The video from Feb. 9 shows inmates viciously attacking convicted killer Kenny Green, 35, with homemade knives and pieces of a church pew.
The video was shown at the trial for Calvin Kenny, Jody Clarke and Justin Harvey, who are each charged with participating in a riot.
The court heard that on the day of the attack, an unusually high number of inmates filed into the chapel at Her Majesty's Penitentiary in St. John's before the Sunday service began.
Before the attack started, an inmate threw a towel over the lens of the surveillance camera.
Thirty seconds later, the towel drops to reveal a bloody mess, with a group of inmates piled on top of Green, stabbing and beating him, as correctional officers attempt to maintain control.
Clergy members can be seen hiding in the corner of the chapel.
Two other men – Philip Pynn and Justin Wiseman – were supposed to be tried with Kenny, Clarke and Harvey, but before the trial got underway, Wiseman pleaded guilty to taking part in the riot. He is to be sentenced on Friday.
The lawyer representing Pynn, who was convicted of manslaughter last week, asked that his client's case be heard separately from the other accused because he needed more time to prepare.
Pynn's trial has been scheduled to begin on Dec. 1.
Motive may have been retaliation
It is believed the attack on Green was in retaliation for the death of Joey Whalen a year earlier.
Green was awaiting trial on a second-degree murder charge in connection with Whalen's death when the riot happened. He was later convicted of manslaughter.
Despite being stabbed with shivs and beaten with pieces of church pew by other inmates, Green refused to give a statement to police.
Police had to obtain a court order to use the pictures of Green's injuries at trial.
At the time of the riot, 31 inmates were in the chapel, but none would talk to police.
The inmate who hit Green with the pew, Paul Connolly, pleaded guilty two weeks ago and was sentenced to two years in prison.