LIFE, the most precious commodity known to man, to be lived to the full, enjoyed to the maximum. It's so simple, so basic and the laws protecting it are so clear. The statute book says no one has the right to take another person's life and our legal system is set up to provide the most harsh punishments for those who kill.

The sixth Commandment written clearly in the Holy Bible states it unequivocally - 'Thou Shall Not Kill'. And, in times of peace, it's an easy enough code to follow.

But what happens when life isn't so sweet, when disease and disability makes life intolerable. Then the law seems harsh, inflexible, inhumane.

Forty-two-year-old Diane Pretty knows that law only too well. It's stopping her ending her life, because, being struck down with motor neurone disease, she physically won't be able to end it herself when the time comes. She will have to rely on her husband Brian. But if he helps her, then he will be in breach of the 1961 Suicide Act, laying himself open to prosecution. Her High Court bid, launched yesterday, is to win the right to die when she chooses, and lift any threat of her husband being brought to task for aiding and abetting a suicide.

The Luton mother-of-two was diagnosed with MND in 1999 and, in her case, the disease has been virulent, leaving her body wracked and unable to perform the most simple of tasks.

Under English law she is unable to die when she chooses, but under European law she may be able to change that. Her landmark case will cite Article 3 of the Human Rights Act, which protects against inhuman and degrading treatment. It will also cite Article 8 of the Act, which guarantees respect for one's private and family life. It's her life, it's her choice, it's her legal battle. She doesn't want to suffer, she doesn't want to become an object of pity or contempt.

But there are those in the medical profession who would not agree. Dr David Oliver, consultant in palliative care at Wisdom Hospice in Kent, says the case could lead to other terminally-ill people feeling a "duty" to end their lives. "It's very important to remember what happens with motor neurone disease," he says.

'There is a lot of fear about the disease and many people fear death from motor neurone disease, but I think increasing research has shown that death can be peaceful and is normally peaceful with good palliative care and that those fears are not necessary. There's also the fear over what happens to other people, that in the future people may feel they should be asking for suicide.

"People who have motor neurone disease or other terminal diseases may be feeling that they are a burden, and would be asking and feeling the duty to end their lives prematurely."

Critics also say a voluntary system of euthanasia could also be open to abuse, with mercy killings hiding sinister crimes.

But member of the Voluntary Euthanasia Society (VES), and retired neuro-surgeon at Newcastle General Hospital, Ram Kalbag believes the decision to live or die should rest with the individual.

"I love life, but I want to live until I die," the 75-year-old says. "I don't want my family to have to come and look at me. I want to die with dignity. I want to die when the times comes, without lingering."

In many ways the issue is a moot point. People suffering from terminal diseases are offered palliative care, the management of the symptoms, the pain, the discomfort, using powerful drugs - chemicals which are in themselves damaging to the human system. It's a fine line between killing the pain and killing the patient. They give the drugs to kill the pain not the patient, but there is the double effect," says Mr Kalbag. "Palliative care is the only speciality which doesn't have any failures."

He says the system operating in Holland provides all manner of checks and balances and the figures reflect this as it is seldom used. Only 2.4 per cent of deaths last year were attributed to voluntary euthanasia.

It's not a case of doctors being given a licence to kill and the physicians "putting patients down". The patient has to be diagnosed as being terminally ill and has to agree that nothing more can be done. This has to be verified by an independent doctor and then approved by a committee comprising members of the Dutch Medical Association and the Government.

"I would like to live as long as I can. I had a heart bypass 18 months ago and I don't say no to medicine - I am not a Luddite - but I also know what we can and cannot do," Mr Kalbag says.

"I am against suicide, it's morally wrong. But physician-assisted suicide is not killing them - they are dying anyway - it's just letting them go."

The Dutch case can be seen as part of a global trend, of the general public taking control of how they live and die. Belgium is considering similar legislation, while Spain is debating legislation on living wills, which are already legally binding in one of its provinces, Catalonia.

Doctor-assisted suicide has been legal in the American state of Oregon for four years now. The Health Division of the State of Oregon published a report into assisted deaths which showed that, in the year 2000, 27 terminally-ill adults died after taking lethal drugs which had been prescribed, at their explicit request, by their doctor.

The Oregon law has strict safeguards - qualifying adults must be terminally ill, mentally competent and make a number of requests. Two doctors must agree that their patient has less than six months to live and ensure that all alternative medical treatments have been explored.

Fears that the law would be abused proved to be unfounded. The same number of people received help as in 1999, and the total of 27 remains small in relation to the annual number of deaths in Oregon - 30,000.

In Britain, opinion polls consistently show that about 80 per cent of people support a change in the law.

Director of the VES, Deborah Annetts, says: "It should be every competent adult's human right to ask for and receive help in dying if they are incurably ill and are suffering unbearably. Just as high levels of public support have brought about legal change in the Netherlands, so too it is high time for the UK government to listen to public opinion."

A survey published in the Lancet demonstrated that non-voluntary euthanasia was more prevalent in countries which didn't allow voluntary euthanasia. It revealed that non-voluntary euthanasia, where a doctor ends a patient's life without receiving an explicit request from the patient, is four times more common in Belgium than it is in Holland.

Another survey, conducted in Australia in 1996, came to the conclusion that sensible legislation was essential for end-of-life decisions to be properly scrutinised, and in order to protect terminally-ill patients. Without legislation, patients were still helped to die by doctors, but decisions took place behind closed doors, and so were not regulated or fair.

While this country remains undecided, Mrs Pretty's suffering continues, even though she has made her decision, the hardest and most profound she has ever had to make in her life.