Lawyers for the State have told the Supreme Court it would be impossible to ensure proper safeguards against abuse if the law were to be changed to allow assisted suicide in certain cases.

The submission was made on day three of an appeal by Marie Fleming against a decision of the High Court which rejected her challenge to the ban on assisted suicide.

Senior Counsel for the State Shane Murphy said there was a wide range of concerns about the consequences of legalising assisted suicide.

Medical expert evidence on the issue had been deemed compelling in power and value by the High Court, he said.

That evidence suggested the risks to others were insurmountable as some might feel pressurised into opting to end their lives if the law was changed.

He said section 2.2 of the 1993 Criminal Law Suicide Act was an expression of social policy in regard to suicide and was a rational consideration.

The State was seeking to make a boundary line in maintaining the ban and was entitled to do so.

Earlier Michael Cush, also representing the State, said the decriminalisation of suicide did not create a constitutional right to take your own life.

Mr Cush said suicide was a severe social problem in Ireland with appalling consequences for families.

Statistics showed a sharp increase in 2011 and social policy remained adverse to it.

Asked by Mr Justice Adrian Hardiman if there was not a right to do that which is not forbidden, Mr Cush said even if there was a legal right there was certainly no Constitutional right to take your own life.

The judge said the social problem of suicide was very different to the case before the court and attitudes to both would be very different.

Mr Cush said there could not be a law preventing someone from aiding and abetting someone doing what was their right.

No such right existed, he said, adding that decriminalisation of the act of suicide did not create a right.

The primary concept of the Constitution was to protect life and any general right to take your own life would offend that, he said.

If there was no general right it was not open to the court to identify a particular class of persons not identified by the Constitution as enjoying such a right, he said.

There was not a single authority to support a general right, he said.

A previous case involving the withdrawal of medical treatment established a right to die a natural death but stopped there and went no further, he said.

It was either in the Constitution or not. The community and the common good had an interest in the right to life and establishing a general right to suicide would run counter to the State's interest in the right to life.

On the equality issue, he said the Oireachtas was entitled to have regard to the risk of involuntary death to other vulnerable people if the ban was to be relaxed.

That was a policy choice the Oireachtas was entitled to make, he said.

Ms Fleming, who has multiple sclerosis, is seeking an order declaring the ban on assisted suicide invalid under the Constitution and incompatible with the European Convention on Human Rights.

She claims she has the right to end her own life but because she is almost totally physically disabled she would need help to do so.

The criminal law prevents anyone giving that assistance and Ms Fleming claims this is a breach of her rights and discriminates against her as a disabled person.

The Human Rights Commission is supporting her case and has told the court it may be possible to craft a solution to take account of those in the particular circumstances of the terminally ill who wish to end their lives.

The appeal will continue next Tuesday.