Greffier
On 10 June 1803, after the murder of Lord Kilwarden, O'Grady became Attorney-General and was sworn of the Privy Council of Ireland. He was one of the prosecuting counsel at the trial of Robert Emmet. In October 1805 he was made Lord Chief Baron, in succession to Lord Avonmore. He was a sound judge, and David Richard Pigot, his successor as Chief Baron of the Irish Exchequer, expressed the opinion: "O'Grady was the ablest man whose mind I ever saw at work". His witticisms on and off the bench were long remembered. O'Grady was one of the first to suspect the duplicity of the notorious informer Leonard McNally. He clashed with his superiors in 1816 when they brought quo warranto proceedings to challenge his right to appoint his son Waller as a Court clerk.