McDermott frequently appeared on Irish television and radio as a commentator on legal matters. He often appeared on "Morning Ireland", "Today with Seán O'Rourke", "", and Newstalk on legal topics such as criminal and constitutional law. He received attention for his analysis and comments on the referendum to establish the Court of Appeal and the referendum to repeal the Eighth Amendment. In 2017, a murder trial at the Central Criminal Court was collapsed by the judge after the jury heard comments McDermott made describing the defence of provocation in an unrelated discussion on "Prime Time".