Patsy McGrath was surprised to see two policemen turn up on the doorstep of her Nelson home.

She was even more stunned when they presented a warrant to seize her store-bought helium balloon kit.

Acting on directions from Wellington police, the policemen explained they had grounds to believe they would find those materials, which were evidence in respect of a suspected crime: aiding and abetting suicide.

Sean McGrath The helium balloon kit confiscated by Nelson Police.

The 76-year-old has been a voluntary euthanasia advocate since age 25 and is a member of the Voluntary Euthanasia Society and Nelson chapter of Exit International.

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McGrath said she initially found the request from police last Friday amusing and handed over the balloon kit without complaint to the "very polite and courteous" officers who were unaware gas could be used in suicides.

BRADEN FASTIER Patsy McGrath in her Nelson home.

"I think they were embarrassed actually. I didn't bother to make them tell me. I knew more about it than they did.

"I nearly asked them if they wanted my fireworks as well."

What's more, the equipment, which she kept as an "insurance policy", could be easily replaced. The policemen agreed, she said.

However, she later felt angry about the "frighteningly wide" powers police had to intrude on her privacy.

"I thought what an infringement of my rights. They would actually have had the right to pull my house to bits."

A police spokesperson, who refused to be named, said via email that the warrant was served as part of "ongoing police enquiries".

"We are not able to get into specifics at this time," the email read.

Another spokeswoman corroborated what McGrath understood from the visiting officers; She herself was not under scrutiny but rather held evidence relevant to a wider investigation.

McGrath was told the warrant to confiscate her helium tank was the only one issued in Nelson. Police would not say whether similar seizures are underway elsewhere.

She was also given a letter suggesting support services for depression and offering contact details for the "Operation Painter investigation team" at Wellington Central Police Station.

When contacted, police said they were unaware of the operation.

"I think the law should should stay out of my house," McGrath said, adding that she is not causing anyone harm and owning such "toys" is not illegal.

"I just think it's my body, my choice and my responsibility if something goes wrong.

"I've felt it about homosexual law reform, gay marriage and abortion. This battle, voluntary euthanasia, is the one I've chosen for the end of my life."

Not afraid of making herself heard, McGrath has campaigned for choice in many of the social revolutions that shaped modern day New Zealand.

She attended so many rallies and marches in her younger days that she had a generic "virtues" sign to suit all occasions, she said.

But it was her sister's slow death from multiple sclerosis that convinced her she didn't want a life of dependence.

An author and university lecturer in the UK, Daphne was "incredibly courageous" in the face of her diminishing mobility.

"She could blow a straw, moving it up and down, to call a nurse to call a helper to get her to change the channel on the radio to get the music she liked. In the end she had eye movement.

"It was incredibly heartbreaking for everyone else around her," McGrath said. "I just knew I didn't want to live like that."

She said husband Patrick's losing battle with Alzheimer's disease in recent years has been equally hard to bear. He was also a member of Exit International.

"Even though it would be better for my husband to die, I did not think it would be right to help him."

Like more than 21,000 other Kiwis, McGrath has submitted to the current parliamentary inquiry into euthanasia.

She said the freedom to have the right to die would improve society.

WHERE TO GET HELP

Lifeline (open 24/7) - 0800 543 354

Depression Helpline (open 24/7) - 0800 111 757

Healthline (open 24/7) - 0800 611 116

Samaritans (open 24/7) - 0800 726 666

Suicide Crisis Helpline (open 24/7) - 0508 828 865 (0508 TAUTOKO). This is a service for people who may be thinking about suicide, or those who are concerned about family or friends.

Youthline (open 24/7) - 0800 376 633. You can also text 234 for free between 8am and midnight, or email talk@youthline.co.nz.

0800 WHATSUP children's helpline - 0800 9428 787, Open between 1pm and 10pm on weekdays and from 3pm to 10pm on weekends. Online chat is available from 7pm to 10pm every day at www.whatsup.co.nz.

Kidsline (open 24/7) - 0800 543 754. This service is for children aged 5 to 18. Those who ring between 4pm and 9pm on weekdays will speak to a Kidsline buddy, who are specially trained teenage telephone counsellors.

Your local Rural Support Trust - 0800 787 254 (0800 RURAL HELP)

Alcohol Drug Helpline (open 24/7) - 0800 787 797. You can also text 8691 for free.

For more information, contact the Mental Health Foundation's free Resource and Information Service on 09 623 4812.