A former police officer whose investigative work helped convict a man for killing his former girlfriend says her family will feel "gutted" by his release.
Mark Pakenham was released on parole yesterday after serving half of his six-year seven-month sentence.
He was convicted of manslaughter in 2013 after admitting he killed Sara Niethe in Kaihere Domain in Waikato in 2003, by injecting the 31-year-old with methamphetamine.
Glenn Tinsley, who investigated the case for 10 years, said it would be a hard day for Ms Niethe's family.
"We can all put ourselves in that family's position, and how would you feel - you know, you'd be gutted.
"But the reality is that it's inevitable that one day he would be released. For them, if he were made to spend more time on it [in prison], that might have eased their loss somewhat. They would have been preparing themselves but it won't make it any easier."
Ms Niethe's body was never found, and Mr Tinsley said he thought Pakenham knew where it was and was not telling anyone.
"It's one of my biggest desires to assist the family to recover the remains of their mother, daughter, sister," he said.
"I do believe that, regardless of what he says to the Parole Board, it is within his means to be able to assist there, and I would appeal to him to do the right thing ... It's well within his control to do something about that and I'd urge him to do so."
Pakenham is subject to special conditions until the formal end of his sentence in March 2018.