Vulnerable people who were motivated to die for financial or family reasons could take the opportunity to make use of a law that legalised doctor-assisted death, a court has been told.

Today is the final day for arguments in the High Court at Wellington where a potentially groundbreaking civil case over the legality of doctor-assisted death is being heard.

Lecretia Seales, 42, is dying from an inoperable brain tumour and is fighting a legal battle to be able to legally have her doctor assist in her death should her life become too unbearable.

If Justice David Collins rules in favour of Ms Seales, there could be a wide-ranging impact on others suffering a terminal illness.

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The Crown spent the morning finishing its argument that nothing in legislation that allows for doctors to lawfully help to end someone's life and only a change in legislation would make it legal.

Professor John Rishworth QC said there were vulnerable people who may prematurely decide to end their lives should that law be put in place.

"When considering the moral argument, one has to consider the people who may lose their lives if the law was changed."

Those people could be motivated to alleviate the burden they could be on others or to ensure a larger inheritance was left for grandchildren, he said.

Prof Rishworth also argued that in a court of law, "consent is not a defence".

He pointed to Montana law, which said if somebody did assist someone in their death and that person died, the helper could be charged with homicide.

Having liberty did not include a right to die, Prof Rishworth said.

Maybe one day that would be included in the definition of liberty, but it was not there now, he said.

Ms Seales, a former lawyer, is relying on provisions in the Bill of Rights Act enshrining the rights to not be deprived of life or subjected to cruel treatment.

Ms Seales was not present for this morning's court session.

On the first day of the three-day hearing in front of Justice David Collins, she attended periodically throughout the day, sitting in a wheelchair next to her mother and husband Matt near the front of the court, often with her eyes closed while she listened to her lawyers' submissions.

During the duration of the hearing, the public gallery has been packed with members of the public and a handful of Ms Seales' supporters were seated in the jury box.

The Voluntary Euthanasia Society and anti-euthanasia group Care Alliance will give submissions this afternoon.

The hearing is expected to finish this afternoon.

International cases

Assisted suicide and euthanasia has caused controversy in a number of countries.

In Dublin, a case involving the assisted suicide of multiple sclerosis sufferer Bernadette Forde wrapped up after a four-year battle in April.

O'Rorke was on trial for assisted suicide after Forde was found dead in 2011.

According to a recording from Forde, the 51-year-old had decided to commit suicide on her own through fear her friend would face prosecution. O'Rorke was later acquitted.

In Switzerland, a clinic was established in 1998 to help those with terminal physical and mental illnesses die, while they also offer assisted suicide for those with serious conditions. The service is available for anyone.

A referendum in Zurich rejected calls to ban assisted suicide in 2011 by 85 per cent of voters, while 78 per cent of voters rejected a notion to ban assisted suicide for foreigners.