Marie-Madeleine-Marguerite d'Aubray was born in Paris in 1630, daughter of a civil lieutenant of the city, and married the Marquis de Brinvilliers in 1651. She took as her lover an army officer, Godin de Sainte-Croix, and when her father had him imprisoned in the Bastille the affair turned into something else. Sainte-Croix is said to have learned about poisons while in prison.
Her father, Antoine Dreux d'Aubray, died in 1666 after months of worsening illness. Her two brothers died in 1670, both after the same slow decline. She inherited. The deaths were attributed to natural causes at the time, as arsenic poisoning routinely was.
The case broke when Sainte-Croix died suddenly in 1672 and a box of his papers was opened, containing letters from her and a quantity of poison. She fled to England and then to a convent at Liege, where an officer of the French crown, posing as a priest, persuaded her to leave sanctuary. She was arrested and brought back.
She was tried in 1676, convicted, subjected to the water torture, and on July 16 beheaded on the Place de Greve, her body burned afterwards. Madame de Sevigne, who watched the crowd, wrote about it, and it is largely through her letters that the scene is remembered.
The figure of fifty or more in this roster comes from a tradition that she tested her poisons on patients in the Hotel-Dieu, the Paris charity hospital, before using them on her family. It appears in eighteenth and nineteenth century accounts and there is no trial evidence for it. The convictions concern her father and her brothers. The hospital story should be read as what Paris said about her rather than as something established.
What the case did establish, in the minds of the authorities, was that poison could be bought in Paris. That belief produced the Chambre Ardente and, three years later, the arrest of Catherine Monvoisin.