Served in company of gendarmes of Artois (1760-63). Went to St.-Domingue as a surveyor, where he sought a French military commission in vain (c. 1765). Commissioned engineer with the rank of captain in the American army, but soon returned to St.- Domingue. Concocted a scheme whereby the British might conquer Georgia (1778). Denounced by French authorities; defended himself by claiming that his plans were of no real use to the British and that this was merely a maneuver to mitigate the harshness of his treatment should he be captured at sea. Sent home and imprisoned (1779-83). Intermittently committed to mental asylums (1784-88). Eventually received a pension of 800 livres from the naval ministry.
Son of Dominique Saint-Pierre Dutailli. Younger brother of the famous writer Bernardin de Saint-Pierre.