It is one of the starkest ethical dilemmas a doctor can face.
Confronted with a patient who is experiencing great suffering, do you help them end their lives and, at the same time, their pain?
The law is clear: actively carrying out euthanasia is illegal.
However, the case of Dr Howard Martin - who told the Daily Telegraph that he hastened patients' deaths out of "Christian compassion" - illustrates the ethical pressures faced by medical practitioners.
Even those with strong moral objections to doctors ending the lives of those in their care admit that some cases can test their resolve.
Dr Andrew Fergusson, a member of the Christian Medical Fellowship and an anti-euthanasia campaigner who served as a GP for 10 years in south-east London, recalls a profoundly disabled patient who asked to be put out of his misery.
"For a moment, my heart said yes but my head said no," Dr Fergusson recalls.
"I'm very thankful that I was able to say to him: 'I can't do that, it's against the law.'
"It's not for doctors to play God. My concern is what a change in the law would mean for elderly and vulnerable people who don't want to be a burden."
Currently, it is this position which holds sway within the profession.
In 2006, the British Medical Association voted by an overwhelming majority against legalising physician-assisted suicide and euthanasia.
But many GPs still believe that the law should be changed.
Dr Michael Irwin, 79, of Surrey, has asked Crown Prosecution Service to charge him after he took a man to a euthanasia clinic in Switzerland.
A former GP, Dr Irwin, one-time chairman of campaign group Dignity In Dying and board member of pro-suicide charity Friends At The End, believes the law prevents doctors speaking freely about the issue.
He says: "I think the question you have to ask yourself is: if you were experiencing great suffering, what kind of GP would you like?
"With any good doctor, in my estimation, your great responsibility is to relieve the patient's suffering.
"If someone is terminally ill and likely to die in a couple of weeks, you don't think, 'Is there a cure?'"
As the law stands in England, Wales and Scotland, deliberate or "active" euthanasia will normally leave anyone assisting suicide or death liable for murder.
Following a ruling in 1993, "omissions" - actions to remove life-saving care - have not been not illegal.
In February 2010, the Director of Public Prosecutions in England and Wales issued draft advice on assisted suicide.
The advice followed the case of Debbie Purdy, a multiple sclerosis sufferer who lost a court case seeking clarification on whether her husband would be prosecuted if he took her abroad to die.
Similar guidelines are expected in Northern Ireland although Scotland does not have a law on such cases.
Independent MSP Margo MacDonald has introduced a bill to the Scottish Parliament to allow people whose lives become intolerable through a progressive degenerative condition, a trauma or terminal illness, to seek a doctor's help in dying.
Ms Purdy, who has MS and campaigns for a change in the law, said GPs were effectively left to make judgements alone because the law prevented them from talking frankly and consulting.
She added: "This just shows us that the discussion has got to be had in public, must be had properly and politicians have got to stop ducking the issue and leaving it to doctors to make their own personal decisions."
But Dr Steve Field, chairman of the Royal College of General Practitioners told the BBC's Today programme there was no excuse for doctors hastening the end of their patients' lives - adding that he was "horrified" that Dr Martin claimed to have done so without their consent.
"What we try to do as GPs is support patients in their last hours, their last days," Dr Field said.
"And if we are finding patients are suffering unduly we can refer and get expert advice from our palliative care colleagues."
The debate will continue. So, too, will the demands of a job whose pressures are as much emotional as ethical.