Lecretia Seales, the Wellington woman who fought for the right to die on her terms, has died. She was 42.

Photo: Facebook/ Lecretia's Choice

A statement on behalf of her family said she died at 12.35 this morning, of natural causes.

A former Law Commission colleague Cate Brett said Ms Seales died with her husband and parents beside her.

"Last night about 11.30 Lecretia started having trouble with her breathing so the family called the district nurses to come in and assist and they were actually en route to Lecretia's home when she ceased being able to draw breath at about 12.35 this morning."

Ms Seales was still in good spirits leading up to her death, she said.

"She was still able to smile and you know obviously engage with those around her and certainly she did not suffer a prolonged and painful death, and so on that count I think the thousands of people who have been supporting and sending love to her family will be heartened by that."

Ms Seales shot to prominence this year when she took legal action in the High Court asking that her doctor be allowed to help her die, without then being prosecuted for doing so.

The court ruling will be released by her family at 3pm today.

Former Prime Minister Sir Geoffrey Palmer said Ms Seales was an unselfish person who turned her painful experience into a law reform project.

Sir Geoffrey, who was a former colleague of Ms Seales, said he was sad, but relieved she did not experience a slow, painful death as was feared.

"The worst things that could have happened to her - to have a long lingering and terrible death - did not happen to her.

"I think in some ways she was with her family and was relatively peaceful."

Sir Geoffrey said any legislation implemented on the right-to-die should be her legacy.

He said whatever the result of the case, it was clear a new law was needed.

"If this problem is to be cured then there needs to be legislation, the form that legislation takes, the framework that is put in place is the matter that now concerns us, and that should be Lecretia's legacy."

Ms Seales' action was prompted by the diagnosis of a brain tumour in 2011.

Her health deteriorated over the next four years and in May 2015 her oncologist described her as having "no more than weeks, or a short number of months" to live. It turned out to be weeks.

Ms Seales told Radio New Zealand in March she was usually a private person.

"(But) the more I thought about the right to assisted dying, the more I believed in the cause and for the greater good I let my personal details become public," she said.

"The fact that I am a lawyer, I have been involved in lots of law reform and I have a terminal illness kind of puts me in a prime position to be a leader on the subject."

Ms Seales had decided by the age of 11 to be a lawyer, her own lawyer, Dr Andrew Butler, said during the court case.

Photo: SUPPLIED

She grew up in Tauranga, the big sister to Jeremy and Katrina, eldest child of Shirley and Larry Seales, before heading off to Wellington's Victoria University.

Her first legal job was with Kensington Swan but the bright lights of London soon beckoned and she headed off on a two-year OE.

High-profile firm Chen Palmer took her on when she returned to Wellington in 2002, and she stayed there until finding her "true home" at the Law Commission in 2007. It was, Dr Butler said, a place she could combine her passion for law, reform and social justice.

But life wasn't just about work; she met husband Matt Vickers in 2003 and the two later married.

They planned to have children but it did not happen easily, and it was while they were exploring parenthood options that Ms Seales was diagnosed with brain cancer.

"I'm very lucky. I'm unlucky to have got the cancer but since I've just had amazing support from my family and friends," Ms Seales told Radio New Zealand.

But still she feared what would happen when she declined, when she became incontinent and would have to rely on others to do everything for her.

"I have a fantastic life at the moment. I don't want to end it right now by any means but I do worry about what will happen when I decline.

"I guess it's fear of suffering and I've seen older relatives really suffer with cancers at the end stages and I don't want that for me. I just don't want to lose my mind because it's been such an important part of my life."

"It's part of everyone's life but I've been lucky to have a good mind and fear of losing that is big."

Photo: TVNZ

Angela O'Meara met Ms Seales at intermediate school 30 years ago and told Radio New Zealand their friendship had grown as they did.

"It's obviously something that she felt very strongly about, and there's no doubt that her health has deteriorated during the course of bringing the case and certainly since the hearing," she said.

"But she's a really strong lady. She's a determined lady. She's got a strong moral compass. If anyone can do this, it's Lecretia, despite the difficult timing."

Dr Butler repeatedly spoke in court of Ms Seales' determination, and it was that determination that got her to court to hear him fight for her right to die on her terms in her final weeks.

The woman who loved to dance, travel, cook, bake and entertain, who studied Te Reo, German and Italian, sat in a wheelchair, eyes closed most of the time, and listened to the fight for her life.

That life ended early this morning just after midnight, but her legacy lives on.