A prisoner who attacked a man accused of a Christchurch murder has had more than two years added to his jail sentence.
Bronson Honetana Toki (28) was serving time at Otago Corrections Facility on dishonesty charges on September 23.
He and fellow inmates were spending their two-hour recreation period in the exercise yard, the Dunedin District Court heard this week.
Mark Quentin Waitere (40) was engaged in a ''friendly sparring session'' with the victim when Toki intervened.
CCTV showed him approach the victim from behind and punch him in the right side of the head.
When the prisoner, who is currently awaiting trial, fell to the ground Toki, continued the brutal assault.
He stomped on the man about nine times, Judge Kevin Phillips said.
Others joined in.
Waitere was jailed for two years 11 months for his role in the pack attack, along with other violence charges pre-dating it.
Trent Willis (21) was handed a term of five years four months but that included a range of other offences.
Two other men allegedly involved have denied the charges against them.
Toki, too, was heading for trial when he eventually pleaded guilty to injuring with intent to injure.
With footage from the prison clearly showing Toki's role as the primary offender, Judge Phillips questioned why it had taken so long for him to plead guilty.
The victim struggled to his feet after the first wave of blows, but it was not the end of the violence.
He was making his way towards the yard's exit when Toki and others laid into him again.
The man was later found in his cell unresponsive and suffered seizures because of his head injuries.
Judge Phillips outlined the seriousness of the incident.
''You're inmates in prison, you're attacking a defenceless inmate ... you kicked him to his head, you attacked him as a group. There was, in my view, extreme violence,'' he said.
''No warning, no provocation whatsoever.''
The judge said Toki had a ''very violent footprint'', with reference to his previous convictions.
The defendant further weakened his position through an interview before sentencing in which he minimised his offending.
He attempted to ''shift the blame'' on to the victim when discussing the episode, the court heard.
Defence counsel Jim Takas said his client was far from a lost cause.
Toki had engaged in counselling at the prison and had tried to organise a spot in a residential rehabilitation programme.
''He's an intelligent man not acting very intelligently over the years,'' Mr Takas said.
