If there is reason to believe that a murder or attempted murder may have been committed using poison, a forensic toxicologist is often engaged to examine pieces of evidence such as corpses and food items for poison content. In Orfila's time the primary type of poison in use was arsenic, but there were not any reliable ways of testing for its presence. Orfila created new techniques, refined existing techniques and described them in his first treatise, Traité des poisons (1813), greatly enhancing their accuracy.

In 1840, Marie Lafarge was tried for the murder of her husband. Although she had had access to arsenic, and arsenic had been found in the victim's food, none could be found in the corpse. Orfila was asked by the court to investigate. He discovered that the test used, the Marsh test, had been performed incorrectly, and that there was in fact arsenic in the body; LaFarge was subsequently found guilty.

General

• Forensic Toxicology, how it solves cases and the major cases it solved
• Bibliothèque Interuniversitaire de Médecine de Paris: Books, biography and studies on Orfila
•   This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Orfila, Mathieu Joseph Bonaventure". Encyclopædia Britannica (11th ed.). Cambridge University Press.