A lawyer dying of incurable brain cancer says she is determined to live her life well, while she is still able to, but wants to be given the option to say "enough is enough", a court was told today.

A civil case being heard in the High Court in Wellington was brought by 42-year-old Lecretia Seales, who is dying from a brain tumour.

She says she has the right to end her life with medical help, instead of suffering a slow, painful, undignified death.

Ms Seales wants the High Court to clarify whether a doctor would be committing a crime if they helped her die.

Advertisement

Her case, in front of Justice David Collins, relies 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 unable to be in court when the hearing began today, but did arrive later in the morning and sat with supporters in the jury box.

During his opening speech, Ms Seales' lawyer Andrew Butler gave Justice Collins an intimate look at Ms Seales' life.

Throughout her childhood and adulthood, the word that defined Ms Seales was "determined", he said.

"From a young age she has a keen sense of justice and wanted to make the world a better place."

Ms Seales met her husband Matt in 2003 and they were trying to have children when she was diagnosed with brain cancer in March 2011.

Since then, Ms Seales had remained positive and determined to live her life, Dr Butler said.

"She has been determined to live her life on her terms."

He read out an affidavit written by Ms Seales.

She said while it was "devastating" to be given the diagnosis that the cancer was incurable, she was determined not to fall apart.

"I resolved to live whatever remained of my life as well as I possibly could.

"I knew I wanted to really live while I'm still living," the affidavit said.

Ms Seales said she wanted to be in a position to ask a doctor to help end her life before she was unable to.

"I want to have a choice to be able to say enough is enough."

Ms Seales said she did not know what her death would be like, but it could be slow and difficult.

The idea of being unable to look after herself was unbearable, and she was already finding it difficult to swallow, which sometimes led to choking.

She also did not want to be dependant on strong painkillers, which might not work.

Also joining Ms Seales' case are the Care Alliance and the Voluntary Euthanasia Society.

Today's case was heard in front of a packed public gallery.

About 10 supporters for Ms Seales, including her parents and high profile lawyer Sir Geoffrey Palmer QC, were seated in the jury box.