Javed Mills' family was fooled for more than three years that their son was alive.

The mother of slain Auckland man Javed Mills has voiced concerns about the decision to release her son's killer on parole, fearing he is a danger to the community.

James Cooper, now 30, had been denied parole in 2017 and 2016 but was released this month on conditions including that he submit to electronic monitoring and not contact Mills' family.

He was serving a sentence of seven years and three months for manslaughter and perverting the course of justice after being found not guilty of Mills' murder at his trial in 2013.

STUFF James Cooper pictured during his 2013 trial.

Javed's mother, Lichelle Mills said the parole board's decision was very disappointing for her and her family.

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"I wouldn't be surprised at all if he (Cooper) re-offended down the track, it's not will he re-offend, it's when will he be caught again," Mills said.

Javed's death was a mystery until a headless skeleton was found in a Mt Wellington garage in September 2011.

At a parole hearing in October 2015, Mills pleaded in a letter to the parole board not to release Cooper.

She wrote in her submission that Cooper needed psychological help.

"He is a pathological liar ... he has not spoken a word of truth or admitted what he had done, that would be the first step he would take if he was remorseful for what he has done," she said.

"He really needs to be given help. This guy is really crazy."

Mills said the parole process had been very difficult and she had stopped going to parole hearings because she refused to keep on reliving what Cooper had done.

"It was just harrowing."

During his trial Cooper told police he struck Mills in the head after he "lost his marbles" during an argument in an oversized doll house called "the den" - a place where the pair would smoke cannabis and listen to heavy metal music.

When he realised Mills was dead, Cooper wrapped the body in a blanket and placed him underneath "the den" where he left him for two days.

When the body started to smell as it decomposed, Cooper then dug a grave half a metre deep and "chucked him in there" where he remained for 12 months.

While exhuming the remains to remove them, the head of the skeleton fell off backwards. Cooper then used a mallet to crush the skull before scattering the fragments onto the neighbouring property.

The rest of the bones were then put in a red-topped recycling bin where they remained behind the den before Cooper wheeled the bin off to a garage set to be demolished.

Cooper tormented the Mills family after killing Javed, setting up a fake social media account and communicating with the family. He also withdrew Mills' weekly Work and Income benefit and used his eftpos card regularly.

Cooper's mind games "rubbed salt into the wound", she said.

"I think that was just part of his game and to be upset and to be dragged into that game in that way showed he has one very sick mind," Mills said.

Mills declined to elaborate on the other ways Cooper psychologically tormented her family, fearing it might agitate him to strike out at her other sons.

"My youngest son has a little chap now, he's almost eight months old so we don't want to bring anything unnecessarily onto the family.

"I don't think that it's probably the time now to worry about that anymore because he's out isn't he, and anything now would be deemed to be kind of spiteful I imagine," she said.

Cooper will be subject to tightly controlled residential restrictions for at least the first three months of his release - the restrictions will remain until he returns to the parole board for a face-to-face hearing in September.