The High Court will rule today on a "right-to-die" legal challenge brought by a man with locked-in syndrome.
The 50-year-old, identified only as "AM" or "Martin", is questioning the legality of guidelines preventing doctors from assisting patients to commit suicide.
AM is almost totally paralysed by a stroke, unable to speak and wants to have the option of ending his life.
He is asking two judges in London to rule that the General Medical Council's (GMC) guidance on assisted suicide unreasonably prevents doctors from actively assisting patients whose "lives are in ruins" and want to die.
The GMC is opposing Martin's application for judicial review, arguing that it is an attempt to impose upon it "a positive obligation to tell doctors that they can, with impunity, conduct themselves in a manner which is, or might be, a breach of the criminal law".
The judges heard at a hearing in June that a previous attempt by Martin to commit suicide by stopping eating and drinking failed "in distressing circumstances".
He is now considering using the services of the Dignitas clinic in Zurich, which helps terminally ill patients end their own life.
In the last three years, about 30 UK residents have had an "accompanied suicide" at Dignitas.
The court was told that, in order to access Dignitas' services, Martin needs a doctor's medical report covering his medical history, including diagnosis, prognosis and treatment. But he cannot obtain the vital report because of the GMC guidance.
To consider other end-of-life options, Martin would also need medical advice.
The GMC guidance states that when patients raise the issue of assisted suicide, or ask for information that might encourage or assist them to end their lives, doctors should be prepared to listen and discuss the reasons - but must not actively "encourage or assist" as this would breach the Suicide Act 1961, and could lead to disciplinary proceedings.
Philip Havers QC, appearing for Martin, asked Lord Justice Elias and Mr Justice Collins to rule against the guidance.
Mr Havers argued the GMC should take the more "compassionate approach" of the Director of Public Prosecutions (DPP).
While assistance with suicide was still formally unlawful, the DPP policy meant that people providing assistance were prosecuted only exceptionally, he argued.
The Crown Prosecution Service website revealed that, of 110 cases referred to it between April 2009-April 2014 and recorded as assisted suicide or euthanasia, only one had been successfully prosecuted in October 2013.
Mr Havers told the judges: "We say the DPP's policy is the starting point and the GMC has failed to explain why it needs to take a different approach in order to protect the public.
"Therefore there is no inherent basis upon which the GMC can take a different approach."
He argued the courts, DPP and the public all took "a compassionate approach to those whose lives are in ruins from intractable suffering or terminal illness, who wish to end their lives and who need help from others to do so."
But people like Martin - once an active man but now living in a nursing home and dependent on others for every aspect of his life - were running into difficulties in seeking to end their "distressing and intolerable" lives because they could not get the help of a doctor.
Jenni Richards QC, for the GMC, urged the judges to dismiss Martin's legal challenge.
She said: "Doctors are expected to act within the law. That is a wholly unsurprising requirement."
If it was interfering with Martin's ability to obtain assistance from medical practitioners for his intended suicide "the solution lies in reform of the law", she said.