The son of an Englishman and a Greek woman, Turnbull was educated in London, studied law in Philadelphia, and was admitted to the South Carolina Bar in 1794. An ardent nullifier, Turnbull wrote "Essays on the Usurpations of the Federal Government," many of which appeared in the Charleston Mercury under the pseudonym "Brutus." He gave numerous speeches and authored several pamphlets in defense of nullification.
Fraser, who supported the cause of the union, noted in his account book for 1832, "Era of Nullification," and that year was his least productive. The original Turnbull miniature must have been painted before his death in 1833; Fraser did three copies of it in 1835. Perhaps this is one of the copies, and as a result it is very severe. In addition, TurnbuIl's Greek heritage, the inclusion of diminutive spectacles, and his position on the nullification issue may have contributed to a somewhat harsh portrayal.