UPDATED 3.06pm: A former professor of geriatrics is worried Lecretia Seales' case before the High Court will be detrimental to New Zealand society.

The 41-year-old Wellington lawyer, who has inoperable brain cancer, is taking up a case to shield her GP from prosecution if she wants help ending her life.

Former geriatrician David Richmond says it's not just about this one case, but the effect this one case will have on society.

He says in the long run, if euthanasia was decriminalised it would have profound effects on New Zealand society.

Dr Richmond says there're the issues of wrong diagnosis, doctor-patient trust and okaying suicide.

Labour MP Maryan Street believes Ms Seales could well get her way.

"I think the High Court will be very mindful of the recent decision by the Canadian Supreme Court which decided unanimously that it was an infringement of human rights."

"I don't see why people should not be allowed to choose their moment of dying with loved ones around them without subjecting those loved ones to criminal proceedings."