'Witness C' has been sentenced to more than eight years in prison for lying at the double-murder trial of David Tamihere 27 years ago.

The secret jailhouse witness, whose identity remains hidden, gave "powerful" evidence in the 1990 jury trial, which led to Tamihere being found guilty of killing Swedish tourists Urban Hoglin and Heidi Paakkonen.

Tamihere, who described Witness C's perjury convictions as a "major" moment in his case, has always professed his innocence.

Justice Christian Whata sentenced Witness C to eight years and seven months' imprisonment today in the High Court at Auckland in what he agreed was a "truly exceptional" and rare court case.

The maximum sentence for perjury to procure a conviction is 14 years' imprisonment.

Following an August trial in the High Court at Auckland, a jury found him guilty on eight perjury charges.

However, he was found not guilty of obstructing the course of justice, which pertained to his 1995 affidavit recanting his testimony.

Justice Whata revoked Witness C's name suppression today, but an ongoing interim suppression order was made pending the resolution of Witness C's intended appeal of his convictions.

The judge said Witness C's offending had a "high level of premeditation" given the scope and detail of the evidence.

He said the perjury "reveals a level of callousness" and was a "brazen assault on the foundation of our criminal justice system".

Witness C held a "thumbing your nose attitude towards the state" and displayed no remorse, Justice Whata said.

Acting prosecutor Richard Francois said Witness C's offending was the "most serious case of perjury that has ever come before the New Zealand courts".

"This verdict upholds the integrity of the justice system and the importance of the truth on the judicial process," he said.

"The reputation of a nation, defendants, families, the rights of the defendant to affirm his allegiance to society. All of this can be stripped away by evidence falsely presented in a court of law.

"If a man can say whatever he likes in court and not the words he truly feels, then what has he got? This man's at war with the truth, and the justice system is but one of his victims."

Tamihere was found guilty of killing Swedish tourists Urban Hoglin and Heidi Paakkonen. Photo / File

Francois also said the evidence heard at Witness C's perjury trial showed police were complicit in fabricating the evidence.

However, Justice Whata said: "The evidence before me did not suggest, and I'll make this very clear, that the police were complicit."

He added that there was no evidence that it was an "orchestrated campaign" or that Witness C "held a vendetta" against Tamihere.

Witness C's lawyer Adam Simperingham said his client "gained nothing from the perjury" and rebutted the claim that police were entwined in the corruption of the judicial system.

He said there was little to no chance Witness C will commit perjury again, simply because he would not be afforded the chance.

"He has very little credibility and no prosecutor is ever going to call on him to give evidence," Simperingham said.

Witness C was one of three secret witnesses who gave evidence for the Crown during Tamihere's trial.

It is understood one of the secret witnesses has since died, while the other now lives overseas.

The prosecution of Witness C was laid by former prison inmate and "jailhouse lawyer" Arthur Taylor, and aided by researchers Mike and Jenny Kalaugher.

Taylor told the Herald after the trial that he wanted to "send a loud, clear message to jailhouse snitches".

Murray Gibson prosecuted the case at trial on Taylor's behalf.

Despite Witness C's perjury convictions, Tamihere's murder convictions stand after he has already exhausted the judicial appeals process when he was denied leave to appeal to the Privy Council in 1994.

Witness C's jailhouse evidence