The Supreme Court has begun hearing an appeal concerning the right to trial by a bilingual jury.
The High Court rejected a judicial review on the issue in 2010.
Peadar Ó Maicín from Rosmuc in Connemara, Co Galway, was charged with assault causing harm in Lettermore in Co Galway in 2008.
He has pleaded not guilty to the charge.
He wants to run and manage the case in Irish, and maintains that an integral part of this would be to have a jury which understands Irish.
He said that he would be disadvantaged if his case was heard with an interpreter.
Today's case concerns the clarification of these rights.