A secret jailhouse witness who lied at one of New Zealand's most notorious murder trials can now be unveiled.

His name is Roberto Conchie Harris.

After lengthy court proceedings, the Herald can reveal today that Harris, who has been convicted of perjury for lying at David Tamihere's 1990 trial, is also a double murderer and sex offender.

Tamihere was sentenced to life imprisonment in December 1990 for the backpacker murders of Swedish tourists Urban Hoglin, 23, and Heidi Paakkonen, 21.

His conviction came, in part, on the back of "powerful" testimonies from three secret jailhouse informants.

They were known as "Witness A", "Witness B" and "Witness C".

The prison witnesses all claimed Tamihere had, at different times and while in custody, confessed to how he sexually assaulted and killed the Swedes.

David Tamihere has described Witness C's perjury convictions as a "major" moment in his case. (Photo / Jason Oxenham)

The Herald can further reveal that Harris claimed he met Tamihere while Harris was in prison for the double-killing of Northland couple Carole Anne Pye and Trevor Martin Crossley.

Pye's three children, then aged 10, 9 and 7, found their mum and her partner's bodies with gunshot wounds to their heads when they returned home from school on February 22, 1983.

Police tracked down Harris as the killer. He was later found guilty of their murders by a jury in the High Court at Whangarei.

At Harris' trial, his girlfriend infamously testified that Harris told her that killing the couple was "just like having an ice cream''.

Roberto Conchie Harris at his sentencing last year. (Photo / Peter Meecham)

Last year, in a rare private prosecution by "jailhouse lawyer" Arthur Taylor in the High Court at Auckland, Harris was found guilty of lying at Tamihere's trial.

A jury decided he was guilty on eight perjury charges but not guilty of obstructing the course of justice, which pertained to his 1995 affidavit recanting his murder trial testimony.

When sentencing Witness C to eight years and seven months' imprisonment last year, Justice Christian Whata also revoked Harris' name suppression which has stood for nearly 30 years.

However, the judge made an interim suppression order after Harris indicated he would appeal his perjury convictions and sentence.

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

The case then went to the Court of Appeal, while the issue of Harris' name suppressionalso went to New Zealand's second highest court.

Then, earlier this month, Harris' lawyer Adam Simperingham issued a notice of abandonment for the appeal of his client's perjury convictions.

This meant Harris had dropped his appeal against his perjury convictions - opening the door for him to be named for the first time.

Justice Whata said, given the developments, he was minded to revoke his suppression order but allowed Simperingham and the Crown to make their arguments first.

Simperingham accepted that because Harris had abandoned the appeal it would be appropriate for the court to confirm the suppression order has lapsed.

Today, Justice Whata revoked his interim suppression order, unmasking Harris as Witness C.

David Tamihere photographed at the time of his trial. (Photo / NZ Herald)

Hoglin and Paakkonen disappeared in April 1989 and had left their car at the end of the Tararu Stream road in the Coromandel Ranges.

It sparked the largest land-based search ever undertaken in New Zealand.

In 1991, Hoglin's remains were discovered by pig hunters in bush near Whangamata, about 70km from where the murders were alleged to have taken place.

Harris had testified that Tamihere told him the bodies were dumped at sea.

Paakkonen's remains have never been found.

Tamihere spent two decades in prison for the killings but has always professed his innocence.

Last month, Taylor also targeted a second witness in the Tamihere trial - Witness B.

The Crown opposed the application, but Justice Mark Woolford revoked the suppression order made on November 20, 1990, by trial judge Justice David Tompkins.

It will come into effect from May 1, to allow the Crown to seek further legal options.

Researcher Mike Kalaugher, along with his wife Jenny, have aided David Tamihere during the court process. (Photo / Jason Oxenham)