A leader of the Real IRA who is serving a 20-year jail sentence for organising terrorist activities is to give evidence to the Smithwick Tribunal next Monday.
Michael McKevitt was convicted in the Special Criminal Court in 2003 of membership of the Real IRA.
Earlier this year, in the Belfast High Court he, along with Liam Campbell, was found liable of the Omagh bomb in which 28 people died.
Today Judge Peter Smithwick announced that the tribunal, which is investigating claims that gardaí colluded with the IRA in the murder of two RUC officers, will hear evidence from Mr McKevitt at what is normally the Special Criminal Court.
Meanwhile, a former Assistant Garda Commissioner has again failed to turn up at the tribunal to give evidence.
Kevin Carty sent in an unsigned medical certificate from a doctor in Austria.
Mr Carty was involved in an internal Garda investigation days after the murder of the two RUC officers in March 1989.
Earlier he had been criticised by Judge Smithwick after he failed to appear when he was called some months ago.
It then emerged he was working for the UN and was living in Armenia.
He agreed to return to give evidence to the Tribunal.
Return flights had been booked and paid for by the tribunal earlier this month.
Yesterday, however Mr Carty informed the tribunal by email that he would not be attending on medical advice.
Attached was an unsigned letter from a doctor in Vienna saying that as a result of a condition, Mr Carty should avoid stress and avoid two flights in 24 hours.
The doctor's certificate said Mr Carty lived in Poland.
Judge Smithwick said the issues raised by the unsigned certificate could have been resolved.
However, he was now in the position of considering whether he should refer the former Assistant Garda Commissioner to the High Court for his non-attendance.
The judge added that he hoped this would not happen and he would appear to give evidence.
