The Supreme Court has heard how extraditing an alleged murderer for trial in China puts the man at risk of torture and unfair treatment by the justice system there, despite Beijing's assurances to the contrary.
The request to handover Kyung Yup Kim is New Zealand's first extradition case involving China.
Kim, who was born in South Korea and is a New Zealand resident, is accused by Chinese police of killing a woman while visiting Shanghai in December 2009. He denies the accusation.
The case has been in and out of the courts since China first made the extradition order in 2011. Former Justice Minister Amy Adams twice approved Kim's extradition after seeking diplomatic assurances from China as to his treatment. Last year, the Court of Appeal quashed her decision, raising questions as to the reliability of the assurances. As the process has played out, Kim has spent five years in prison on remand. He's now on bail to his home in Auckland.
In its appeal to the Supreme Court today, the Crown argued the minister knew Kim was at a high risk of torture and would not have surrendered him if the assurances were insufficient.
Through diplomatic channels the New Zealand Government was given assurances by China that it could closely monitor the case, with a representative at the trial, access to copies of interrogation and a guarantee Kim would get a lawyer.
The Crown said the monitoring is a key deterrent to China conducting an unfair trial and if there was a breach it could harm China's international reputation.
"China will know it's being watched," Solicitor General Una Jagose said.
But lawyers for Kim argued any show trial has its problems and rubbished the assurances the Government has been given.
"He would have a lawyer, he would have a lawyer within the system," Ben Keith said.
He questioned how New Zealand would monitor Kim's treatment.
"There are a wide range of torture techniques, some don't leave visible marks."
Kim's lead counsel, Tony Ellis, said it was important to look at how China's criminal justice system works.
He said out of one million criminal charges a year, there are only about 1000 acquittals. Mr Ellis said there was no judicial independence in China.
"We do have faceless judges in China because we have a political committee substituting for judges," Mr Ellis said.