The Appeal Court ruled that the trial judge was wrong to deny Mark Edward Grant's lawyer the right to present evidence that Candace 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.
"The exclusion of the evidence denied the accused the opportunity of placing before the jury the full answer he wanted to make."
Grant was convicted of second-degree murder and sentenced in 2011 to life with no parole eligibility for at least 25 years.
Derksen was 13 years old when she disappeared on her way home from school. Her body was found six weeks later, bound and frozen, in a storage shed.
Her parents, Wilma and Cliff Derksen, were surprised by the ruling.
"We're kind of shocked and in chaos," Wilma Derksen said outside her home.
"There's a kind of ... tragedy or comedy about it. It's just tough."
Cliff Derksen said the family felt certain that Grant was the killer.
"If there's any doubt, then it needs to be clarified, for sure. I guess we thought there wouldn't be doubt, but apparently there is."
The case against Grant hinged on DNA evidence from hair and fibre samples collected in the shed.
RCMP tested the twine used to bind Derksen in 2001, but results were inconclusive. A private lab, Molecular World in Thunder Bay, Ont., tested the twine and hair again in 2007. It was after that test that Grant was charged.
Grant, who is now 49, has a long criminal history. He spent nearly half his life behind bars for 23 offences. But he repeatedly denied killing Derksen. His lawyer suggested the Crown might think twice about whether to pursue a new trial, given the Appeal Court ruling on the possibility of another killer.
"To not be able to put that before a jury was, from our perspective, a significant blow to our defence," Saul Simmonds said Wednesday.
"It's our hope that maybe the Crown will take the time now to review the case ... and make a determination as to whether or not there will be another prosecution."
Simmonds told court at the time that Grant had a tortured childhood, had been abused by his father and had lived on the streets during his teenage years.
The Crown has not yet decided whether to challenge the Appeal Court ruling, go ahead with a new trial or drop the case.
Wilma Derksen said she and her husband can still feel their daughter's presence, even though decades have gone by.
"She comes, even after all this time, she's here. That means we're alive though.
"We'll make it."