David Bain's lawyers are arguing that Justice Minister Judith Collins has already broken legal privilege in dealing with his compensation claim, so shouldn't be using that as a defence in court.
Mr Bain spent 13 years in prison for murdering his family in Dunedin in 1994, but was found not guilty at a retrial in 2009.
The lawyers are fighting for access to advice Ms Collins received about the compensation bid after a report from retired Canadian judge Ian Binnie said that, on the balance of probabilities, David Bain was innocent. Ms Collins had the report reviewed by a Queen's Counsel.
Mr Bain's lawyer Michael Reed, QC, told the hearing in the Auckland High Court on Tuesday that Judith Collins abused her power, breached natural justice and pre-determined the claim.
He read an email from one of Ms Collins' staff, telling the minister and another colleague to keep the retired judge on side in case he turned "feral" on them.
Mr Reed said Ms Collins has already broken legal privilege, which is expected to be her defence, by releasing the Solicitor-General's advice to police and the lawyer asked to review the judge's report.
He told the court that another minister needed to look at the compensation claim, because Ms Collins could not distinguish between her role as the Minister of Justice and her previous role as Police Minister.
Mr Reed said he believed the claim had been hijacked by police and Crown Law, and Ms Collins would not release the documents because they had something to hide.
He said the Crown had been drip-feeding some documents, which had previously been classified as legally privileged.
The Crown will defend the minister in court on Wednesday.