TORONTO -- WARNING: This story contains graphic details that might be disturbing to some readers

A teenaged boy helped other teens immobilize a fellow student as the victim was sexually assaulted with a broom handle at a prestigious Toronto high school in November 2018, court heard Wednesday.

The accused, a former student of the all-boys St. Michael's College School, pleaded not guilty to two counts each of gang sexual assault, sexual assault with a weapon, and assault with a weapon. The alleged incidents -- two sex assaults and an assault -- occurred on campus in the fall of 2018.

Det. Const. Daniel Sunghing with the Toronto police sex crimes unit, the lead investigator on the case, walked court through a cellphone video taken on Nov. 7, 2018, that shows a boy being sexually assaulted as others cheered and laughed.

Screams are also heard in the video, which was taken in the locker room of one of the school's football teams and lasts 22 seconds. The video was widely shared on cocial media, court heard.

It shows the victim trying to block the broom handle with his hands, which are then grabbed and held back by one of the boys surrounding him.

Sunghing said the boy holding the victim's hands is the accused.

"You can see that the facial features match that of (the accused)," Sunghing said.

The detective also identified the accused in surveillance videos outside the locker room that he says show the accused walking into the locker room with the complainant at 6:32 p.m. The clothing and shoes in the surveillance video matched that of the accused in the cellphone video, Sunghing said.

Surveillance video also shows the accused teen leaving the locker room at 6:43 p.m. and the victim leaving a minute later, court heard.

"As (the victim) exits the locker room, he appears to check himself, adjust his pants before going up the stairs," Sunghing said.

The accused teen's lawyer, Geary Tomlinson, has not conceded that the boy in the video is his client. None of the boys involved can be named under provisions of the Youth Criminal Justice Act.

The teen on trial is also accused of sexually assaulting another student in a similar fashion on Oct. 17, 2018, but little evidence of that incident was presented on Wednesday.

Tomlinson told court about an alibi for his client that day. He said his client's transit card was used at 5:30 p.m. at Union Station in downtown Toronto -- about the same time the alleged sexual assault occurred.

St. Michael's College School,

"If this was (the accused's) card and if he did use this card, it would be next to impossible to be in two places at once," Tomlinson said to Sunghing.

"Next to impossible, yes," Sunghing said.

The detective said police only became aware of the accused's possible alibi in late January, and that no surveillance videos had been retained by transit authorities that could corroborate it.

Four teens have already pleaded guilty in the St. Michael's case, which sparked a national conversation about bullying and had a profound effect on the school's community.

In October, three teens pleaded guilty to sexual assault with a weapon and assault with a weapon for their roles. They were sentenced to two years of probation.

One of them also pleaded guilty to making child pornography for recording one of the sex assaults -- the Nov. 7 incident -- in a video that was then shared widely.

Charges against two other students were dropped, while another received a two-year probationary sentence with no jail time after pleading guilty last summer.

Police began investigating in mid-November 2018, after media inquired about the cellphone video, Sunghing said Wednesday.

He said he visited the school, spoke to the principal and examined the locker room. He interviewed the first complainant the next day.

Wednesday morning's proceedings were plagued by technical issues showing the videos, which stalled several dozen times and prompted an early recess.

The trial continues April 1.

This report by The Canadian Press was first published March 4, 2020.