He was born in Paris. He became an influential advocate in the parlement, and was prominent in opposition to the ministers Calonne and Loménie de Brienne.
Elected in 1789 to the states-general by the Paris nobility, he displayed remarkable eloquence. As a jurist, he contributed during the Constituent Assembly to the organization of the judiciary of France. In his report of March 29, 1790, he advocated trial by jury; but failed to introduce the jury system in civil cases.
Duport had formed with Barnave and Alexandre de Lameth a group known as the "triumvirate," which was popular at first. But after the flight of King Louis XVI to Varennes, Duport tried to defend him; as member of the commission charged to question the king, he found excuses, and on July 14 1791 he opposed the formal accusation. Having separated himself from the Jacobins, he joined the Feuillant party. After the Constituent Assembly, he became president of the criminal tribunal of Paris, but was arrested during the insurrection of 10 August, 1792. He escaped, probably with the complicity of Georges Danton, returned to France after the 9th of Thermidor of the year II, left it in exile again after the republican coup d'état of the 18th of Fructidor of the year V, and died at Appenzell in Switzerland in 1798.
See FA Aulard, Les Orateurs de la Constituante (2nd ed., Paris, 1905, 8vo).
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