The Manitoba Court of Appeal ordered the new trial on Wednesday for Mark Edward Grant, ruling that the trial judge was wrong to deny Grant's lawyer the right to present evidence that Derksen might have been killed by someone else.
Derksen was 13 years old when she disappeared on her way home from school on Nov. 30, 1984.
Her frozen body was found, tied up with twine, on Jan. 17, 1985 — six weeks after she went missing — on the dirt floor of a storage shed in a brickyard about 500 metres from her family's East Kildonan home.
Grant was convicted of second-degree murder and sentenced in 2011 to life with no parole eligibility for at least 25 years.
Derksen's parents, Wilma and Cliff Derksen, said they thought they finally had closure in the case.
"I think the shock is there," Wilma Derksen told reporters outside their home.
"We expected all kinds of things, but not a retrial."
Charge based on DNA evidence
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 laboratory, 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 has spent nearly half his life behind bars for 23 offences.
However, he has repeatedly denied killing Derksen.
Grant's lawyer, Saul Simmonds, 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," Simmonds said.
"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."
The Crown has not yet decided whether to challenge the Court of Appeal decision, go ahead with a new trial or drop the case.
The Appeal Court's decision noted "the critical issue" of the refusal of the trial judge — Glenn Joyal, who is currently chief justice of Manitoba's Court of Queen's Bench — to let Grant's lawyer present evidence of an "alleged unknown third-party suspect."
"The accused wanted to present evidence to the jury that, while he was in custody, a strikingly similar incident had occurred some nine months after the murder of Candace Derksen," Justice Michel Monnin wrote on behalf of the three-member Appeal Court panel.
"The theory of the defence was that the person who had committed the most recent incident was also responsible for her murder."
The second girl, identified in the ruling only by the initials P.W., had been abducted in a similar fashion in September 1985.
A suspect was never arrested, but police reports presented to the trial judge during a pretrial hearing noted that "the modus operandi and other physical evidence suggested that the same person abducted both P.W. and Candace Derksen," according to the Appeal Court's decision.
The judge also had a statement from a woman who said she found P.W. bound and crying inside an empty railway boxcar located less than three kilometres from the area where Derksen's body was found.
However, the victim herself provided vague recollections years later about what happened, and she ultimately recanted her testimony.
Joyal concluded that he was not, "even on a balance of probabilities, able to conclude that the alleged offence happened."
Evidence is 'very relevant,' court rules
As a result, he did not allow details of the second abduction to be presented as evidence in Grant's trial — a move the Court of Appeal disagreed with.
"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," Monnin wrote.
"The exclusion of the evidence denied the accused the opportunity of placing before the jury the full answer he wanted to make."
Simmonds said Grant could not have carried out the second abduction because he was in custody by then.
"From our perspective, the similar act would have assisted in demonstrating that Mr. Grant was not guilty," Simmonds said.
Wilma Derksen said it seems unfair for the family to have to endure another trial.
"It just seems unreal and, in some ways, unfair. But we do understand that the process has to work, and we want the process to work," she said.
"I wish that I could believe that … there was real grounds, you know? It just seems [like] such a fruitless technicality that just doesn't make sense to us at this point."
Juror spoke with journalist
The Appeal Court also expressed concerns about contact that was made between a juror in Grant's trial and a Winnipeg Free Press reporter after the trial concluded.
The reporter and the juror met at a gathering at Cliff and Wilma Derksen's home after the trial, and the reporter included the juror's comments in a book he wrote about the case.
"I must state that I consider the juror's conduct and the invitation of the journalist to communicate with him to be both unwise and lacking in judgment on both their parts," Monnin wrote.
The court will have to determine at some point whether the actions of the juror and the reporter breached the jury secrecy rule under the Jury Act, Monnin added.
Read the Court of Appeal's decision: