Although the 78-year-old widow still weeps as she remembers the events of 1956, she fully supports Professor Sean Davison, who faced the same dreadful choice in 2006.

His mother, who lived in New Zealand, had terminal cancer, and he helped her die.

Davison's case hit the headlines - as did that of Joseph "Joe" Davidow of Yeoville, Johannesburg, 56 years ago.

Davidow shot his mother, Minnie, and was later acquitted by a jury who found he had acted out of a sense of compassion.

Izikowitz said coverage of Davison's trial in New Zealand hit closer to home than many realised .

In January 1956 her brother shot their mother.

''My mother suffered from terrible arthritis," the widow said.

"She was in a wheelchair for four years. Her hands were deformed and she was in tremendous pain."

Izikowitz said her brother was "tormented" by their mother's misery, and he warned the family that he would help her die.

''But we didn't believe him," she said.

"He was so good to her. He would feed her breakfast every morning and take her supper after work while she was at Edenvale Hospital."

But on January 27 Izikowitz was summoned to the hospital to see the superintendent.

She said: ''When I got there, they told me my mother had been shot. I knew it was Joe.

"He had asked the hospital staff to move her bed to the balcony. She pleaded with him to shoot her. He put the gun against her temple and pulled the trigger.

"And then he went to the hospital staff, handed over his gun and told them to call the police," she sobbed.

She later learnt her brother had waited until a few days after his younger sister's birthday before the mercy killing, because "he didn't want my birthday to be associated with our mother's death".

"He said he would never do that to me," Izikowitz said.

In Davison's case, his mother, Patricia, had stopped eating in a futile effort to hasten her death, but had eventually begged her son to help her die.

Izikowitz said her brother was arrested for murder and the family faced severe public criticism.

''It was a different time then. Joe was considered a murderer. But, as a family, we supported him. He did what we couldn't.

"He went on trial and the court acquitted him on the basis of a mercy killing," she said.

Davison was also put on trial, but a New Zealand judge found he had been motivated by compassion and love, and sentenced the forensic scientist to five months of house arrest.

Joe Davidow died 12 years ago from a brain tumour.

In 1956 the Sunday Times quoted unnamed lawyers as saying "there has seldom been a case in which the reports of psychiatrists have been of such importance to the defence".

It quoted Davidow as saying: "I very much resented the tests by psychiatrists. I'm normal, I told them. I told one psychiatrist that I regarded the whole thing as a lot of nonsense."

Izikowitz said of the Davison case: ''I was so heartsore when I read about Professor Davison. He should not be ashamed. He did a most wonderful thing."