Katherine Quinn was convicted in 2007 of the second-degree murder of Matthew Martins and received an automatic life sentence. (CBC)

The B.C. Court of Appeal has ordered a new trial for Katherine Quinn, who was convicted of second-degree murder in the July 2005 killing of a teenager at a SkyTrain station in Surrey, B.C.

The court overturned Quinn's conviction Friday, saying the trial judge erred in his instructions to the jury.

The panel of three appeal judges, led by Chief Justice Lance Finch, unanimously agreed to order a new trial for Quinn, who launched her appeal in March. A new court date has not been set.

Quinn, now 26, and her boyfriend, Robert Forslund, now 30, were found guilty of the second-degree murder of Matthew Martins, 16. They received automatic life sentences in April 2007, with eligibility of parole in 10 years for Quinn and in 17 years for Forslund, who did not appeal his conviction.

'To have to sit through a trial, it's the most painful thing any person can go through. But to have to do it a second time, it's excruciating.'— Sandra Martins-Toner, victim's mother

During the trial, the prosecution alleged that Quinn jumped Martins at the Surrey Central SkyTrain station and tried to steal his necklace. While she didn't take part in the actual beating of the victim, she allegedly gave Forslund the command to kill by saying, "If you love me, you'll kill him," the court heard.

Martins was thrown into a Plexiglas wall, kicked, had his head stomped on and his throat cut with a beer bottle, the court heard.

Friday's ruling, mostly written by Finch, said the trial judge failed to instruct the jury on the issue of whether Quinn abetted the murder.

Martins was thrown into a Plexiglas wall, kicked, had his head stomped on and his throat cut with a beer bottle, the court heard. (CBC)

The evidence presented by the Crown was not enough to suggest that Quinn voluntarily gave Forslund the beer bottle she was holding or had advance knowledge he would use it to assault the teenager, the ruling said.

"In other words, the only evidence that links Quinn to the beer bottle supports, at most, an inference that Quinn played a passive role in Forslund's acquisition of the bottle," Finch wrote.

"The evidence did not support the Crown's stated view of the evidence nor the inference that was necessary if the jury was to convict Quinn as an aider and that the Crown invited the jury to draw."

Finch said he was "not satisfied" that the verdict would have been the same had the trial judge corrected the misstated evidence by the Crown.

"In these circumstances, a miscarriage of justice may well have occurred," Finch wrote. "I would allow the appeal, set aside the conviction and order a new trial."

Devastating news

Sandra Martins-Toner says she has lost her faith in the justice system. (CBC)

Martins's parents said Friday that the Appeal Court decision has left them devastated.

Martins's mother, Sandra Martins-Toner, said that when a Crown prosecutor phoned her Friday morning to relay the outcome of Quinn's appeal, she "pretty much fell apart at that very moment."

"To have to sit through a trial, it's the most painful thing any person can go through," she told CBC News. "But to have to do it a second time, it's excruciating."

She said she is "completely disillusioned by the justice system."

"I just think that it's wrong … the victims will be put through this," said David Toner, Martins's stepfather.

"I understand that mistakes happen in law sometimes; occasionally, people are wrongly convicted of things that they didn't do.

"But in the Quinn case, we're not talking about circumstantial evidence. I don't see [on] what ground she legally has a right to an appeal and to continue torturing our family and wasting tax-payer money."