McDermott attended University College Dublin and the King's Inns.
[1] He was counsel for the Morris Tribunal, which addressed allegations against the Garda Síochána.
He received €3.2 million in fees, which was the highest amount paid to any of the tribunal's lawyers.
[2] He is the author of legal texts on the Misuse of Drugs Act and the law of prisons in Ireland.
[9] He was the presiding judge in the trial surrounding the murder of Ana Kriégel.