The Government has ruled out setting up an independent body to investigate miscarriages of justice in the wake of the Teina Pora case.
After 21 years in custody and 11 months on parole, Mr Pora is spending his first day as a free man following last night's ruling from the Privy Council in London.
Justices of the Privy Council quashed Mr Pora's convictions for Susan Burdett's rape and murder in Auckland in 1992.
The idea of setting up a criminal cases review commission has been raised several times, but no government has advanced the idea.
Prime Minister John Key said a commission was not needed.
"Most cases are very correctly judged and where there is doubt, then there is a proper process to go through," he said.
Mr Key said that included the supreme court and the royal prerogative of mercy.
An application for the royal prerogative of mercy is normally considered by the Governor-General only after the appeals process has been exhausted.
Mr Key said the Privy Council had made its decision and any further actions would depend on whether a retrial was ordered.
The Privy Council has called for submissions on whether there should be a third trial for Mr Pora. Crown and defence lawyers have four weeks to argue their case.
Under Cabinet guidelines, if no re-trial is ordered, Mr Pora can apply for compensation for wrongful conviction.
Auckland QC Stuart Grieves said the guidelines' starting point for compensation is $100,000 for every year spent in custody.
Mr Grieves said that would mean Mr Pora could receive in excess of $2 million before any loss of earnings and other factors are taken into account.
Call for 'much more timely justice'
The Labour Party said a criminal cases review commission should be set up because of the length of time it took for Mr Pora to find justice.
Justice spokesperson Jacinda Ardern said Mr Pora languished in prison despite overwhelming public evidence that a miscarriage of justice had occurred.
She said a commission would have provided a far more streamlined process for his case.
"We think an independent body, such as the Criminal Cases Review Commission, would be a much better way of operating that system and could bring much more timely justice when there has been a miscarriage."
Maori Party co-leader Marama Fox supported the call for an independent body, given the Teina Pora case would be one of the last to be heard in the Privy Council.
"Establishing an independent commission to be able to address these types of issues in a speedy way would be beneficial to New Zealand."
University of Canterbury Dean of Law Chris Gallavin said the courts were only able to deal with the case as it was argued but not with new evidence.
He said Mr Pora's situation clearly pointed to the need for an independent review system.
He said most cases were very correctly judged and where there was doubt, then there was a proper process to go through.
New evidence unlikely - Police Association
Mr Pora's lawyer said he hoped police would now focus on who did kill Miss Burdett.
DNA found at the scene linked the attack to the serial sex offender Malcolm Rewa.
Rewa was found guilty of raping Miss Burdett, but two High Court juries could not decide if he also murdered her.
Mr Pora's lawyer Jonathan Krebs said if there was no retrial, he hoped the police may refocus and re-look at their inquiries into their other suspect.
The Police Association said the quashing of Mr Pora's murder conviction had been emotional for those officers involved in the case.
The association's president, Greg O'Connor, said of all the New Zealand cases reviewed by the Privy Council, Mr Pora's had the greatest merit.
Mr O'Connor said the association called for an inquiry in 2013 after some senior officers expressed doubt about Mr Pora's convictions.
"It's been quite a polarising and emotional issue at the moment, for the police who were involved. The fact that there were a number of polarised views on it is why I believed it should always have been subject to a new inquiry."
Mr O'Connor said it was very unlikely any new evidence about Miss Burdett's murder would come to light.
Auckland QC Steve Bonnar said he would be surprised if the Crown now pushed for a re-trial, because there'd be big hurdles to overcome.
"There would be real issues about the major part of the Crown evidence, which is the confessions. That evidence has been the subject of consideration in the Privy Council and, obviously, if there was a retrial, that would be, one anticipates, a major area of evidence for a jury to consider."
Mr Bonnar said re-trying Rewa would also be unlikely.
Meanwhile, a justice advocacy group has said the police have made great advances in questioning techniques but more work is needed to avoid false confessions.
Innocence Project co-founder and co-director Maryanne Garry said suspects typically made false confessions when they were suffering psychological distress and wanted the pressure to go away.
The Victoria University psychology professor said another common scenario was the person coming to believe they did commit a crime, after creating a false memory of an event.
Professor Garry said, thanks to the work of the joint Victoria and Otago University-backed Innocence Project, judges and police now understand how false confessions come about.