But after his elderly cancer-ravaged mother summoned him home from South Afri' />

No one knows the name Sean Davison, and that's the way he likes it.

But after his elderly cancer-ravaged mother summoned him home from South Africa to help her die, Davison has grimly determined that he must take a public role in the campaign to legalise assisted suicide.

The Auckland-born scientist arrives back in the country again today, ahead of the publication of his new memoir, Before We Say Goodbye.

It is adapted from diary entries Davison, 47, made in the last months of his mother's life. He will use the book launch to push for the legalisation of physician-assisted suicide.

The book describes how 84-year-old Patricia Davison, a former GP and psychiatrist who practised under the name Fergusson, tried to end her life by going on a 35-day hunger strike - but she survived.

"One of the messages is that we don't all die peacefully in our sleep," Sean Davison told the Herald on Sunday.

"My mother's death wasn't peaceful, and the way she planned it back-fired. If she'd had an alternative, she would have taken it."

Patricia Davison finally died in her Dunedin home in October 2006, her son by her side. Her death was not the subject of a coroner's inquiry, and her son refuses to say exactly how she died.

He emphasised: "There is nothing in the book to incriminate me. And I won't be implicating myself when I'm in New Zealand. It's actually irrelevant whether I did or didn't; that's not the point. The point is, I should never have been in that situation."

Yesterday, Brendan Malone from Catholic organisation Family Life International said legalising euthanasia was a "dangerous idea".

Instead, doctors should have better training and resources for pain management.

"Someone at the end of their life should not be left to die in agony, but euthanasia is not the answer to that problem. The answer is to resource properly for palliative care."

Davison lives in South Africa, where he is a professor of biotechnology and heads a forensic DNA unit that helps resolve human right abuse cases. He was raised in Hokitika and attended the University of Otago.

He said he was grateful to independent publisher Christine Cole Catley for her tenacity as the book passed through legal hurdles - including certain tactical deletions.

In a series of speeches he will argue that people should be able to choose how they die.

"If a person wants to die, if they do it through clinics that have all the checks and balances to make sure there are no pressures and they're making a conscious decision, why shouldn't they?

"I'd like to choose my time. It should be an individual decision."

Lesley Martin, a former nurse from Wanganui, was jailed in 2004 for giving her cancer-suffering mother an overdose of morphine and smothering her with a pillow.

She warned Davison about joining the controversial euthanasia law reform campaign.

"Once he makes himself a target for this issue, people will have expectations of him," she said. "On one hand, I think the more people that speak out the better, but I do know what he's entering into."

She added: "It's a fundamental human right to make decisions on your dying process. The will to live is deeply ingrained, but if someone's lost that will that's something that neither we, nor palliative medicine nor religion can fix."

Former NZ First MP Peter Brown's private member's bill seeking to legalise doctor-assisted suicide, was defeated by three votes in 2003.

He said yesterday that it was time to reopen the debate. "The time has come to at least put it on the agenda and have a genuine, meaningful debate," Brown said. "Whether we like it or not, we've all got to depart sooner or later. Why should people depart in terrible circumstances and suffering?" additional reporting Heather McCracken

- ADDITIONAL REPORTING: Heather McCracken