The former partner of slain Mangakino police officer Constable Murray Stretch is "flabbergasted" his killer hasn't been released from prison.

Claire Horton, from Tauranga, said Carlos Namana, who brutally beat and kicked her then partner to death had done his time and she hoped he wasn't being kept in jail longer just because he had killed a police officer.

"Would he have been given parole had Murray not been a policeman? If that's the case, that's not okay. No one deserves to die whether they are a butcher or a policeman."

Namana is serving a life sentence with a minimum non-parole period of 16 years for the brutal murder of Stretch 19 years ago.

Stretch, a 38-year-old father of two sons, was investigating a burglary in May 1999 when he was beaten and kicked to death by then 19-year-old Namana.

Namana was sentenced on October 20, 1999, and became eligible to be released on parole on 28 May, 2015.

A New Zealand Parole Board decision, released to the media yesterday, said Namana had used his time in prison well, particularly lately.

However, it was deemed that there was still too much risk he could reoffend and the board had recommended he do more programmes during the coming year before applying for parole again.

Horton said she would "most probably" never forgive Namana but she didn't think he should still be behind bars. "He has done his time."

She said it was 19 years ago, Namana was 19 at the time and he had worked hard while in prison to change.

About six years ago, Horton met Namana face to face as part of a restorative justice process.

"I was pleased I did it. It was definitely helpful. I wanted to see that he made some changes and I think for Carlos, he has been trying to really hard."

"Being angry and bitter the rest of your life doesn't change anything."

Horton said she expected Namana to get parole three years ago.

Namana, now 38, has held a minimum security classification since July 2014 and had been misconduct-free since the beginning of 2012, the parole board decision said.

He completed a drug treatment programme in 2015 and went on to attend the Special Treatment Unit Rehabilitation Programme.

During the years he has achieved a number of unit standards in subjects as varied as introductory furniture making, carpentry, horticulture, engineering and laundry work, the decision said.

He is currently working with the Puppies in Prison programme and is housed in the inner self-care unit.

While there, he has participated in 14 escorted outings outside the prison, mainly to do shopping for the unit.

He participated in a whānau hui in August last year and has had regular visits from his support people. These include five members of his Circle of Support and Accountability group, the majority of whom were members of a church.

During his parole hearing, his lawyer emphasised Namana's increased maturity and self-awareness, which had seen him grow from an "angry violent youth to a skilled, reflective adult".

Namana is fortunate to have loyal support from his support group who had offered him not only employment and accommodation post-release, but also a commitment to support him in tertiary studies and other issues he might face, the decision said.

However, the decision said "while all of this was certainly impressive", Namana's history showed he struggled from time to time, in particular when dealing with his emotions, and was assessed high risk of violent reoffending and moderate risk of general offending.

It also said he had had limited exposure to the community and the parole board was not satisfied it had reached the point where he could be safely released.

"We agree with the writer of the latest psychological report that his risk of reoffending is likely to be mitigated by engaging in a stepwise gradual reintegration pathway. He needs to be able to demonstrate that he can apply the skills learnt in the various programmes he has undertaken, outside the prison setting and in a variety of situations," the decision said.

Namana will apply again before the end of May 2019.

Meanwhile, this Saturday marks 19 years since Stretch was killed.

Horton said every year on the anniversary she made the trip back to Mangakino to put flowers on Stretch's grave and she would do the same this weekend with other members of Stretch's family.