Flanked by half a dozen prison guards and two police officers, the prisoner accused of killing prison officer Jason Palmer stood quietly but defiantly in the dock.

Latu Savelio Halangingie Kepu, whose name suppression was lifted yesterday, had restraints on his hands as he was led into the Hamilton District Court by a procession of prison guards.

Originally charged with assaulting Mr Palmer after he allegedly punched him to the ground on May 15, the 21-year-old was yesterday charged with his manslaughter.

Mr Palmer, a 32-year-old father-of-two, later died in Middlemore Hospital with irreversible brain damage.

He was the first prison officer in New Zealand to be killed while on duty.

Kepu, who has alleged Killer Beez gang links, entered no plea and has been remanded in custody before he is to reappear in Hamilton District Court on July 13.

Mr Palmer's mother, Ada Palmer, earlier said from her United States home she hoped to one day meet the man who killed her son.

"I want to ask him why," she said.

"What was so bad that you had to kill my son? To kill someone there has to be some sort of strong emotion ... I want to know what it was and I think he needs to tell me."

Mrs Palmer said she did not hate Kepu but added: "Am I angry at him? Massively."

Meanwhile, the Corrections Association of New Zealand is calling for an independent inquiry into Mr Palmer's death. Canz president Beven Hanlon said an independent investigation would answer guards' questions about the death of a colleague at the hands of a known violent prisoner.

Mr Hanlon said an increasing number of guards had been assaulted at prisons and staff deserved to be safe at work.

"This will only be achieved by an independent investigation into this incident giving us an unbiased determination of what lead up to and contributed to the death of corrections officer Palmer," he said.

The Minister of Corrections, Judith Collins, agreed with Mr Hanlon that it was important to find out exactly what happened on May 15.

But she has ruled out an independent inquiry, saying the full facts should emerge from investigations by the Department of Corrections, police, the Office of the Ombudsman and the Department of Labour.

Mr Hanlon said if there was nothing to hide, there should be no problem conducting an independent inquiry.

"Too many corrections officers are being assaulted every day and it has become an expectation.

"We will never learn from this tragedy if we don't shine a light on the decisions, policies and inactions that contributed to this death."

Last month Prime Minister John Key said the Corrections facility at Spring Hill was operating appropriately, despite the death of Mr Palmer.

Mr Key said it was the first time that a prison officer had been killed on the job in New Zealand and that indicated there was not a systematic problem.