Witness C has filed an appeal against his conviction and sentence for lying at the double-murder trial of David Tamihere 27 years ago.
Papers were filed yesterday with the Court of Appeal by a lawyer on behalf of Witness C.
The grounds cited were that "the verdict was unreasonable and not supported by the evidence" and the "sentence is manifestly excessive".
The secret jailhouse witness gave what the prosecutor in the perjury trial called "powerful" evidence in the 1990 jury trial, which resulted in 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. Tamihere spent 20 years in jail before being released on parole.
In sentencing Witness C to eight years and seven months jail in October in the High Court at Auckland, Justice Christian Whata agreed with prosecuting counsel that it was a "truly exceptional" and rare court case.
Perjury carries a maximum sentence of 14 years' jail.
A jury found him guilty on eight perjury charges after a trial in August.
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".
Justice Whata lifted Witness C's name suppression but on being informed that he planned to appeal, granted interim name suppression.