Closing arguments have begun in the trial of a man accused in the death of 17-year-old Brett Bourne. Bourne was fatally stabbed at Kelvin High School in 2015.

The accused, who was 17 at the time, can't be named because of the Youth Criminal Justice Act.

Tuesday, defense lawyer Greg Brodsky told the jury "it was a split second decision," and said "it's not an issue of whether he made a correct decision, but a reasonable decision."

Earlier, court heard Bourne tried to start a fight with a student at the school, but the other teen didn't want to fight.

Bourne chased that student inside the school, and he in turn was followed into the school by that student's friends, including the accused.

The accused testified "I thought Brett had a knife. After I saw Brett reach into his pocket, I stabbed Brett."

Tuesday, Brodsky argued the accused "did what was necessary to protect his friend," and said the victim was "a determined irrational fellow, talking to him would have been a waste of time."

But in her closing remarks to the jury, Crown attorney Erika Dolcetti said “Brett may have deserved a criminal charge of assault, but he didn’t deserve to die.” 

She pointed out statements the accused made to police and his mother that were later revealed to be untrue. She told jurors, “We say it’s clear the accused is prepared to lie. He lied again and again. He is untrustworthy, discount the accused’s version of events.” 

Dolcetti told the jury that she did not believe it was reasonable for the accused to stab Bourne because of what she described as “a school yard fight.”  She told the jury, “He did not need to bring a knife to a fist fight.”

She concluded “be comfortable coming to the only common sense conclusion possible. The accused is guilty of second degree murder.”

The judge is expected to read her charge to the jury on Thursday, then it will be up to the jurors to decide the accused’s fate.