Duke Allan Wayne Schafer had served just under six months of a sentence for drug offences when Carl William Sedgwick Bloomfield strangled him in May last year.

Bloomfield pleaded guilty to murder for the attack that took less than three minutes, and was sentenced to life in prison on Friday.

At the time the 26-year-old was serving a sentence for a violent robbery and was "capable of sadistic acts", Justice Martin Burns said.

Among his previous victims was a teenager whose ear he sliced before taking photos of his "handiwork".

Bloomfield had been stewing on a comment made by Schafer when he decided to kill him at the Woodford Correctional Centre, the court was told.

"As far as I can tell, you barely knew him, but he said something the previous day, most probably in jest, to which you took exception," Justice Burns said.

"He tried to break free but you're a much bigger man than him."

Bloomfield used a razor to fashion the weapon out of bed linen, the court was told.

Schafer's family were present to hear the sentence and shared the impact of his murder through a statement read to the court.

"The death has taken a great toll on my family. My elderly mother, Duke's grandmother, has had nightmares ever since, waking up screaming," the statement from the victim's father said.

"My wife spent weeks crying and trying to come to terms with this senseless act ... to this day she still has issues with the idea that she will never see or talk to her son again."

Schafer's father said the last conversation he had with his son were "angry words" and he would never have the chance to make sure he knew how much he cared.

The death was totally preventable and he would never understand how it could have been allowed to happen in jail, he said.

Given the murder and Bloomfield's past, Justice Burns said the parole board "will need to think long and hard" before it ever considered his release.

Australian Associated Press