The murder was a simple business. When Rex Arthur Law finally decided he could no longer bear the sight of his wife, Olga, suffering from Alzheimer's disease, he collected the things he needed - eight or nine sleeping pills, a mallet from his garden shed and a pillow.

At 9pm on March 6, he put his wife of 54 years to bed, fed her the pills and waited for her to fall asleep.

He then hit her over the head with the mallet and smothered her with the pillow, before kissing her head and whispering: "I'll be with you soon."

Law, 77, a former dairy farmer and lineman from Thames, waited for an hour to make sure Olga was dead - he did not want her to wake and find him gone - and slashed his wrist with a Stanley knife.

While waiting to die he wrote a suicide note to his only child, John, saying: "Sorry. I can't take it any more. She is getting worse every day. Sell the house and you will get something out of it. Please cremate us and have a private funeral."

But Law's blood coagulated and he did not die. Instead he went to sleep in another room, with a bucket beside the bed to catch the blood. He didn't want to make a mess. He awoke at 4am but decided not to call police.

"I didn't want to get them out of bed," he told the Weekend Herald yesterday. "There was nothing they could have done."

He waited until daylight before he called them, saying: "I've got nothing to live for."

In the High Court at Hamilton yesterday, Law pleaded guilty to a charge of murder and was remanded on bail until August 30 for sentencing.

Justice Tony Randerson granted bail on condition that Law continued to live under the care of his son in Auckland. Defence counsel Matthew Bates said he would be asking for a sentence that did not send Law to jail.

Under the new Sentencing Act, Law could become the first New Zealander convicted of murder to escape a jail sentence. Previously life imprisonment was the mandatory sentence for murder.

But Law is worried that if he is not jailed, it might encourage others to kill.

"I thought I'd be going to jail - murder is a 10-year life sentence - I don't think you should get away scot-free. It could send the wrong message to some people who might do it for money reasons."

He said he was quite prepared to do jail time. "I don't give a damn. You get three meals a day - but I might be a bit old to do too much hard labour," said the former National Party branch chairman.

The murder was a sad end to a typical New Zealand love story that began at a dance hall in Turua on the Hauraki Plains in 1946. Dairy farmer Rex offered to give butcher's daughter Olga a lift home. Romance bloomed.

The couple had one child and ran a dairy farm at Kopuarahi until 1964, when they moved to Thames. Rex joined the power board as a line worker and Olga opened a women's clothing shop, which she ran for the next 30 years.

It was while working at the shop that she met customers whose loved ones were suffering from Alzheimer's. She shuddered at the thought of getting the disease and, says Law, told him: "If it ever happens to me, do away with me."

Law said he agreed and asked her to do the same to him. "It was deadly serious."

About seven years ago Law noticed Olga doing "silly" things, such as putting fish food on the garden instead of in the pond, failing to bank cheques and hiding things all over the house.

Gradually her condition worsened and four or five years ago she was diagnosed with Alzheimer's. Law decided to care for Olga at home by himself, because she would have hated going into a home.

He said the disease got so bad in the last 12 months that his wife no longer recognised him.

She reverted to her childhood, calling for her parents and becoming hysterical when told they were dead. She started using foul language and running out of the house at night, forcing Law to lock all the doors.

He said he decided about three weeks before the murder that he would kill Olga. He used the mallet because he believed it would be the easiest, quickest way. "It was a terribly hard thing to do."

But he knew that his wife would want to be put out of her misery.

"It broke my heart to see her like that. She was such a vibrant, bright person, we were such great mates."

Although he "misses her something terrible", he has no regrets.

"It doesn't haunt me - I've slept well and never had any nightmares. I'd do it again, I wouldn't hesitate."

Law said he would not try to kill himself again (his only health problem is mild diabetes), but wishes he had joined his wife.

"She was so much a part of me, I wanted to go with her. If I go tomorrow I don't give a damn. I shouldn't be here if I'd done the job properly ... The police told me how I should have done it - they're hard shots."

Law said he would also like to see euthanasia laws introduced so doctors could "do the job properly".