A troubled Nova Scotia teenager who's already been convicted of murder and participating in a riot at a youth jail has now pleaded guilty to assaulting a guard at an adult facility.

The 19-year-old was in provincial court in Pictou this week to answer to charges of assault and assaulting a peace officer. He pleaded guilty to assaulting a peace officer. The other charge will be dealt with when he is sentenced Feb. 20.

The charges stem from an incident at the Northeast Nova Scotia Correctional Centre in New Glasgow. The teen, whose identity is protected by a publication ban, was transferred to the jail in Pictou County after participating in a riot at the Waterville youth jail in September 2016.

Daniel Pellerin

Daniel Michael Pellerin died in August 2014 after being stabbed in Dartmouth. (Facebook)

At the time of the riot, the teenager was serving a four-year jail term after pleading guilty to second-degree murder in the August 2014 death of Daniel Pellerin, 28, who was stabbed in Dartmouth and later died in hospital.

The four years in youth jail were part of an intensive, rehabilitative custody and supervision sentence, which was to include three years of supervision in the community after the jail term. But the riot derailed the specialized sentence.

During about a year in the adult jail in Pictou, the teen was kept in virtual isolation, a fact that provoked outcry from a prisoners' rights advocate and the original sentencing judge.

Staff at the Waterville youth jail expressed fears about having the teen transferred back into their custody because of his violent and unpredictable nature. Despite their objections, he was sent back to Waterville this fall.

At the time of his sentencing for murder in June 2015, Judge Anne Derrick said the supervision and custody order would "not be a walk in the park."

"It will be challenging, demanding, and difficult," Derrick said. "It has the potential of liberating you from the damage done by your experiences and the enormous burdens you are carrying of trauma and anger."

Northeast Nova Scotia Correctional Facility

The Northeast Nova Scotia Correctional Facility in New Glasgow. (CBC)

But at his sentence review last September, the court heard he has struggled to stay on course. Since his return to Waterville, he has been charged with assaulting another inmate.

He has not always followed the training and counselling programs that were put in place for him.

But in September, he promised to try again. "I'm good to work with those people," he said, indicating health-care workers and jail staff gathered in the courtroom. "I don't want to dwell on the past too much. I just want to move forward."

Another man, Trevor Kyle Hannan, is still facing a charge of first-degree murder in Pellerin's death. Hannan was supposed to go to trial last summer, but he parted company with his lawyer, forcing a postponement. The trial may not happen until 2019.

Pictou prison

A photo from inside the Northeast Nova Scotia Correctional Facility. (CBC)