More than three decades after his release from his wrongful imprisonment, Arthur Allan Thomas is still trying to black out the memories of what happened to him.

Now in his 70s and with the gentle demeanour of a favourite grandparent, his eyes fill with tears when he is asked if his false conviction and years in jail haunt him.

"I do try and forget, because if I keep thinking about those terrible times, my life becomes unbearable," he said.

"I try to push away these negative things in my mind about what these bastards did to me so I can lead a reasonable life."

Mr Thomas - twice convicted of murdering Jeannette and Harvey Crewe but pardoned in 1979 - was angry that a plea from the couple's only child, Rochelle, to the Police Commissioner for the case to be reinvestigated had been unsuccessful.

The case will instead be reviewed by senior investigator Detective Superintendent Andy Lovelock - who will not be looking for new suspects.

"I'm expecting it to be another cover-up, I'm sad to say," said Mr Thomas.

"I used to have a lot of faith in the police but it was unbelievable what they did ... An innocent man went to prison and a little girl lost her parents and never knew why.

"We have police inquiring of police. But it has to be independent. We need an overseas investigator to look at the case, otherwise it will be a complete waste of taxpayers' money."

Mr Thomas and Ms Crewe have never met but he said he was willing to back her up if she wanted to petition Prime Minister John Key on the matter.

"She has a right to privacy, and I respect that privacy, but if she wants to, I'll be very happy to go to Wellington with her and put the cards on the table in front of the Prime Minister," he said.

"Somebody murdered her parents at Pukekawa and she deserves justice."

Mr Thomas said he never knew any of the detectives involved in the inquiry into the murders, nor did he have any reason to be on the wrong side of them as he had never broken any laws.

Until he read Ian Wishart's book Arthur Allan Thomas: The Inside Story, he believed the murders were "a family matter" with Jeannette Crewe's father, Len Demler, the likely killer.

Wishart's book theorises that Detective Len Johnston should have been a suspect.

"I thought it was a family matter ... but maybe I was wrong," said Mr Thomas.

"It [the book] has widened the net. It was this police officer, who was pretty corrupt."

Mr Thomas went to Pukekawa School with Mrs Crewe and is clearly animated when asked what his memories are of her.

"She was a lovely lady. I thought that she was a nice woman."

He said he never met Harvey Crewe.

The review of New Zealand's most enduring murder mystery has no set time frame.