SYDNEY, N.S. -- A 15-year-old Cape Breton youth was not acting differently than a typical boy his age when, in the middle of ordinary horseplay, he pushed a fellow high school student under the wheels of a moving school bus, one of the boy's lawyers told court Wednesday.

Defence lawyer James Snow made the remark in his closing submission at the boy's trial for criminal negligence causing the death of 18-year-old Christopher Walter Chafe, who died on the afternoon of Jan. 11, 2015.

Snow said Chafe's grisly death was the result of "momentary inadvertence," not reckless behaviour. He told the judge-only trial in youth court in Sydney that there was rowdy "goofing around" among students outside Sydney Academy that day, but he said there was no evidence of fighting or aggression.

The defence lawyer noted that some witnesses testified that the fatal push wasn't a firm shove, but rather a "go on, get out of here push."

The accused, whose identity if protected under the Youth Criminal Justice Act, should not be convicted of the crime because his actions were within the norm for a boy his age, Snow said.

"This has to come into play here," Snow said. "We'd have a different case altogether if we were dealing with a 30-year-old."

Snow also argued that it was reasonable to conclude the accused did not see the bus until it was too late, based on the fact that neither boy was facing the approaching vehicle.

Crown prosecutor Mark Gouthro argued that evidence from the majority of the witnesses showed both they and the accused knew the yellow, 11-metre bus was coming at a relatively slow speed.

Gouthro told the court the accused was also aware of the danger because he had pushed Chafe over a snowbank and into the slush-covered street once before the bus arrived.

More than one witness testified the Chafe had joked with the accused over what would happen if he was pushed in front of the bus. Another witness said he heard the accused say he would do it, and then asked Chafe if he was ready.

As for the push itself, Gouthro drew the court's attention to witnesses -- most of them students standing nearby -- who testified that the accused used two hands to shove Chafe in the chest.

There was conflicting testimony on how fast the bus was going.

Chafe suffered fatal head wounds and was pronounced dead at the scene at 2:31 p.m.

Gouthro said the accused was aware of the danger, but "went ahead and did it anyway."

The prosecutor said the actions of the accused showed a wanton disregard for the safety of others and a marked departure from what a reasonably prudent person would do in similar circumstances.

"The accused should have known that Chris Chafe was going to fall ... and that a bus was approaching," he told the court.

Provincial court Judge Peter Ross said the case law dealing with criminal negligence causing death left him uncertain as to how the age of the accused should factor into his decision. He asked the Crown and defence lawyers to search for more case law on the subject.

"It's a difficult area," said Ross. "It's especially so when we have a 15-year-old charged with this offence."

Ross said he plans to deliver his decision Oct. 7.