Mangels has spent 17 years in jail for strangling his neighbour, Maureen McKinnel, in Arrowtown on Boxing Day in 1987.
The 38-year-old's naked body was found five days later dumped under the Arrow River bridge, but the case was only solved in 2003, when scientific developments meant the killer's DNA could be matched with that found under the woman's fingernails.
McKinnel's family said that they had "major con-cerns" about Mangels' release and were disappointed that the board had allowed him to live in Christchurch.
"We feel that Mr Mangels is still a risk to society and not ready for release," they said in a statement.
"We have serious concerns about his chance of reoffending and would not want another whanau to go through what we have."
The Parole Board, however, noted the rehabilitative work the murderer had done while locked up.
"As to the current position, Mr Mangels has done very well in the prison," board chairman Sir Ron Young said.
"It is no exaggeration to say his behaviour has been exemplary and he has had a strong work ethic, particularly so since 2016."
Mangels told the board he thought every day about why he had ended up behind bars. However, he maintained he was unable to recall anything of the violent incident.
A head injury he sustained after a run-in with a gang in 1999 meant he had no memories before the incident, he said.
"We are now satisfied that Mr Mangels is no longer an undue risk given the work he has done and given special conditions we propose," Sir Ron said.
Those conditions included:
• To live at an approved address in Christchurch.
•To submit to electronic monitoring and a 10pm-6am curfew.
• Not to go south of the Rakaia River.
• To attend any treatment as directed.
• Not to possess alcohol or non-prescription drugs.
• To attend a monitoring hearing in September.
• To inform Probation about any changes in employment
• Not to contact any victim of his offending.
