TORONTO -- The longest-serving inmate in Canada to have a murder conviction quashed can sue those involved in his prosecution, Ontario's top court ruled Thursday.

In its ruling, the Ontario Court of Appeal said it would be wrong to deny Romeo Phillion, who spent 31 years behind bars protesting his innocence, a chance at a civil lawsuit.

In essence, the court found, the issues Phillion wants to litigate are different from what the Appeal Court looked at when it overturned his conviction in 2009 and ordered a new trial on the grounds that police and Crown had failed to disclose a crucial piece of evidence.

"The stakes, purpose and process were entirely different from this civil action," the Appeal Court said.

"In any event, the findings made on the reference with respect to the conduct of the Crown and police did not consider any issues of negligence or a common law duty of care as alleged in the statement of claim."

Phillion was convicted of second-degree murder in 1972 in the death of Ottawa firefighter Leopold Roy five years earlier based on a confession he recanted almost immediately. He was jailed for life and unsuccessfully appealed all the way to the Supreme Court of Canada. He always refused to seek parole, saying it would amount to an admission of guilt.

However, he was ultimately able to persuade the federal government to refer the case to the Ontario Court of Appeal, which quashed his conviction and ordered a new trial in 2009. The court found that police had initially verified an alibi showing Phillion's innocence but never told the defence about it, apparently because investigators subsequently debunked the alibi.

The Crown withdrew the charge, arguing too much time had passed to pursue a new trial.

Phillion, now in his mid-70s, then sued for $14 million, alleging negligence and wrongdoing by prosecutors and two Ottawa police officers. In April last year, Ontario Superior Court Justice Eva Frank decided the suit would be an abuse of process and should not proceed.

In her ruling, Frank said the Appeal Court had already rejected suggestions of wrongdoing by police or Crown and that too much time had passed to try Phillion's claim now.

However, Thursday's decision found several problems with Frank's reasoning.

Phillion should not be blamed that so much time has passed, Appeal Court Justice Kathryn Feldman wrote in the unanimous judgment.

"Whether wrongfully or not, it was the respondents who had the knowledge of the information that led to the (Appeal Court) reference, to the setting aside of the verdict, and to the eventual withdrawal of the charge," Feldman said.

"To in effect punish the appellant for the passage of time in these circumstances by staying his action strikes me as manifestly unfair."

Phillion will now have to impugn the integrity of police and prosecution, something that was not required when he sought to have his guilty verdict set aside, Feldman said.

"It would further bring the administration of justice into disrepute to grant a stay in these circumstances and deprive the appellant of any opportunity to seek financial redress for his conviction when he did not have the opportunity to present a full defence at his trial."

Phillion's lawyer, David Robins, said from Windsor, Ont., on Thursday that his client was "pleased" with the decision and the lawsuit would now proceed.

It was not immediately clear whether there would be a further attempt at an appeal.