now in the system."

Reiner said the Hart case was problematic and that a lot of prosecutors would not have run that case.

"You never wanted to run a Mr. Big case unless there was a lot of corroboration​ confirming that the confession was true," he said. "You should start from the predicate that this confession is not true and look for evidence that it is in fact true."

A case shouldn't be hung on just the confession of the suspect, he said, adding that every Mr. Big case he prosecuted had lots of corroboration​ and confirmatory evidence.

"I'm confident if they were to be reviewed, there is such a wealth of confirmatory detail tending to confirm the validity of the confession."

Supreme Court ruling in Hart case

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With files from The Canadian Press