Police have hired one of the country's top lawyers to investigate a former officer's stunning confession that he lied in court - and wrongfully sent at least 150 people to prison.
Patrick O'Brien wrote to Chief Justice Dame Sian Elias admitting to perjury, saying he was racked with guilt after carrying a "dreadful secret" for more than 30 years.
Now nearly 60, O'Brien was an undercover agent in covert drugs operations in the 1970s, immersed in a dark, criminal underworld, and the star Crown witness in the resulting court trials.
However, O'Brien says he lied on oath every time he took the stand.
In the confession letter, he said he could not guess the number of people with convictions or imprisoned "because of my lies", because he stopped counting arrests at 150, halfway through his three-year stint.
All but one of the juries - in a case where the Crown failed to prove a substance was a narcotic - returned with a guilty verdict.
Leading Wellington lawyer Bruce Squire, QC, has been hired by Police National Headquarters to investigate the allegations independently.
Squire, who also investigated allegations into the police undercover work in 2004, did not return Herald on Sunday calls.
In his confession, O'Brien told Dame Sian he answered to the "grey men" who trained him, on whose orders he lied to obtain the convictions at any cost.
"They called it Doomsday work and instructed me to take this dreadful secret to the grave," O'Brien wrote.
"In every case I lied to the courts and I lied to the juries to obtain convictions against my targets.
"Telling lies was easy - 'policemen don't tell lies' - and my targets never stood a chance."
Tampering with evidence was also common, he said. Often the exhibit before the court was not the drugs that he bought from the target.
He also deceived his operators, usually high-ranked detectives stationed in the communities where O'Brien operated undercover.
"Most of these men were tough (real tough) but without exception they were honest and would have brooked no time for the methods I employed to obtain convictions," O'Brien wrote.
Eventually, the shame and stress of the work broke O'Brien. He resigned from the police and fled New Zealand, "haunted, traumatised and scared".
"My life since has been a tragic waste; running, always running, but never able to lose the demons that rush around in my head.
"I am nearly 60 years old now, and in what time is left to me, intend correcting the wrong I have done."
O'Brien was honoured for his undercover work by former Governor-General Sir David Beattie, who presided over a series of drug trials held in the High Court at Hamilton in 1974.
Sir David wrote to Police Commissioner Ken Burnside with a glowing testimony about the young constable who was such a credible witness, despite defence counsel questioning his truthfulness.
Later asked why he wrote to the commissioner, Sir David told a radio show host he was "impressed with the standards this man had set himself, and the risks he had run, and the results he achieved".
O'Brien confessed to Dame Sian: "In every case and on every charge, I lied to Sir David and I lied to his juries."
His confession letter was obtained by the Herald on Sunday through the Official Information Act.
Police National Headquarters received the letter on Christmas Eve, but an investigation did not begin until February.
Police spokesman Jon Neilson would not comment further until the investigation was complete.
O'Brien said he would co-operate fully with the inquiry and plead guilty to any charges.
Yesterday he told the Herald on Sunday he was "a homeless itinerant" currently hitchhiking in the South Island.
"I am not in hiding, nor am I running."
In his confession he said he intended to "start knocking on doors and apologise" to those he had helped to wrongfully convict.
"Should any target wish to seek remedy for my wrong, I will assist in whatever way I can."
He was not surprised he had not been interviewed by Squire, despite almost 300 days passing since his confession.
He had posted open letters on websites and paid for adverts trying to make contact with his former targets.
"Following orders is no excuse, I knew what I was doing was wrong," said O'Brien.
"Now I will face the truth."
The inquiry terms of reference:
Leading lawyer Bruce Squire QC's terms of reference for the inquiry require him to:
Identify and clarify that Patrick O'Brien lied and tampered with evidence.
Assess the implications and veracity of the allegations.
Determine whether the police should investigate further.
He will report his findings to Police Commissioner Howard Broad. Even if it can be proven, the people convicted and imprisoned on O'Brien's false evidence may not necessarily be eligible for compensation.
Cabinet has a base sum of $100,000 awarded for each year wrongly spent in jail, though that amount can be higher.
However, rules introduced 10 years ago mean compensation is awarded to those wrongly convicted only if they can prove their innocence beyond reasonable doubt.
Arthur Allan Thomas received $1 million in 1980 for the 10 years he spent in jail. David Dougherty was awarded almost $900,000 in 2001 after DNA evidence proved him innocent.