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The 42-year-old appeared before the New Zealand Parole Board at a hearing held at an undisclosed location last month.
He was just 15 when he strangled Miss McKinnel (38) at her parents' Arrowtown holiday home on Boxing Day 1987, and threw her body off the Arrow River bridge. Her body was discovered four days later.
Mangles claims he had no memory of the murder. The board noted this might be because he was consuming drugs/alcohol at the time, and he had also received a serious head injury around 1998.
Between the murder and his conviction 16 years later, he accumulated 80 convictions and 27 prison terms.
Police investigated about 500 people in connection with the murder, including Mangles.
He was arrested in Nelson on a disorderly behaviour charge in January 2003 and agreed to provide a voluntary blood sample.
That DNA testing proved he was four billion times more likely than any other person to be the one who left material under Miss McKinnel's fingernails.
He was sentenced for her murder on April 6, 2004 and first became eligible for parole from March 24, 2013, which was declined.
The board noted he appeared despondent about ''the way forward''.
A recent policy change prompted by a high-profile escape of another inmate meant his work outside the wire on a prison farm had ceased.
''It is clear that he was gaining a lot from that work,'' the board noted.
Before his hearing, the board received written submissions from representatives of Miss McKinnel, who said he remained a risk to the community.
The board noted Mangles had completed several rehabilitation programmes, as alcohol and drugs were identified as a risk factor for him.
Personal issues from his time in state care as a young person could be addressed by counselling, and he required extensive work on a reintegration plan.
Mangles remained an undue risk to the community and had not completed any intensive work to reduce his risk of violent offending, the board said.