His proposers were Robert Arbuthnot, Dugald Stewart and Alexander Fraser Tytler.
[2] Smythe was raised to the bench, in succession to Francis Garden of Gardenstone, on 15 November 1793, taking the title of Lord Methven.
He was appointed a commissioner of justiciary on the death of Lord Abercromby, 11 March 1796, resigning the post in 1804.
[3] He was taken ill suddenly while walking and died half an hour later[4] at his house at 28 St Andrew Square in Edinburgh on 30 January 1806.
By his second wife, Euphemia Amelia Murray of Lintrose, a noted singer,[5] daughter of Mungo Murray of Lintrose, who was reckoned a beauty of her time and was the subject of one of Robert Burns's songs, he had two sons and two daughters.