Cory McCaughan was originally found guilty of dangerous driving causing death and given a two-year conditional sentence for the July 2004 incident near Anola, about 30 kilometres east of Winnipeg.
Christine Bruinson Dourma, 38, suffered massive head trauma after hopping onto the side of the moving rig, apparently in an attempt to get McCaughan to continue talking with her.
The Court of Appeal ruled Thursday that McCaughan was wrongly convicted by a judge who erroneously found his driving to be a "marked departure from the normal standard of care." The court overturned his conviction and replaced it with an acquittal, rather than ordering a new trial.
McCaughan had told police he saw Dourma dangling from the side of the truck but kept driving until she disappeared from sight and fell under his wheels. He believed she had already returned to her own vehicle. Witnesses told court an enraged McCaughan left his rig and began screaming at the body of Dourma.
The victim's father, Charles Bruinson, said McCaughan called his nearby home moments later. McCaughan spoke with Dourma's 10-year-old daughter, telling her he'd just "run over your mom." Bruinson and the girl rushed to find Dourma dead on the ground.
The family had gathered that evening to celebrate Bruinson's birthday. The party turned sour when McCaughan and Dourma began arguing. McCaughan wanted Dourma to accompany him the next day while driving in his truck because he had to work. Dourma didn't want to go, choosing instead to go to the beach, according to her father. McCaughan stormed out of the home, and Dourma followed.
Queen's Bench Justice Daniel Kennedy ruled at trial last year that McCaughan had been reckless in failing to notice Dourma. He acquitted McCaughan of the more serious charge of criminal negligence causing death, saying he believed the case involved a "momentary lapse" of judgment.
Both the Crown and defence filed appeals of Kennedy's decision.
The Crown argued he should have been convicted of the more serious negligence charge and that his sentence was too lenient. The Crown sought up to four years in custody for McCaughan, citing the facts of the killing and his violent criminal past.
Prosecutor Ami Kotler called evidence of a similar incident involving McCaughan and his second wife several months before Dourma died. The woman told court he tried to run her down with his semi-trailer following an argument. McCaughan was originally charged with assault, but the case was dropped once he agreed to have no contact with her.
McCaughan's first marriage had also ended badly, court was told. He was embroiled in a property dispute with the woman and torched the family home. He was later convicted of arson.
Defence lawyer Mark Wasyliw argued that Dourma's death was a tragic accident, not a criminal offence.
"The accused believed that the deceased had returned to her vehicle and that there was no longer any risk to the deceased if he exited the lot. The trial judge ought to have accepted that belief because he found that it was not dangerous for the accused to have driven forward to leave the parking lot," Appeal Court Justice Alan MacInnes wrote in Thursday's decision.
"Had the trial judge considered the accused's state of mind he could not, in my view, have found the momentary lapse constituted a marked departure from the norm."