Peter Foster claims the daughter of accused wife killer John Chardon tried to hire a hit man to kill the convicted conman over his involvement in her father's murder case.
The explosive allegation was one of several Foster made on the opening day of the Gold Coast businessman's committal hearing on Wednesday.
Recruited by police in 2015 to help extract information from Chardon about the disappearance of his wife Novy two years earlier, Foster repeatedly told Brisbane Magistrates Court there hadn't been anything in it for him.
"Whilst I think he is a very dangerous man and I think he murdered his wife, and playing Sherlock Holmes I think he probably killed his first wife as well," he said.
"There's no amount of money that you would wrongfully convict anybody, I mean you just simply don't do it."
He added he had no evidence to support his claims about Chardon's first wife and could be wrong.
Foster, who is on remand in a NSW jail, claimed he was finally trying to do right and that someone needed to speak for Novy.
But he conceded he had asked himself as recently as Wednesday morning if he was risking his life by giving evidence.
"The reason I say that ... is the Queensland police came to me two years ago and said they had intel Mr Chardon's daughter was trying to get a hit man to kill me and did I want witness protection?" he claimed.
Foster said over the past three years he kept thinking what his idol, rugby league coach Wayne Bennett, would do.
"I always thought what would coach Bennett do and I thought at this time, coach Bennett would say, 'you tell the truth and you do your civic duty' and that's why I'm here," he said.
He said he also understood his history of conning people made him difficult to believe.
The court heard Foster contacted police after a TV broadcast about a search for Novy's body watched by the two men where they were both incarcerated.
Foster claimed after telling Chardon about the segment, the accused killer said, 'well they won't find her there', before he got his lunch and called his lawyer.
"He didn't seem at all perturbed," he said.
"If you didn't have anything to do with your wife's disappearance, you would just be sitting glued to the TV."
The court heard Foster agreed to be an informant and move into Chardon's cell.
"To my complete stupidity I said to them 'I only need a couple days with him, let me just get close to him for two or three days'," he said.
"It took six weeks overall and it was the worst six weeks of my life."
Foster said he asked police to get him a listening device because he didn't think anyone would believe his account.
The hearing continues.