The board's most recent decision was provided to the Herald.
In it Parole Board chair Sir Ron Young said after the murder Mangels went on to commit a significant amount of "very serious offending" and had more than 80 convictions to his name.
However, his time in prison had seen a shift in his behaviour.
"He is a polite, compliant prisoner and no further rehabilitation is identified for him," said Sir Ron in the decision.
"It is said by the psychologist that he has demonstrated sustained appropriate behavioural change in the prison and is now at moderate risk of reoffending."
Before his 2019 hearing Mangels had completed all his rehabilitation including the Special Treatment Unit Programme and the Drug Treatment Programme.
There had been a possibility of him being released to work as part of the prison programme but McKinnel's family expressed concern about him doing that in their area.
At the time Mangels was serving his sentence at Otago Corrections Facility near Milton.
Mangels is now housed at Rolleston Prison just out of Christchurch.
He told the board he wanted to be released to a specific area of New Zealand where a friend of his was "working and would employ him".
"We think an extended period of reintegration of testing in more liberal circumstances is appropriate now for Mr Mangels," said Sir Ron.
"He has had a period in internal self care.
"He has had time working on prison farms and inside the prison, all of which so far have gone well.
"But given Mr Mangels' long history of violent offending and given the very violent murder he committed, we think a cautious approach to his reintegration is important."
Sir Ron said the fact that Mangels had also been in prison now for16 years also "emphasises the need for a cautious approach".
The board told the killer to participate in a period of release to work - and revealed he had been offered a job working in construction within the prison.
While Mangels had thus far refused the opportunity because he "did not want to work in construction", the board encouraged him to accept the offer.
"As to potential release, we have made it clear on previous occasions that we think it highly unlikely that Mr Mangels would be released by any board in the particular area or near the areas where a number of members of the family of the victim of his murder live," said Sir Ron.
"That is in an area from Dunedin south including Southland.
"The victims also expressed their concerns about release near the Christchurch area."
Sir Ron said the board currently had no view as to the appropriateness of a release to Christchurch.
