TORONTO - Ontario's top court has ordered a new first-degree murder trial for a woman accusing Terri-Lynne McClintic of beating her up in prison.

Aimee McIntyre was found guilty in May 2010 of first-degree murder in the death of her ex-boyfriend.

Her trial heard that she drove two men to her ex's apartment, one of them stabbed him six times, then McIntyre drove the pair away from the scene, helped them dispose of the knife and helped wash their clothes.

McClintic, who is serving a life sentence for the first-degree murder of eight-year-old Tori Stafford, is charged with assault causing bodily harm stemming from an incident in prison in Kitchener, Ont.

McIntyre is also serving a life sentence, but in a decision released today the Court of Appeal for Ontario set aside her first-degree murder conviction and ordered a new trial.

The court found that the judge at her trial made several errors in law that mean McIntyre did not receive a fair trial.