The lawyer for a woman fighting for the right to die with her doctor's help fears allowing other parties to become involved will turn the case into a euthanasia debate.
Wellington lawyer Lecretia Seales, 42, is taking historic legal action in the High Court, asking it for a ruling which would ensure her doctor would not be charged if she helps her to die.
A statement of claim, filed last month, argues if a doctor cannot lawfully help her die, then she will face a choice between taking her own life or suffering a slow and painful death.
Justice Collins has today heard arguments from the Care Alliance, the Voluntary Euthanasia Society and the Human Rights Commission, who want to be interveners in the case and therefore be allowed to be involved in it.
But Ms Seales' lawyer, Andrew Butler, told Justice Collins the three hours it had taken those three parties to present their arguments today was precisely why they should not be included: it would take too long.
Ms Seales has been told she could only have two months to live.
"I think it's really important we have a reality check on this," Dr Butler said.
"We're not interested in having a big debate about euthanasia. We're not Parliament.
"I'm representing Lecretia Seales, 42 years of age, who is coming to you."
The court had only two considerations when deciding whether to allow the parties to intervene - whether rights and liabilities would be affected by the decision, and whether the court would be assisted by the intervention.
Dr Butler argued Paul Rishworth, QC, for the Crown was extremely experienced and well versed in the Bill of Rights, while he himself knew "a thing or two" about the law.
"Do you really need them (the interveners)," he asked.
Earlier today, Victoria Casey, lawyer for anti-assisted suicide and euthanasia coalition the Care Alliance, told the hearing it was concerned about the effect Ms Seales' action succeeding would have on vulnerable groups in society, such as the disabled and the elderly.
"You need to take into account the voices of the vulnerable," she said.
"You need to hear the voices of the disabled community who say any lifting of that ban puts us at risk.
"These groups feel very strongly that there is a direct and immediate impact on them."
Ms Casey rejected the premise the Attorney General would protect those groups, saying that meant they could not speak on their own behalf.
"They rightly demand their own voice," she said.
Ms Seales talked of unendurable suffering in her application and said it would be appropriate to lift the ban on assisted suicide for people such as herself.
Ms Casey said she was not seeking to minimise Ms Seales' situation but that disabled people suffered the intolerable loss of dignity Ms Seales spoke of every day.
Ms Seales voice would be heard, and rightly so, but it was also important to hear the voices of those who advocated for the elderly, the infirm and the disabled, she said.
"That's why the court should hear from an organisation like the Care Alliance."
Voluntary Euthanasia Society lawyer Kate Davenport, QC, said the declaration Ms Seales was requesting was for people who were mentally competent but who had a terminal illness.
Such a declaration would impact on other members of society but not the disabled as they would have to be competent enough to sign a declaration, she said.
The Voluntary Euthanasia Society was just that - "voluntary" - and it did not advocate euthanasia for those who could not make the decision themselves.
The Attorney General's office had acknowledged it would not be able to present all the evidence needed, and the Voluntary Euthanasia Society would bring a wider range of evidence, Miss Davenport said.
That would include evidence on the way doctor-assisted dying was practised overseas, and from those who had gone through what Ms Seales and her family were going through.
Human Rights Commission (HRC) lawyer Matthew Palmer, QC, said the case would be difficult as there were strong views on both sides.
The HRC would offer an independent and neutral position for the court in the light of those strong views, he said.
Its primary statutory function was to advocate and promote human rights, and this was a case which raised human rights issues.
The outcome of the case would set a precedent which others would seek to challenge, and the court therefore needed to be mindful of wider public policy, Dr Palmer said.
However, the timetable for the case should not be distracted by the three interveners, he said.
Justice Collins reserved his decision. He hoped to release it by the end of this week given the time-critical nature of the case.