A trial judge relied on a police officer's "bias" and "partiality" when he convicted a Pembroke dentist of impaired driving in a 2011 crash that killed a father of three, a defence lawyer argued at Ontario's highest court Tuesday. 

The case of Christy Natsis reached the Ontario Court of Appeal Tuesday as the prominent dentist's lawyers tried to have her acquitted of impaired and dangerous driving causing death or a have new trial ordered.

She was found guilty in the death of Bryan Casey, 50, who left behind a wife and three kids in the March 31, 2011 crash near Arnprior, Ont.

During a 55-day trial in Ottawa that stretched over three years, court heard that Natsis' SUV crossed the centre line of Highway 17 and struck Casey's pickup truck. 

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Bryan Casey, 50, was a husband and father of three.

Ontario Court Justice Neil Kozloff sentenced her in November 2015 to five years in prison, plus an additional 40 days for breaching her bail conditions by purchasing two bottles of vodka in the months following the crash.

Natsis is currently out on bail since filing her appeal.

Officer 'can't be relied on'

Arguing her case before a panel of three judges is high-profile lawyer Marie Henein — who successfully defended former CBC broadcaster Jian Ghomeshi at his sexual assault trial — and her associate, Matthew Gourlay. 

The pair picked apart the investigation that led to Natsis' May 2015 conviction, zeroing in on what they said were errors Justice Kozloff made regarding the reliability and admissibility of the two officers who testified at the trial. 

Henein argued that Ontario Provincial Police Const. Shawn Kelly, the lead collision investigator in the case, ventured outside of his expertise and accused him of burying evidence, including testimony from a witness who said Natsis's vehicle wasn't weaving on the highway. 

"That's a problem when the court has to put faith and trust in him to look at everything objectively," Henein said Tuesday.

"Kelly can't be relied on."

Bryan Casey widow and father

Bryan Casey's widow, left, and father leave the Ontario Court of Appeal building on Tuesday, Nov. 14, 2017. A woman found guilty in Casey's death has launched an appeal. (Laurie Fagan/CBC)

Natsis's blood-alcohol level was nearly 2½ times the legal limit but Kozloff tossed that evidence after ruling the arresting officer denied her the right to speak with her lawyer. Casey's blood-alcohol limit was twice the legal limit, court heard. 

Gourlay added to Henein's arguments Tuesday, saying evidence presented by two other OPP officers, who peer reviewed Kelly's report on the investigation, should be tossed out and that they failed to catch Kelly's mistakes.

Henein and Gourlay said Tuesday the judge erred in allowing any of Kelly's evidence to stand. 

Evidence spoke for itself: Crown

The Crown came to the defence of the lead investigator, saying there was no proof Kelly had an agenda when probing the fatal crash and his alleged bias wasn't serious enough to warrant a complete exclusion of his evidence at the trial.  

According to Crown counsel Jamie Klukach, the evidence spoke for itself. 

"Kelly didn't arrive on the scene and create gouges and scrapes in the road and he didn't fabricate data from vehicle control modules," Klukach said. 

"Kelly didn't fudge or fabricate his field notes."

Ontario Court of Appeal

The Court of Appeal for Ontario is expected to hear the case in a one-day hearing on Tuesday, Nov. 14, 2017. (Laurie Fagan/CBC)

While the trial judge did throw out parts of the investigator's evidence that he ruled was out of his area of expertise, he did accept his testimony on road measurements, the debris field, and the photo evidence of how the collision unfolded. 

"The trial judge was able to see for himself what Kelly observed and the area of impact is non-controvertible," Klukach added. 

Casey's widow, LeeEllen Carroll, and his father, William Casey, both attended the appeal hearing in Toronto on Tuesday. Natsis did not attend the hearing, but her husband Bruce Harle was in the courtroom. 

The panel of judges reserved their decision on whether or not to order a new trial for a later date that has yet to be determined.

With files from Laurie Fagan