Top judges are to rule on a challenge by a motor neurone disease sufferer against the law on assisted dying.
Retired college lecturer Noel Conway took his case to the Court of Appeal after he was refused permission to bring a judicial review over the blanket ban on providing a person with assistance to die.
Mr Conway, 67, from Shrewsbury, was diagnosed with the disease in November 2014 and is not expected to live beyond 12 months.
His lawyers say that when he has less than six months to live and retains the mental capacity to make the decision, "he would wish to be able to enlist assistance to bring about a peaceful and dignified death".
He wants a declaration that the Suicide Act 1961 is incompatible with Article 8, which relates to respect for private and family life, and Article 14, which protects from discrimination.
On Wednesday, Lord Justice McFarlane and Lord Justice Beatson will decide whether to give Mr Conway permission to appeal against the High Court's majority ruling that there was no arguable case to go to a full hearing.
The proceedings follow an action brought by Tony Nicklinson, who suffered from paralysis after a stroke.
That was ultimately dismissed in 2014 by the Supreme Court, which said it was important that Parliament debated the issues before any decision was made by the courts.
Mr Conway's case is different in that he has a terminal illness and his legal team are setting out a strict criteria and clear potential safeguards to protect vulnerable people from any abuse of the system.
In the High Court, Lord Justice Burnett said it remained "institutionally inappropriate" for a court to make a declaration of incompatibility.
Had Parliament done nothing after the Nicklinson case, Mr Conway's case for permission would be "unanswerable" however it might fare on further investigation.
But both the House of Commons and the House of Lords had debated the issue, with the result that Parliament had decided, at least for the moment, not to provide for legislative exceptions to the 1961 Act.