Legal action brought by locked-in syndrome sufferer Tony Nicklinson, who wants a doctor to be able to end his "intolerable" life lawfully, can go ahead following a judge's ruling today.
The decision was announced at the High Court in London by Mr Justice Charles, who had been asked to decide on a preliminary "strike out" application in the case made by the Ministry of Justice.
He had heard argument that it was not for the courts to act, but Parliament.
Announcing his decision today the judge allowed most of Mr Nicklinson's case to proceed - striking out one part of his claim.
Mr Nicklinson, 57, who is married with two grown-up daughters and lives in Melksham, Wiltshire, wants a doctor to be "lawfully" able to end his life, which he sums up as "dull, miserable, demeaning, undignified and intolerable".
He launched a legal action seeking court declarations that a doctor could intervene to end his "indignity" and have a "common law defence of necessity" against any murder charge.
At a recent hearing, Paul Bowen, for Mr Nicklinson - who suffered a stroke in 2005 - said the Ministry of Justice had not advanced any arguments which were a sufficient "knock-out blow" to justify striking out the action.
His wife, Jane Nicklinson, says the only way to relieve his suffering is to kill him.
Mr Nicklinson, 57, who is married with two adult daughters and lives in Melksham, Wiltshire, wants a doctor to be able "lawfully" to end his life, which he sums up as "dull, miserable, demeaning, undignified and intolerable".
His wife, Jane Nicklinson, told BBC Radio 4's Today programme a stroke in 2005 left her husband able to communicate only by a voice-synthesiser that registers blinking.
"We are asking for it to be legal for someone to end his life. The only way to relieve Tony's suffering is to kill him. There's nothing else that can be done for him."
"He can't do anything. He's completely paralysed and he can't speak. If he has an itch I have to scratch it for him," she said.
Mr Nicklinson does not want to die immediately, she said. "He just wants to know when the time comes he has a way out. It's what he wants, and we are behind him.
"If you knew the kind of person he was before, life like this is unbearable for him. He realises as he gets older things are going to get worse."
"Twenty years ago Tony would have died. But people are being kept alive with such terrible conditions. Medical practice has become so much better but the law has not progressed with that.
She added: "He says now if he had know what life would be like for him now, he would have just laid down and died and would not have called for help."
But Baroness Finlay, a professor of palliative medicine at Cardiff University School of Medicine and a former president of the Royal Society of Medicine, said the law as it stands is "proportionate and clear" in granting patients the right to refuse treatment so that they might die.
She warned other patients could be left vulnerable if doctors are granted the right to kill patients.
"The difficulty is you set a precedent. If you change the law because one person wants something, who do you remove that protection from and put at risk? We have laws to protect the whole of the population.
"There are things that somebody might like to do, for example, for safety to carry a knife. But we say you are not allowed to because overall there is risk to the public."
She added: "I would dispute that the only way to relieve someone's suffering is to kill them."
Mr Justice Charles, sitting in London, has heard argument during the airing of a preliminary issue that it was not for the courts to act, but Parliament.
At a recent hearing Paul Bowen, for Mr Nicklinson said the Ministry of Justice had not advanced any arguments which were a sufficient "knock-out blow" to justify striking out of the action.
He said the Ministry of Justice submitted that "necessity can never afford a defence to a charge of murder".
But Mr Nicklinson argues that the MoJ "cannot establish on the balance of probabilities" that his case on necessity "has no real prospects of success".
Mr Bowen said Mr Nicklinson's case was that "an act of euthanasia or assisted suicide" was the only means "by which his suffering may be brought to an end and his fundamental common law rights of autonomy and dignity may be vindicated".
He told the judge that Mr Nicklinson's "invocation of the defence of necessity rests, in large part, upon the submission that the defence is necessary to allow his suffering to end and to give effect to his fundamental common law rights of autonomy and dignity".
Mr Nicklinson is seeking declarations that it is lawful for a doctor to terminate his life, with his consent and with him making the decision with full mental capacity.
Mr Bowen said the "courts have never considered directly the question arising in this case where voluntary active euthanasia is the issue".
At a previous hearing, David Perry QC, representing the Ministry of Justice, said Mr Nicklinson "is saying the court should positively authorise and permit as lawful the deliberate taking of his life".
He added: "That is not, and cannot be, the law of England and Wales unless Parliament were to say otherwise."
No matter how tragic the circumstances or situation, it was not a reason for "distorting the settled law".
It could only be Parliament "who could properly put into place a system with appropriate safeguards and conditions, not the courts taking this on a case-by-case basis".
But Mr Bowen said there was no bar to the courts dealing with such cases.
He told the judge: "The legislation of medically assisted dying is one area where there may be considerable advantages to a gradual, step-by-step development of the common law rather than the all or nothing approach of legislation."
Counsel added: "The court can extend the common law defence of necessity to the circumstances of the present case - an act of voluntary active euthanasia or assisted suicide of a competent adult - while stipulating that the application of the defence in other contexts will have to await the particular facts of a particular case.
"The court can lay down safeguards that must be observed if the doctor's actions are to be considered 'necessary and proportionate', including a requirement that in specified cases (or all cases) prior authorisation from a court will be necessary for that test to be satisfied."