WINNIPEG -- Canada's highest court will hear arguments over a new trial that was ordered for a man convicted of killing a Manitoba teenager 30 years ago.

In October, the Manitoba Court of Appeal ordered the trial for Mark Grant in the 1984 death of Candace Derksen. The court said the original judge didn't consider some evidence that could cast doubt on Grant's guilt.

The Supreme Court of Canada has now granted Manitoba prosecutors leave to appeal that decision.

"Guess What? My prediction was correct," Cliff Derksen, the teen's father, wrote on Twitter shortly after the ruling was released Thursday. "Our case is going to the Supreme Court! Wow."

The news was bittersweet for Wilma Derksen, the victim's mother.

The Supreme Court hearing is an opportunity to explore some issues of national significance around DNA that arose at the trial and is better than immediately going to a new trial, she said.

"We're feeling a relief because the thought of it going to a retrial is just very disappointing," Derksen said. "It had been a good trial and to have it overturned was just a shock and didn't do it justice."

But the hearing also means the continuation of a nightmare that began 30 years ago with their daughter's death.

Derksen was 13 when she disappeared on her way home from school in November 1984. Her body was found six weeks later, bound and frozen, in a storage shed not far from her Winnipeg home. Grant wasn't charged until 2007 after numerous tests on a piece of twine used to bind the teen.

Those details are hard to revisit once again, Derksen said.

"We go through the sadness again that it isn't over," she said. "We as a family remain in kind of a public conversation which is tough sometimes. We are looking at the positive that, again, something good might come out of all of this. That's been our wish from the beginning."

Grant was convicted of second-degree murder and sentenced in 2011 to life with no parole eligibility for at least 25 years. He has repeatedly denied killing Derksen.

His lawyer appealed the conviction. He argued the trial judge was wrong to deny him the right to present evidence that Derksen might have been killed by someone else. Another girl had been abducted in a similar fashion nine months after Derksen's death when Grant was in custody.

"It seems to me that this evidence, which I view as very relevant, could provide the basis upon which a reasonable, properly instructed jury could acquit," Justice Michel Monnin wrote on behalf of the three-member Appeal Court panel last fall.

"The exclusion of the evidence denied the accused the opportunity of placing before the jury the full answer he wanted to make."

After the ruling, the Crown had the choice to ask leave to appeal to the Supreme Court, go ahead with a new trial or drop the case. Manitoba filed a notice of appeal in December saying prosecutors will argue the move to overturn Grant's conviction and order a retrial was a legal error.