A teenage sex offender who doused a fellow inmate in scalding water told police he "wanted to burn and hurt the victim as much as possible".
Regan Philip Burrell, 19, was jailed for nearly four years in mid-2019 for sex offences against three young girls, one of whom he also blackmailed.
The defendant threatened to spread explicit photos of the victim if she did not meet him for sex, and after their liaison, he threatened to kill her dogs should she disclose what had happened between them.
One of the victims told the court at last year's sentencing that her life had been "completely destroyed" by her ordeal.
That sentencing judge on that occasion questioned whether Burrell had any remorse, a sentiment also expressed by Judge Kevin Phillips at the Dunedin District Court yesterday.
Shortly after the violent incident at the Otago Corrections Facility in August last year, he told police he was not finished with the victim.
Later, in an interview with Probation, he explained the victim was a "snitch".
Burrell retaliated, he said, "to save face".
He told the report writer he planned to punch the victim but was encouraged by other prisoners to commit a more serious assault.
The two men were in their wing awaiting their dinner at the time.
Burrell filled a one-litre container with boiling water and called out the victim's name, luring him to the cell opening through which meals are passed.
When the man came to the hatch, the defendant poured the water on him, connecting with his face and right arm.
Burrell then grabbed a cup of tea from another inmate and threw that at the man too.
He stated it was "only the start of things".
The victim was taken to Dunedin Hospital where he was diagnosed with second-degree burns to his elbow.
Counsel Anne Stevens QC said while her client was technically an adult, his conduct — affected by attention deficit hyperactivity disorder — showed great immaturity.
She described him as being like "a strutting little c**k in a prison".
"He doesn't think things through," Mrs Stevens said.
Since Burrell started seeing a psychologist, she told the court, there had been no further misbehaviour.
Judge Phillips called that the only "glimmer of light".
"This was vigilante action," he said.
While he had to impose a further prison term on top of what Burrell was currently serving, he said he was mindful of not imposing a crushing sentence.
He jailed the teenager for another two and a-half years on a charge of injuring with intent to do grievous bodily harm.
Burrell's first parole hearing, which had been set down for October, would now take place next year.