Benson was not all that surprised. The affable Footscray GP had treated the woman and her son for years and she had already told him she had no intention of being kept alive through the final stages of glioblastoma – a frightening cancer that can distort one's personality in distressing ways.

The woman was in her 80s. She had lived an independent life, and wanted the same sort of death. She had already told Benson that she did not want to reach a point where she could not look after herself. Her son was now living interstate. She wanted him to do this one last thing for her.

"I told him to give her a big dose of morphine[and another drug] she had while she was in palliative care and to put a plastic bag over her head,"Benson says. "He said, 'If that's what I have to do, that's what I have to do'."

Taking lives, rather than saving them, is not something many doctors aspire to. But the old adage "first do no harm" has been challenged in recent years by euthanasia campaigners Rodney Syme and Philip Nitschke who say they have both helped countless people die when they thought it was the most compassionate thing to do.

It is unclear how many doctors make similar decisions each year. In 2007, a survey of 854 Victorian doctors found that 302 had been asked at least once to hasten someone's death by giving them drugs. Of that number, about a third said they had agreed.

While few doctors have spoken publicly about such cases, three Melbourne doctors have decided to reveal their experiences in The Sunday Age because they believe physician-assisted death should be legalised. In Victoria, euthanasia and assisted suicide are both illegal, carrying penalties of up to 25 years' jail. So far, no politicians have announced any plans to examine legalisation ahead of this year's state election.

Another doctor. Another mother. Before he retired, Peter Valentine was a cardiologist. He looked after people's hearts. But this did not help much when it came to caring for his own mother in her final years as she endured the severe pain and immobility of rheumatoid arthritis. That task fell to her GP.

Valentine says that when she became too weak to walk and feared being unable to remain in her home, the 81-year-old told her GP that she did not want to go on. Valentine believes that what happened next was not an accident. The GP gave her a cache of strong sedatives and advised her that a certain number of tablets would be "a very dangerous dose," Valentine says. "So I'm certain he knew."

About three months later, Mrs Valentine asked her son to be with her in her Hawthorn home. The two had spoken on several occasions about her wish to die. Valentine was convinced she was sane and rational. She was not depressed. Her condition was incurable. And she was only going to get worse.

"She took her life with my help in the sense that I was present and I handed her the tablets," he says.

She breathed for about five more minutes, Valentine says. And then she stopped.

"I held her as she died ... and I knew it was an infinitely better death than the one staring her in the face," he says.

Later, he called his mother's doctor to come and confirm the death. The death certificate the doctor wrote listed her various medical conditions. It did not mention the overdose. He thinks this happens a lot.

"I think this is a similar subject to abortion in the 1960s. Everybody was trying not to see the problem, they were kind of sweeping it under the carpet. They didn't mind it happening so long as it wasn't public and did not rise to the surface," Valentine says.

Another doctor. Another death. A Melbourne GP who does not want to be named says she had known a woman for about a decade when she came to her one day feeling breathless. Scans revealed terminal breast cancer that had spread to her lungs.

After seeing an oncologist, the woman told her GP that she had no interest in letting the tumours slowly claim her life. Instead, she had one request: A syringe pump with enough morphine in it to die gently with her family around her.

"She was a charge sister, a nurse, she was used to controlling other people's lives and she wanted to control her own," the GP says.

Over the following days, the GP spoke with the woman's siblings who understood their sister's view and supported her decision.

By the end of the week, the family was gathered in a small private hospital room. The GP prescribed enough morphine for 24 hours that could be used in one hit. When she left, the woman said goodbye to her loved ones, pushed the pump repeatedly, and slipped away in a deep sleep.

The next day, her siblings visited the GP to thank her.

"They said it was lovely and that they would never make any trouble about it because they understood that that was clearly what she wanted," the doctor says.

"I personally think this is happening all the time, it's just that the media are not hearing about it."

Like Mrs Valentine, there was no mention of suicide or euthanasia on her death certificate.

While all of the doctors who spoke to The Age say it is shameful that seriously ill people do not have equal access to doctors who will help them end their lives peacefully when the time is right, they believe secretive and unregulated assistance has its dangers, too.

For some, this was recently highlighted by the Medical Board of Australia's suspension of Philip Nitschke's registration to practise medicine. Nitschke says the board took the action against him because of discussions he had had with Nigel Brayley, a 45-year-old man who sought his advice while police investigated the suspicious death of his wife. Brayley was not physically ill when he took his own life earlier this year and there are now suggestions he was depressed at the time.

"There needs to be some control over it and at the moment we're getting into a situation where the means are there and uncontrolled," Benson says.

As for the man wanting to mercifully kill his mother, Benson believes it was right for him to offer the advice he gave. He says the woman had clearly stated her wishes to him and that her son was grateful for the conversation, even if it left him in an invidious position.

"I had known both of them. It was not a situation of knocking off mum for her millions. And why knock off mum for her millions? She was going to die within six months anyway. She may have been a burden, but it was obviously a very temporary burden," he says unapologetically.

"I try to do the best for people ... but best to my mind does not necessarily mean living as long as you possibly can. If life is intolerable and you know it's not going to get any better then there's no point in persisting with it."

Benson does not know what happened to the woman and her son in the end, mainly because the pair were living together in another state. He says their situation highlights the unfortunate reality of limited end-of-life choices in Australia.

"This is a big issue and it's about choice," he says. "It's not about forcing anybody to do anything. It's about giving people the option if they need it. Lots of people would like to know it is available."

For help or information visit beyondblue.org.au, call Suicide Helpline Victoria on 1300 651 251, or Lifeline on 131 114