A jury has found a secret witness, who gave evidence at David Tamihere's 1990 murder trial, guilty of lying in court but not guilty of perverting the course of justice.
Witness C, who has name suppression, gave evidence for the Crown, saying Tamihere told him he had sexually molested the Swedish tourists Heidi Paakkonen and Sven Hoglin, killed them and dumped their bodies at sea.
After about eight hours of deliberation, the jury at the High Court in Auckland found Witness C guilty on eight charges of perjury and not guilty on one charge of attempting to pervert the course of justice.
Witness C showed no emotion as the verdict was read.
He has been remanded for sentencing in early October.
Outside the courtroom today, Mr Tamihere said the verdict was a step in the right direction against secret witnesses, but there was still a long way to go.
"We'll have to have a real good look at it, and see what happens after this. This is major for me, and major for the whole concept of secret witnesses, and the way they use them, and the protection that they give them."
Self-proclaimed jailhouse lawyer Arthur Taylor, who brought the private prosecution, said Mr Tamihere's case should be reopened.
"David Tamihere, after waiting over 28 years, has finally received some justice. He, of course, knew all along that Witness C was a bare-faced liar but nobody believed him. Well, now 12 good men and women on a jury have."
Taylor said he had been forced to do the police's job for them.
"I primarily brought the prosecution against secret witness C to send a loud, clear message to jailhouse snitches that if the police, on behalf of whom they gave false evidence, won't bring them to justice, then if I get sufficient evidence, I will."
Taylor said Mr Tamihere should get compensation if his conviction was overturned.
Taylor was represented in court by lawyer Murray Gibson, who said the verdict called into question everything about Mr Tamihere's conviction.
"He should have an opportunity to have the prosecution restate the case against him and give him the opportunity to establish the innocence that he has maintained since day one. It really has called into question a lot of the crucial evidence against David, and he certainly deserves a retrial."
Mr Gibson said he would now be pushing for Witness C's identity to be made public.