Lawyers for the Dáil's Public Accounts Committee (PAC) have begun outlining their arguments to the Supreme Court in the case being taken by the former CEO of the Rehab Group, Angela Kerins.
Ms Kerins is appealing against the High Court's dismissal of her action against the committee.
She claims that two hearings in 2014, into money paid to the Rehab Group, amounted to a witch hunt against her.
The High Court found the courts could not intervene at all in relation to Dáil committee proceedings.
In his submissions yesterday, Ms Kerins' Senior Counsel, John Rogers said his client's life had been changed forever at the first hearing on 27 February 2014.
She was so overwhelmed by how she had been treated that she later self harmed, he said.
Opening the State's arguments, Senior Counsel Paul Gallagher said he wanted to repeat the sincere sympathy of the committee members to Ms Kerins on her illness and the difficulties she experienced, although he said they did not accept responsibility for them.
Supreme Court judge, Ms Justice Elizabeth Dunne pointed out that this expression of sympathy had been absent completely from a document sworn on behalf of the committee replying to the document giving details of what had happened to Ms Kerins.
Mr Gallagher said this was a very important case, which raised fundamental constitutional issues.
He said the arguments raised by Ms Kerins' lawyers were not consistent with the constitution and would undermine freedom of speech in the houses of the Oireachtas - a core principle of our democracy.
Mr Gallagher said this freedom of speech was critical to the resolution of this case.
It was regarded as essential to the proper functioning of a democracy.
He said freedom of speech was only tested when someone alleged they had been harmed or offence had been caused.
But he said even if someone had been harmed by something said in the Oireachtas, this did not provide a legal basis for removing the protection for freedom of speech in the Oireachtas.
Mr Gallagher said Ms Kerins' case was based on an analysis of the utterances made by committee members and was asking the court to evaluate what they meant - that was an exercise the court could not engage in under the Constitution.
Mr Gallagher said remarks made by members of committees during the committee hearings were protected along with remarks made in the houses of the Oireachtas.
He said committees played a fundamental role in the parliamentary process, and the Oireachtas could not operate or discharge its constitutional obligations without the committee system.
Committees were involved in holding the Government to account and in representing voters.
The PAC dealt with issues of State expenditure, of very large sums of money, of whether the State was getting value for money and whether the rules applied to bodies getting payments from the State even if it was in the context of paying for services.
Mr Gallagher pointed out that Ms Kerins attended the committee hearing in February voluntarily and could have left the hearing at any time.
So he said, it was not necessary for the court to intervene to decide if the committee had been acting outside its powers.