The Greens have joined the Maori Party in calling for a review of the jailing of Teina Pora, who has served 20 years for the rape and murder of Auckland woman Susan Burdett.
Green Party justice spokesman David Clendon has written to Police Commissioner Peter Marshall to demand an investigation into the prosecution and conviction of Pora for the 1992 murder.
He was responding to a documentary made by Auckland filmmaker Michael Bennett shown on Maori Television last night.
The documentary featured experienced barrister Marie Dyhrberg, who revealed that of all her cases she believed most strongly that Pora was innocent.
Mr Clendon said serious misconduct by police was rare in New Zealand, but he felt it was important to maintain the public's faith in the justice system by holding a review.
"It's not only important for the stakeholders in this case, but for people watching that documentary - they're going to have to wonder about the integrity of the justice system if a case like this can lead to a 20-year sentence.
"People need to be confident that the justice system will respond when new evidence comes to light, or where some doubt is cast on a prosecution. Whether the conviction is found to be valid or invalid, at least we'll get an outcome that people can believe in."
Pora's conviction in 1994 was based on his contradictory statements and testimony by witnesses, at least three of whom were paid by police.
Mr Clendon: "It seemed extraordinary that the original so-called confession was ever considered valid. [Pora] obviously had no clue about what had happened or where, and couldn't identify the victim in any way."
Pora was found guilty at a retrial in 2000 which came after the semen in Ms Burdett's body matched the DNA of Malcolm Rewa, a prolific rapist who usually attacked alone.
Maori Party co-leader and Associate Minister of Corrections Pita Sharples said in March that he supported a royal prerogative of mercy to reopen Pora's case after a separate documentary on TV3 shed new light on possible inconsistencies in the conviction. That documentary followed Herald investigations into the case.
A royal prerogative requires the Governor-General to refer a case back to the courts.
Justice Minister Judith Collins said last month that the Ministry of Justice required more information from Pora's lawyers before any decisions about a prerogative of mercy could be made.
Pora's legal team is now believed to be putting an application for a prerogative of mercy on hold and is instead seeking to have the conviction quashed by the Privy Council. Court of Appeal cases heard before the establishment of the Supreme Court in 2004 can be referred to the Privy Council, the highest British court.