|Encyclopaedia Britannica 11th Edition||Public Domain via Project Gutenberg|
Marquise de (c. 1630-1676), French poisoner, daughter of Dreux d'Aubray, civil lieutenant of Paris, was born in Paris about 1630. In 1651 she married the marquis de Brinvilliers, then serving in the regiment of Normandy. Contemporary evidence describes the marquise at this time as a pretty and much-courted little woman, with a fascinating air of childlike innocence. In 1659 her husband introduced her to his friend Godin de Sainte-Croix, a handsome young cavalry officer of extravagant tastes and bad reputation, whose mistress she became. Their relations soon created a public scandal, and as the marquis de Brinvilliers, who had left France to avoid his creditors, made no effort to terminate them, M. d'Aubray secured the arrest of Sainte-Croix on a lettre de cachet. For a year Sainte-Croix remained a prisoner in the Bastille, where he is popularly supposed to have acquired a knowledge of poisons from his fellow-prisoner, the Italian poisoner Exili. When he left the Bastille, he plotted with his willing mistress his revenge upon her father. She cheerfully undertook to experiment with the poisons which Sainte-Croix, possibly with the help of a chemist, Christopher Glaser, prepared, and found subjects ready to hand in the poor who sought her charity, and the sick whom she visited in the hospitals. Meanwhile Sainte-Croix, completely ruined financially, enlarged his original idea, and determined that not only M. Dreux d'Aubray but also the latter's two sons and other daughter should be poisoned, so that the marquise de Brinvilliers and himself might come into possession of the large family fortune. In February 1666, satisfied with the efficiency of Sainte-Croix's preparations and with the ease with which they could be administered without detection, the marquise poisoned her father, and in 1670, with the connivance of their valet La Chaussée, her two brothers. A post-mortem examination suggested the real cause of death, but no suspicion was directed to the murderers. Before any attempt could be made on the life of Mlle Théresè d'Aubray, Sainte-Croix suddenly died. As he left no heirs the police were called in, and discovered among his belongings documents seriously incriminating the marquise and La Chaussée. The latter was arrested, tortured into a complete confession, and broken alive on the wheel (1673), but the marquise escaped, taking refuge first probably in England, then in Germany, and finally in a convent at Liége, whence she was decoyed by a police emissary disguised as a priest. A full account of her life and crimes was found among her papers. Her attempt to commit suicide was frustrated, and she was taken to Paris, where she was beheaded and her body burned on the 16th of July 1676.
See G. Roullier, La Marquise de Brinvilliers (Paris, 1883); Toiseleur, Trois énigmes historiques (Paris, 1882).