A ruling ordering Mark Grant to be retried for the 1984 slaying of teenager Candace Derksen is officially before Canada's top court.
Lawyers with the Manitoba Prosecutions Service filed a notice to appeal the Manitoba Court of Appeal ruling to the Supreme Court.
The Court of Appeal ordered Grant, 50, be given a new trial on the basis he wasn't given a full defence at his 2011 trial.
Derksen, 13, disappeared after school and was missing for weeks until her body was found tied up and frozen in a shed at a business near the Nairn Overpass.
Grant wasn't arrested until 2007 after cold-case investigators obtained DNA results from a private laboratory linking him to twine used to bind Derksen.
In 2012, a jury convicted him of second-degree murder and he was sentenced to life in prison.
A new trial was ordered Oct. 30 when the Court of Appeal found jurors were barred from hearing anything about a similar case in September 1985 when Grant was in custody on an unrelated matter.
Winnipeg police probed the case of a girl, 12, who was found tied up in a boxcar months after Derksen's body was found.
The complainant, now an adult, testified in 2011 and denied the event happened.
Grant's trial judge refused to allow his defence team to present details of that case to the jury. The Appeal Court disagreed with that decision.
Prosecutors will argue the move to overturn Grant's conviction and order a retrial was a legal error.
"The Manitoba Court of Appeal erred in overturning the learned trial judge's decision that the risk that admitting similar fact-based, third-party suspect evidence would prejudice the trial outweighed its probative value," the Crown's notice of appeal states.
Grant's defence lawyer, Saul Simmonds, has not responded to the Crown's application.
It will be up to a panel of three Supreme Court judges to decide whether to grant the Crown leave to appeal and push the case to a full hearing. If leave is denied, the Crown can either retry Grant for Derksen's killing or drop the case, meaning Grant would be freed.
He was returned to remand status in Manitoba from federal prison in mid-November.
Grant has yet to signal if he will apply for bail, which he has the right to at this stage.