Kim Dotcom looks close to gaining access to copies of the electronic data seized in the raid on his mansion in 2012.
He faces an extradition hearing, scheduled for February, at which US authorities will ask for him to be sent to America to face copyright-infringement criminal charges arising from the Megaupload internet file-sharing platform.
Computers and electronic data were seized in the police raid at his property in January 2012 and have not been returned.
His lawyers have argued he needs access to his records if he is to counter the inferences US authorities say should be drawn from the "comparative handful" of emails they have selected to use against him.
Dotcom's lawyer, Paul Davison, QC, said in the Court of Appeal in Wellington today the only way to rebut the case against his client would be to demonstrate the selection of documents was misleading. The defence would also have to show that nothing supported the allegation of a conspiracy to infringe copyright.
The three judges have asked both sides to agree terms for return of most of the material.
The hearing has adjourned and may resume later today.