The law of "double effect" allows doctors to administer painkillers such as morphine to alleviate suffering at a dosage they know could also kill the patient. As long as their intention is to reduce pain doctors are exempt from prosecution.
Dr Moor ended up in court because he said he had helped elderly patients to die. By stating that his primary intention was to shorten life he left himself legally vulnerable and was prosecuted for murder.
He had spoken in support of Dr Michael Irwin, chairman of the Voluntary Euthanasia Society, who claimed in a newspaper he had helped at least 50 terminally ill patients to die.
Dr Irwin had said he prescribed large doses of sedatives then placed a large exit bag with an adhesive neck seal over the patient's head. Dr Moor said at the time, that although he would not use a plastic bag to suffocate patients, preferring more humane means, he "aggressively supported" what Dr Irwin was doing.
In July 1997, Dr Moor told a journalist he had helped two patients to die in the previous week and did not have a problem with helping them to die. Police then investigated the death of George Liddell which led Dr Moor being charged with murder a year later.
His trial has highlighted the difficult dilemma doctors face with terminally ill patients who want to take drugs which will hasten their death. "It has been a terrible 18 months for family doctors who find themselves with a terminally ill patient in great pain" said Dr Vivien Sleight, a GP from Hertfordshire.
"It is hypocritical and has put many patients and doctors in a difficult position. Patients who have known their doctors for a long time do not want to ask them for help to die because they are afraid of their doctor being charged with murder."
Dr Sleight believes the law needs to be changed to allow patients the right to say they want their doctor to help them to die. "At the moment they can instruct their doctor not to give them treatment, in the form of an advance directive or living will, but they cannot tell them what treatment they want," she said. Some 100,000 deaths a year in the UK are believed to be hastened by the "double effect".
Dr Michael Wilks, chairman of the Medical Ethics committee, of the British Medical Association, said although Dr Moor's case had made many doctors nervous about their position, the majority of doctors were very clear about their intentions when treating the terminally ill. "I have hastened death in my general practice," he said. "I have hastened death because at the time I have made a decision about the amount of pain reliever to give to alleviate the symptoms, and that dose of pain reliever has shortened life. As long as the primary intention is to relieve pain rather than hasten death, then the doctor is carrying out proper palliative care."
Many doctors have openly admitted helping patients to die but Dr Moor was the first to be prosecuted for murder.
Dr Irwin wants to see a change in the law. "Slow euthanasia where regular drugs are administered over two or three days does go on in this country. Dr Moor may have been slightly foolish in admitting to it but most doctors do it," he said.
Dr Christopher Hindley, a London GP, has assisted up to 10 patients to die at their request. He also believes it is hypocritical that many GPs hide behind the doctrine of double effect when the real intention is to shorten life.
Dr Peggy Norris, of Alert, a pressure group opposed to euthanasia said: "It is not a simple matter of law - it is an ethical and moral issue."
Attitudes to euthanasia
The Netherlands: Voluntary euthanasia decriminalised 1984; 3,000 a year die in killings that must meet strict criteria. Parliament considering legalising euthanasia.
Switzerland: Loophole in law allows people to die under tightly controlled circumstances.
Italy: All forms of assisted dying remain illegal.
France: Strong resistance till recently but debate sparked last year after nurse admitted 30 mercy killings.
Canada: Strong campaign to relax law but it has failed to get euthanasia legalised.
Australia: Northern Territory introduced law legalising euthanasia in 1996 but it was overturned in 1997 by the federal parliament. Four people committed euthanasia.
US: In Oregon, doctor-assisted suicide, backed by a referendum, has been legal since 1997. Elsewhere the practice is illegal.
Africa: Not generally seen as big issue but officially remains illegal. Zimbabwe is one of a few countries where it seems to be discussed publicly.
Japan, China: Debate is now taking off seriously for the first time. Remains illegal.
Russia: Still illegal and not thought to be issue which has caught public's imagination.
Lack of information suggests it is a low-key concern.Reuse content