Antoinette Scieri was born in Italy in 1890 and immigrated to France at a young age. During World War I, she served as a nurse at a clearing station in Doullens, where she was arrested in 1915 for stealing from wounded soldiers and impersonating them to receive funds. After her release in 1916, she married a man named Salmon and had two children. The marriage ended, and she later entered into a common-law relationship with Joseph Rossignol, with whom she had another child. In 1920, they settled in Saint-Gilles, France, where she offered her services as a private nurse.

Between 1924 and 1926, Scieri poisoned several of her elderly patients using the herbicide pyralion. The exact number of victims is uncertain, with sources citing between six and twelve or more. Her victims included her partner, Joseph Rossignol. 

Despite the increasing number of sudden deaths, local doctors attributed them to natural causes, delaying suspicion. Authorities eventually noticed that all the deceased had been under Scieri's care, leading to her arrest. She confessed to the murders, and on April 27, 1926, she was sentenced to death. However, her sentence was later commuted to life imprisonment. ​