Two violent offenders charged with assaulting Dennis Oland in prison last year have changed their pleas to guilty.

Cody Alexander Muise, 27, and Aaron Marriott, 26, of Halifax, were scheduled to stand trial in Miramichi provincial court on Tuesday morning but instead entered the new pleas.

They admitted to punching and kicking Oland and knocking him to the ground in the visitor's area of Atlantic Institution, a maximum security prison in Renous, on July 31, 2016.

Oland, 49, suffered injuries to his face and was treated at the institution, said Crown prosecutor Melanie MacAulay.

MacAulay did not disclose the severity of Oland's injuries or suggest any possible motive but revealed details about the assault for the first time.

She said Oland had two visitors that day, and they were the last visitors in the room. As Oland was standing talking to them, Muise and Marriott approached and attacked, MacAulay said.

Muise, a convicted murderer, and Marriott, convicted of attempted murder, started taking swings at Oland and continued to punch and kick him while he was on the floor, she said.

Oland's visitors tried to break it up by standing between him and his attackers, but the assault continued until guards jumped in, MacAulay said.

Oland was serving a life sentence at the time after being found guilty of second-degree murder in the 2011 bludgeoning death of his father, Saint John multimillionaire Richard Oland.

He was later released on bail after the New Brunswick Court of Appeal overturned his conviction and ordered a new trial, citing an error in the trial judge's instructions to the jury.

Oland declines to comment

Oland was not present in court on Tuesday. Oland family lawyer Bill Teed offered no comment "at this time."

The Crown did not disclose the identity or gender of the two visitors who witnessed the assault.

MacAulay said she will be requesting victim impact statements before sentencing, scheduled for Nov. 23 at 1:30 p.m. in Miramichi via video feed from the Atlantic Institution.

Because the assault occurred at the maximum security prison, the Crown was proceeding by way of indictment, rather than the lesser summary offence of assault.

Indictable assault carries a maximum sentence of five years in prison.

More assault charges

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Aaron Marriott is serving a 15-year sentence for attempted murder after he admitted to shooting and injuring a man outside the IWK children's hospital in Halifax in 2008.

Muise and Marriott, who were both handcuffed and quiet throughout the court proceedings, agreed to the facts, as relayed by MacAulay.

Judge Natalie LeBlanc asked both men if they had anything to say, but both declined.

Both Muise and Marriott are facing additional, unrelated charges.

'We just want to make it abundantly clear that [Dennis Oland] has not been involved in any way, shape or form with respect to the laying of charges against these two individuals.' - Bill Teed, Oland family lawyer

The inmates are co-accused of assault causing bodily harm, and Marriott is charged with assault in another case.

They have not entered any pleas. They will appear in court at a later date on those charges.

Oland's family lawyer previously told CBC News Oland played no role in the assault charges being laid against Muise and Marriott.

"I just want to make it very clear on behalf of Dennis Oland that Dennis at no time has laid any complaint with respect to any alleged assault," Teed said in February.

Oland was not involved in any investigation or any discussion with the Crown prosecutor's office, Teed said at that time.

"There's been some inference drawn by some that he has, and we just want to make it abundantly clear that he has not been involved in any way, shape or form with respect to the laying of charges against these two individuals," he said.

Richard Oland

Richard Oland, 69, was found dead in his Saint John office on July 7, 2011. (Canadian Yachting Association)

The RCMP northeast district laid the charges against Muise and Marriott.

Muise is serving a life sentence for first-degree murder in a 2010 shooting death in Spryfield, N.S.

Marriott is serving a 15-year sentence for attempted murder in connection with a shooting outside the IWK children's hospital in Halifax in 2008.

Oland has been living in the Saint John area under court-imposed conditions for nearly a year, pending his retrial.

No date has been set yet, because of some unresolved issues, but the trial is expected to be held in 2018. A pre-trial conference is scheduled for Nov. 2 at 10 a.m.

Oland is accused of killing his 69-year-old father, whose body was discovered lying face down in a pool of blood in his Saint John investment firm office on July 7, 2011.

The businessman had suffered 45 blows to his head, neck and hands. His son was the last known person to see him alive, during a visit at his office the night before. No weapon was ever found.

With files from Tori Weldon