A Federal Court judge will decide whether to order the federal government to disclose the reasons behind its decision to extradite accused Nazi war criminal Charles Zentai to Hungary.

Mr Zentai, 88, is currently on bail, living with his family in Perth's southern suburbs, awaiting an appeal against Home Affairs Minister Brendan O'Connor's decision to deport him.

The Australian immigrant is accused of being one of three Nazi-backed Hungarian soldiers who tortured and murdered Jewish teenager Peter Balazs for not wearing a yellow star in Budapest in November 1944.

At a Federal Court hearing in Perth on Friday, Justice Neil McKerracher heard submissions from Mr Zentai's lawyer, Malcolm McCusker QC, that parts of Mr O'Connor's conclusion to his decision had been blacked out.

These needed to be disclosed to the defence to form part of their appeal, Mr McCusker argued.

However, Jeremy Allanson SC, acting for Mr O'Connor, said his client's decision was based on legal advice that it should remain confidential as part of lawyer-client privilege.

Mr Zentai was arrested in Perth in 2005 after handing himself into local police, after Hungarian authorities issued a warrant and extradition order.

The home affairs minister last year announced he would surrender Mr Zentai but the decision was quickly appealed against by his family.

Australian magistrates and federal courts have already ruled there are no obstacles to the extradition.

Another appeal against the minister's decision is due to begin in the Perth Federal Court on March 31.

Outside the court on Friday, Zentai's son, Ernie Steiner, said his father was hopeful all the reasons behind the minister's decision would be disclosed to help his appeal.

He said the family would continue to fight the extradition order all the way up to the full bench of the Federal Court.

"I think it's important that (my father) uses every legal avenue in Australia, because we have that legal system here," he said.

"He wouldn't be afforded that legal protection in Hungary.

"Hungary have not explained how they would provide him with a fair trial.

"They haven't said how they would do that in the absence of any living witnesses.

"How can you provide a fair trial when you can't cross-examine the people who made the statements against you?"

The case against Mr Zentai is believed to hinge on two witness statements from the other Hungarian soldiers involved in the murder, who have since died.

The family's legal expenses in their five-year battle have cost well over $200,000.

Mr Steiner said a foundation had been set up for people to donate to, and that Mr McCusker was acting for Mr Zentai on a pro-bono basis.

Justice McKerracher has reserved his decision.

news.ninemsn.com.au