[2][3] His father James Geoghegan was a judge of the Supreme Court.
At UCD, he was the auditor of the University College Dublin Law Society between 1960 and 1961.
[6] Geoghegan was called to the Bar in 1962, becoming a senior counsel in 1977, practising in Dublin and the Midland Circuit.
[4][6] He was also called to the bar in Northern Ireland and in England and Wales.
[10] He was elevated to the Supreme Court of Ireland in 2000, replacing Donal Barrington.