Teina Pora is poised to ask the Privy Council to quash his convictions for a controversial 1992 rape and murder.
His team is understood to be preparing to seek leave from the Court of Appeal to take an appeal to the top British court, putting on hold his application for the Royal Prerogative of Mercy whereby the Governor-General can refer a case back to the New Zealand courts.
"In the process of investigating the prerogative application we have amassed evidence which makes us believe an application directly to the court to go to the Privy Council is (warranted)," Pora's lawyer Jonathan Krebs said.
"We have even more evidence than we expected we would get that supports Teina's position," Mr Krebs said.
The Supreme Court became New Zealand's top appeal court in 2004 but cases heard by the Court of Appeal before then can be referred to the British court.