In what his lawyers call an "unprecedented move" the B.C. Court of Appeal is allowing Phillip Tallio to file an appeal of his murder conviction — almost 34 years after the filing deadline passed.

Tallio's lawyers had argued new testing of DNA samples could show he was wrongfully convicted of a child murder.

That claim comes in previously sealed documents, released by the B.C. Court of Appeal.

If true, that would mean Phillip Tallio, who will turn 52 in December, has spent decades behind bars for a crime he didn't commit — more time served than other famous wrongfully convicted Canadian prisoners, such as Donald Marshall (11 years), David Milgaard (23 years) and Ivan Henry (27 years).

According to Tallio's lawyers, new evidence shows a second man — a now-dead close relative of the accused — might have been the real killer.

Publication ban lifted

Until now, the allegations were covered by a publication ban. But on Wednesday more than 800 pages of submissions and affidavits were made public following an order by B.C. Appeal Court Justice Elizabeth Bennett.

Tallio's lawyers were applying to appeal his conviction for second-degree murder more than three decades after the appeal deadline expired. They argued the documents should be released.

Friday morning, Justice Bennett granted the extension of time to file an appeal, stating, "In my view the interest of justice demand that Mr. Tallio be permitted to bring his application for further DNA testing and to go forward with this appeal generally."

One of Tallio's lawyers, Rachel Barsky, says the granting of the extension is unprecedented.

"This is a historic day in the world of criminal law and the world of wrongful convictions," says Barsky. "We've got a long road ahead. But this is truly a historic day. There's never been an extension of time that's been granted as long as today."

Tallio's daughter, 33-year-old Honey Hood, has only met her father once since he was jailed. She was in court for the decision.

"I instantly started crying tears of joy," says Hood. "I was so happy for him, because I know how much he's been struggling to be in there."

Tallio maintained innocence

Tallio was 17 when he was arrested in April 1983, accused of suffocating his cousin, 22-month-old Delavina Mack, during a drinking party in Bella Coola.

He originally pleaded not guilty. But nine days into his trial, his lawyers changed the plea to guilty.

Tallio, who is described as having an intellect "far below his years," didn't appeal within the required 30-day period, but he has maintained his innocence ever since.

Now 51, he has repeatedly been denied parole.

Eight years ago, his case caught the attention of the UBC Innocence Project, which according to its website "engages … a selected group of law students to review claims of wrongful conviction in British Columbia."

Some of those students are now fully fledged lawyers, representing Tallio.

'There is fresh evidence'

In the documents unsealed by the B.C. Court of Appeal, his legal team claims "there is fresh evidence" from a DNA test result that excludes Tallio as the killer, and provides information "leading to other possible perpetrators."

Tissue samples taken from the toddler were kept at B.C. Children's hospital. There was no DNA testing available when Tallio was convicted in 1984.

The imprisoned man's lawyers maintain a test for male DNA conducted in 2013 on one sample ruled out Tallio. A test on another sample, however, found Tallio "cannot be excluded" as a suspect.

Barsky says that simply means the second test was inconclusive, given the technology in use four years ago.

"'Cannot be excluded' doesn't mean a match," Barsky told CBC News. "We're dealing with a lot of missing information."

Tallio's uncle 'cannot be excluded'

Based on partial DNA, the killer could have been any male relative of Tallio.

His lawyers argue Tallio's paternal uncle, Cyril Tallio Sr., was also at the party where Mack was killed. His DNA was also tested, and he "cannot be excluded" as a suspect.

The legal submission adds: "Cyril Tallio had a criminal record related to sexually assaulting children." He died in 2014.

Phillip Tallio's lawyers want the court to order the release of the DNA samples held by the Crown for new testing, but so far, they say the Crown has refused, claiming the victim's family "has a privacy interest in the sample."

Now that the application to appeal his conviction has been allowed, there could be months of legal battles ahead over the DNA samples.

But Tallio's lawyers say the DNA must be re-examined for the sake of a man who may have been wrongfully imprisoned for more than three decades. Their submission before the B.C. Court of Appeal is blunt:

"These remaining samples provide the only possibility for DNA to prove Mr. Tallio's innocence."