A Belfast-born barrister has became the second person to be appointed straight from the Bar to the Supreme Court.
Senior Counsel Donal O'Donnell was joined by family and colleagues in Dublin as he made his declaration in front of Chief Justice, Mr Justice John Murray.
The newly-appointed judge is a leading constitutional law practitioner and a law reform commissioner who has worked on a number of high-profile cases.
He represented the Government before the European Court of Human Rights and also appeared for the State during a separated mother-of-two's long-running legal battle to use frozen embryos against the wishes of her estranged husband.
Mr O'Donnell's wife Mary Rose Binchy attended the ceremony in Dublin's Four Courts along with his father, former Chief Justice of Northern Ireland Turlough O'Donnell.
The 51-year-old's brother, also named Turlough, is chairman of the Bar Council and works as a Senior Counsel in Dublin.
The newly-appointed judge was educated at University College Dublin, the Kings Inns and the University of Virginia.
He is also also a member of the Royal Irish Academy Committee on the Origins of the Irish Constitution.
Mr O'Donnell takes the seat left vacant by the appointment of Mr Justice Nicholas Kearns as President of the High Court.
The father-of-four follows in the footsteps of Adrian Hardiman, the first person to be nominated to the Supreme Court directly from the Bar and one of the youngest ever appointees.