Lawyers for Toronto Police Const. James Forcillo began their bid to overturn his conviction on Monday by asking the Ontario Court of Appeal to reconsider a crucial interpretation of the way the fatal shooting of 18 year-old Sammy Yatim unfolded on a Toronto streetcar in 2013.

Last year, a jury acquitted Forcillo of second-degree murder but convicted him of attempted murder. He was sentenced to six years in prison but remains free on bail pending the outcome of his appeal.

Yatim's mother, Sahar Bahadi, attended the proceeding on Monday, telling reporters she believes the court will uphold Forcillo's conviction.

"Always, it's difficult. But I believe in justice," Bahadi said outside of court. "I believe he will go to jail."

According to a summary of the appeal filed in court, Forcillo's lawyers believe he is the only appellant "in the history of the commonwealth to be acquitted of having caused the death of someone but convicted of attempting to murder that same person during the course of the same transaction."

What opened the door for the jury to do so, Forcillo's lawyers say, was instructions from Justice Edward Then that allowed it to consider the officer's first three shots a separate event from his next six shots, even though they occurred just 5.5 seconds apart.

Sammy Yatim's mother, Sahar Bahadi, speaking outside of the Ontario Court of Appeal. She believes Forcillo's conviction will be upheld and he will go to prison. (Mike Heenan/CBC)

Forcillo's lawyer Michael Lacy spent much of Monday morning attempting to pick apart the logic behind this pivotal interpretation of the fatal shooting.

Lacy questioned how a conviction could be arrived at "from the same circumstances and the same factual event" as the acquittal.

"What came to be known as the two volleys of shots were so inextricably intertwined that they form part of a single, continuous transaction," Lacy argued.

The case is being heard by Chief Justice George Strathy, Justice David Doherty and Justice Gary Trotter.

Lacy told the three-judge panel that the separation of the two volleys of shots into "metaphysical increments" was "artificial" and lacks the "air of reality" required for it to have been put to the jury.

The first three shots did knock Yatim to the ground and one of the bullets paralyzed him.

"Isn't that a significant change in the landscape for the jury to consider? Chief Justice Strathy asked at one point.

Lacy disagreed, insisting that all of Forcillo's shots were part of "one factual transaction."

Forcillo's lawyers are also appealing the conviction on the grounds that they were unable to introduce evidence to suggest Yatim was attempting to commit what's known as suicide-by-cop, and therefore would not have responded to other, less lethal interventions from Forcillo.

This evidence included text messages and Google searches from Yatim's phone, as well as expert testimony.

Another lawyer for Forcillo, Joseph Wilkinson, argued Monday that the trial judge should have allowed the evidence to "counterbalance" the crown's position that Yatim was a "person in crisis" who Forcillo could have dealt with without lethal force.

The appeal will also challenge the mandatory minimum sentence handed down to Forcillo and lawyers will attempt to introduce new evidence they argue was not available during the trial.