Arthur Allan Thomas has condemned a soon to be released police inquiry into the Crewe murders as a mockery and a "cover up" following the police's defence of the man who led the original investigation.

At a rare public appearance this morning Mr Thomas, who was twice convicted and then pardoned in the murders of Jeanette and Harvey Crewe in 1970, said police were "protecting their own".

"It's a shame that we have this system of cover up," Mr Thomas told the media and members of the public at Pukekawa Hall.

He was flanked by daughter Bridgette and brothers Ray and Des, who called the press conference in response to comments made by Deputy Commissioner Mike Bush during a eulogy at former Detective Inspector Bruce Hutton's funeral last week.

Mr Bush said Mr Hutton was known as having "integrity beyond reproach" and spoke of the "tragedy" of accusations made against him.

Mr Thomas accused Mr Hutton of criminalising the New Zealand Police force and said the former officer and his colleague Len Johnston were corrupt.

"Bush wants to go back and read the evidence. He should do that and not open his bloody mouth."

The 75-year-old said he wanted police to find the real killer and apologise to him but he did not believe either would happen.

"It's a blatant cover up. They have to admit that they fabricated evidence and apologise to me in writing."

Des Thomas said the court of appeal upheld the finding that Mr Hutton and Mr Johnston planted a gun shell casing to frame his brother and police needed to accept it.

The family want an independent investigation into the murders.

- APNZ