Jacques Delisle said he left a loaded gun for Nicole Rainville to take her own life in November 2009 and tried to talk her out of it but that he didn't kill her.
The confession in interviews with "The Fifth Estate" and Radio-Canada's "Enquete" comes as Delisle embarks on a last-ditch direct appeal to Justice Minister Peter MacKay to review his case.
Delisle was found guilty of premeditated murder in 2012 in Rainville's slaying and has since lost at the Quebec Court of Appeal and the Supreme Court of Canada.
Now 79 and in a maximum-security prison north of Montreal, the former Quebec Court of Appeal justice told CBC and Radio-Canada what he didn't tell the jury — that his wife was set on taking her own life and that he left her the loaded weapon used in their death.
A news conference is scheduled for Friday morning in Quebec City to formally announce a direct appeal to MacKay.
When police arrived at the house, Delisle told them his wife had gone to get the gun by herself.
Asked in the interview why he lied, he replied: "Because I didn't want the family to know what really happened that morning. I didn't want the family to know I helped Nicole commit suicide."
When the time came to testify at his trial, he sent his lawyer, Jacques Larochelle, to tell his family the dark secret. They were devastated and the night before he was to take the stand, his daughter-in-law asked him to keep quiet.
He agreed, but says now he realizes it was a mistake.
Asked why he should be believed now, Delisle replied: "Because I am telling the truth today, it's as simple as that."
The Crown maintains the theory it had when the trial began in May 2012 in Quebec City: that Delisle killed his wife to begin a new life with Johanne Plamondon, his mistress and former secretary. The Crown argued that if Delisle ever divorced his wife, he'd forfeit more than $1 million in an eventual divorce settlement.
"He killed her in order to start a new life," Charles Levasseur, the prosecutor in the case," Levasseur said.
Larochelle, a veteran Quebec defence attorney, felt the forensic evidence was flimsy. But Delisle's decision to stay silent took the ball out of his hands at a crucial moment.
Delisle also felt confident and thought it impossible that a dozen jurors would find him responsible for an act he insists he did not commit.
His only hope now lies with the justice minister. According to the CBC, only two of 72 such requests have been granted in the past five years.
James Lockyer, an Ontario attorney and founder of the Association in Defence of the Wrongly Convicted, has taken up Delisle's case.
"I try and take on cases where I think the people I'm helping are genuinely innocent," Lockyer said. "And I think Mr. Delisle is genuinely innocent."
Lockyer said Delisle was convicted on what he qualified as poor forensic evidence, common in wrongful conviction cases.
Delisle believes he may have also been punished by the jury for having an extramarital affair with Plamondon.
"If it was one of their arguments, it's stupid, because I'm not the first person to have an extramarital affair in life," he said.
"No, that (the affair) wasn't a motive."
"I loved Nicole, I loved Madame Plamondon."