Mark Quentin Waitere (40) appeared in the Dunedin District Court last week on a charge of injuring with intent to injure and five assaults.
The defendant had been locked up at the Otago Corrections Facility after continued violence against his wife and her family.
But before he could be sentenced, Waitere added to his rap sheet.
On September 23, during a two-hour recreational period in the prison's yard, the defendant was with a Christchurch man charged with murder.
They began a ``friendly sparring session'' but minutes later one of Waitere's associates approached the victim from behind and punched him in the side of the head.
The assailant, who will appear in court this week, then stomped on the man as he lay on the ground.
Two others joined the action and delivered their own blows before Waitere too kicked the victim.
Further assaults took place before the man was allowed to get to his feet and stagger away.
However, 30 seconds later Waitere punched him again and the others joined in.
Another man, who had previously been uninvolved, dropped his knees on to the victim's head ``forcefully'' up to three times.
As the alleged murderer got to his feet again, Waitere kicked him once more in the side.
The flashpoint was captured on CCTV and the victim was later found unresponsive in his cell.
He displayed ``seizure-like activity for 20-30 seconds'' and had a large lump on his head, police said.
Despite sustaining the barrage of blows, the victim aimed his criticisms at Corrections and police for not ensuring his safety, rather than the inmates responsible, the court heard.
Counsel Andrew Dawson said the man appeared to have ``welcomed the assault'' as it allowed him to make a point about his remand status.
Judge Kevin Phillips detailed Waitere's wide-ranging history of violence and the incidents that resulted in him losing bail.
On May 21, he was drinking at a party in Palmerston.
When his wife arrived, he opened the car door and immediately started punching her in the head, then pursued her as she tried to escape, fighting those who tried to thwart him.
Waitere was arrested and taken to the Dunedin station.
While hitch-hiking north on his release, his partner and her mother stopped to pick him up, but time in the cells had not cooled his temper.
The defendant abused his wife and then punched her multiple times in the head and body while her mother drove them back to the police station.
The victim now said the relationship had been repaired but she believed it would be best for Waitere to move to the North Island.
A letter to the court showed a ``high degree of ability'', Judge Phillips said, but the defendant was classified as being at a high risk of reoffending because he continued to attempt to justify his actions.
Waitere was jailed for two years, 11 months.
