One of three prison inmates on trial for the murder of another prisoner at a maximum security jail has admitted the killing and claims his co-accused were not involved.

Samoan born Tue Faave, 23, a member of the Bloods gang, was found strangled to death in a shower block at Auckland Prison at Paremoremo on March 1, 2009. He had also been stabbed.

Three other inmates, who identify themselves as belonging to the rival Crips gang, are on trial in the High Court at Auckland charged with his murder. All three have name suppression.

One of them today made the unexpected admission that he alone had killed Faave when the two had a fight over the serious assault of another Crips member. His lawyer, Simon Lance, said the killing amounted to manslaughter, not murder.

Mr Lance said his client, a 29-year-old, was angry and upset after the assault on a close friend, and that Faave had antagonized him.

"He was bragging to (the accused) about this assault - laughing about it. Not just saying Bs up (a pro-Bloods call) but 'hahahaha, what's happened to your bros, f*** you crabs', at a time of sadness, a time of grieving."

The accused went to Faave's cell block and covered the security cameras with toothpaste, getting his co-accused to help but not explaining what he was doing, Mr Lance said.

"There's no mistake he wanted to have a fight with Mr Faave, but he didn't want to kill him."

Punches were thrown but things turned more serious when Faave produced a sharp metal shank and tried to stab his opponent several times.

The accused reached for his own weapon, a "tea bong" - an improvised device made from an electrical cord used to heat water with electric currents - which he initially tried to use like a knuckle duster but ended up wrapping around Faave's neck.

"He held the cord around his neck, pulled and closed his eyes until Mr Faave stopped trying to stab him."

The other two defendants were not in the room when Faave was killed, but they were enlisted to help carry the body to the shower block.

For some inexplicable reason, the man returned to the body a short time later and stabbed him around the eyes and cheeks.

"When asked about this he finds it hard to say why - maybe it was out of anger or frustration," Mr Lance said.

"The crux of the matter is this: the death of Mr Faave was not what he intended or desired."

The accused came to New Zealand from Tonga when he was 13 years old and struggled at school, leaving at fifth form (Year 11).

Mr Lance asked the jury to make allowances for his lack of education and to take into account the prison environment in which the killing occurred.

The accused man started giving evidence today and told the jury that he had only wanted to give Faave a hiding.

"I don't think you should kill a person for what they say. For me, my intention was to smash Faave, not to kill Faave."

He will continue giving evidence on Monday.