But earlier this month, McGrath challenged Ms Collins' "totally unreasonable" decision through a judicial review hearing in the High Court at Christchurch.
His lawyer Phillip Allan said the minister had come to some wrong conclusions in her judgement and raised allegations of bias. He called for his case to be referred to new Minister of Justice Amy Adams.
But Justice Mander rejected McGrath's arguments.
In his judgement, he found the minister was right to trust the Australian criminal justice system to ensure McGrath's rights and those of a fair trial.
"Unsurprisingly, the minister was able to express a level of comfort that there were necessary safeguards in place to ensure that Mr McGrath would be subject to a fair and proper trial process in Australia," Justice Mander said.
Ms Collins accepted that Mr McGrath was not a young man, but concluded there was no evidence that he was of poor health or that it would impact on his ability to defend himself.
She did not think the issues constituted compelling or extraordinary circumstances which would have made it unjust or oppressive for Mr McGrath to be surrendered to Australia.
"On review, I have not been brought to the position where I can conclude that the minister's decision was one that was not reasonably available to her," the judge said.
McGrath's lawyer Mr Allan said today he had not yet had a chance to speak with his client.
He refused to comment until he had talked to McGrath.
NZME. News Service understands that McGrath could potentially take his case to the Court of Appeal.
If no appeal is lodged, Interpol, via New Zealand police, will enact the extradition order on behalf of the Australian authorities.
The Ministry of Justice today referred enquiries to police.
A police spokesman refused to release details of when they may swoop on McGrath and put him on a plane to Australia.
"We will continue to play our part in facilitating the request following the decision from the court," he said.
