 He was admitted advocate on 20 December 1743, Appointed Sheriff of Perth in June 1754, in April 1766 he became solicitor for renewal of leases of the bishops' tithes, and solicitor and advocate to the commissioners for plantation of kirks in Scotland.Swinton was elevated to the Scottish bench, with the title of Lord Swinton, on 21 December 1782 replacing Alexander Lockhart, Lord Covington, and later, on the promotion of Lord Braxfield in 1788, was also made a lord of justiciary.At this time he had legal offices on Browns Square on the southern edge of Edinburgh.