Greg Ward BBC in Auckland

Lesley Martin wrote a book about her experience

A nurse in New Zealand who has campaigned for voluntary euthanasia is now on trial charged with the attempted murder of her terminally ill mother.

40-year-old Lesley Martin is the country's best known advocate for euthanasia.

She could face up to 14 years in jail if found guilty of attempting to kill her mother by suffocation.

The attempted murder charge dates back to 1999 when Lesley Martin's 69 year-old mother was dying of bowel cancer.

Ms Martin cared for her mother for five months before giving her an overdose of morphine and later smothering her with a pillow.

The woman died the following day.

Three years later Martin published a book about the experience, saying her actions were in keeping with her mother's wishes.

It was after reading the book that New Zealand police decided to pursue a homicide investigation.

Ms Martin was arrested and charged with attempted murder.

The case has caused widespread debate in New Zealand, where euthanasia was the subject of a parliamentary vote only last year.

A proposed new law which would have legalised euthanasia was narrowly defeated despite support from the prime minister.

The Lesley Martin trial is expected to last two weeks.

Although she could face a maximum of 14 years in jail if found guilty, analysts say a more likely outcome is a sentence closer to two years, perhaps served as home detention.

Since her mother's death, Lesley Martin has established Exit New Zealand, a pro-euthanasia lobby group.