Yves (Colossus) Plamondon was released from prison in January pending a new trial in April.
The Crown announced Thursday it accepted his acquittal on the first murder charge and was stopping proceedings on the two others.
The Crown said witnesses and investigators have died and evidence has been destroyed since the case was first heard back in the 1980s.
Plamondon, who spent 28 years behind bars, refused to admit his guilt — a necessary step for him to ask for conditional release.
The man, who is now 64, was sentenced in 1985 for three murders.
He was linked to the drug trade in the 1980s and was connected to the victims.
Plamondon left court Thursday looking visibly relieved.
"I'm very happy, it's over," he said, his voice tinged with emotion.
"It's something. I've been waiting 30 years for this. It's finished, it's finished."
Daniel Rock, his lawyer, said there will likely be further legal action on Plamondon's behalf.
"Obviously, there will be lawsuits concerning the harm he has suffered," Rock said.
"They relied on an informant who was completely crazy. We discovered afterward what he had received.
"The system of snitching is appalling."
Plamondon's lawyers began seeking his release in 2008, petitioning the federal Justice Department for a new hearing. That led to his release in January.
"They never wanted to concede anything," Rock said of the Crown.