Seven judges of the Supreme Court have begun hearing an appeal by Wicklow woman Marie Fleming against the refusal of the High Court to relax the absolute ban on assisted suicide.
In January the High Court ruled against the 59-year-old, who took a landmark case challenging the law on assisted suicide.
Ms Fleming, who has multiple sclerosis, wants an order declaring the ban on assisted suicide declared invalid under the Constitution and incompatible with the European Convention on Human Rights.
However the High Court said while her rights were affected by the ban, the legislation was not disproportionate.
While the court agreed personal autonomy, especially in medical matters, was a core Constitutional value affected by a ban on assisted suicide, it could not agree it was a disproportionate interference with this right.
Opening the case this morning senior counsel Brian Murray submitted the High Court decision was wrong.
He said the High Court had erred in a number of respects in terms of the proportionality test.
There was no credible evidence there would be an increase in the risk of unlawful deaths occurring if an exception was made in law for those in Ms Fleming's circumstances.
The High Court judgment appeared to assume the risk that others would break the law to be justification for subjecting Ms Fleming to a restriction and this was questionable, he said.
Mr Murray outlined Ms Fleming's condition to the court and said she was in constant pain and distress and suffered indignity.
She did not seek to have another person kill her but she wished to and could take the decisive physical step herself but needed assistance to do so.
She was unable to take a course of action open to an able-bodied person, he said.
He said the court would be asked to decide if the ban on assisted suicide impaired Ms Fleming's rights under the Constitution and the European Convention on Human Rights.
If so, he asked was it justified in doing so in the public interest and if it was proportionate.
The court would also be asked to decide if there was discrimination between Ms Fleming and an able-bodied person who can take their own life.
He said she has a right to a dignified death and to choose the manner and timing of that death.
Mr Murray said the cruel irony was, were she able-bodied and not experiencing the same acute degree of suffering, she would be able to do what she now wants to do.
While agreeing Ms Fleming's claim could be described as asserting a constitutional right to commit suicide, Mr Murray said that was not a description that does full justice to her claim.
The exercise of a right to kill oneself gives exercise to the right of a person to determine the course of their own lives, including a right to decide the time and manner in which it will end, he said.
He said the question was not to live or die, the question was dealing with a death which is inexorably pending.
The appeal is expected to last three days.
Assisted suicide ban appeal before the Supreme Court