The world's leading expert on false confessions says statements that resulted in a 17-year-old boy being twice convicted of a notorious rape and murder "are fundamentally flawed and unsafe".
Teina Pora's self-incriminating statements in the 1992 rape and murder of Susan Burdett came about due to Pora's intellectual impairment and desire to claim a $20,000 reward, Gisli Gudjonsson, professor of forensic psychology at the Institute of Psychiatry, King's College, London, has said in a report seen by the Weekend Herald.
Dr Gudjonsson recently examined nine hours of police video interviews with Pora and visited him in Paremoremo Prison.
His report comes soon after two former senior detectives who worked on the Burdett case came forward with their concerns, prompting the Police Commissioner's office to take an interest in the case.
In 1996, the semen in Ms Burdett's body was linked to Malcolm Rewa, who at the time had a conviction for attempted rape. Rewa was later convicted of sex attacks on 24 women, all committed alone.
Pora has applied for the Royal Prerogative of Mercy, under which the Governor-General can order a new trial.
Assistant Commissioner Malcolm Burgess yesterday told the Weekend Herald that police did not have a view on Dr Gudjonsson's "opinion evidence".
"If the defence elect to present it as part of their application it will no doubt be assessed and considered with all other evidence," Mr Burgess said.
"In due course a decision will be made by others on the merits of the application."
Applications are considered by Justice Ministry officials, sometimes with the help of an independent lawyer.
A Government website says cases "will normally be reopened when new information becomes available that raises serious doubts about a conviction".
Dr Gudjonsson said Pora had psychological vulnerabilities which had been confirmed by recent psychometric tests. This constituted new evidence as that type of assessment was not available at Pora's trials.
"Having evaluated Mr Pora and studied his [police] interviews very carefully, I have no confidence in the self-incriminating admissions he made about his alleged witnessing and participation in the rape and murder of Ms Burdett," Dr Gudjonsson said in the 80-page report.
"I am in no doubt that Mr Pora's self-incriminating admissions are, beyond reasonable doubt, unreliable."
Dr Gudjonsson pioneered research into how people might make false confessions to crimes they hadn't committed during which he identified a range of emotional and psychological factors, such as compliance, suggestibility and personality disorders.
This led him to produce the Gudjonsson Suggestibility Scales which are now used throughout the world when issues of false confessions arise.
Dr Gudjonsson's testimony is credited with overturning the convictions of the Birmingham Six and Guildford Four - groups of people wrongly accused of terror bombings in Britain.
Ms Burdett, a 39-year-old accounts clerk who lived alone, was bashed repeatedly on the head with a softball bat she kept in the bedroom of her Papatoetoe home for her own protection.
The case horrified the public and baffled police who had no firm leads until Pora voluntarily made his inconsistent confessions.
But in 1996, DNA testing showed the semen belonged to Rewa.
Rewa was 39 when Ms Burdett was murdered and had been a senior member of a rival gang to that with which Pora was associated.
Rewa was eventually convicted of raping Ms Burdett but two juries could not reach a decision on the murder charge.
Pora was convicted again in 2000 after a retrial was ordered.
In May, Dave Henwood, a multi-award winning criminal profiler whose expert testimony convicted Rewa of sex attacks on the 24 other women, told the Weekend Herald he has no doubt that Pora is innocent and that Rewa alone attacked Ms Burdett.
He based his view on Rewa's criminal signature, elements of which were present at the Burdett crime scene.
Dr Gudjonsson said his impression from watching the videoed police interviews was that Pora did not know the crime scene and was trying hard to pretend that he did.
The prospect of receiving the reward money and his impaired mental function resulted in Pora becoming entangled in a web of lies, he said.
He was repeatedly caught lying but could not tell the truth if he was to maintain the story of having witnessed the crimes that he hoped would gain him the reward money, Dr Gudjonsson said.
"The longer he lied, the harder it became to own up to having no useful knowledge about the crime whatsoever and to having completely wasted the time of the officers who had been kind to him."
Dr Gudjonsson said the fundamental flaws in Pora's story should have "alerted the police, prosecution, defence and trial judges to their apparent inherent unreliability".
Pora is in his 19th year in prison on a life sentence.