Giulia Tofana

Giulia Tofana (also spelled Toffana, Tophana) (died in Rome, July 1659) was an Italian professional poisoner. She was famous for selling poison to women who wanted to murder their abusive husbands. She was the inventor of the famous poison Aqua Tofana, which is named after her.
Biography.
The information about her background is sparse. She was born in 1620 in Palermo, during a time when divorce was not a concept which existed. Sons and daughters were married off into loveless, abusive relationships with no possible way of escaping them, not until their spouse's death, nor unless one turns to prostitution and chooses to live with a reputation in shambles.
Giulia's home life was not entirely disclosed, however it can be inferred that she was indeed living with an abusive father; she was possibly the daughter of Thofania d'Adamo, who was executed in Palermo on 12 July 1633, accused of having murdered her husband Francis, Giulia's supposed father. She would have been 13 years old at the time of both her parents' murders. 
Giulia was described as very beautiful, and in light of her parents' deaths, she spent a lot of time with apothecaries, was present when they made their potions, and eventually developed her own poison, Aqua Tofana. It is, however, also possible that it was her mother, Thofania d'Adamo, who made the poison and passed the recipe on to her daughter. Regardless, she began to sell this poison to men and women who wanted to escape abusive spouses. Her daughter, Girolama Spera, was also active in this. She eventually moved her business to Naples and Rome.
Giulia's clientele was predominantly made up of women, and because she heavily sympathized with them, especially those of low-status, she gave the poison to women trapped in their unhealthy and dangerous marriages. Aqua Tofana was mostly disguised as either a healing oil, or an ordinary perfume. She became known as a friend to the troubled wife and received many referrals.
Giulia not only distributed the poison, but gave a walkthrough on how to use it, and what to do afterwards. Her poison was slow-acting as to make the death look like it was caused by a simple disease. She coached her clients to cry and exhibit emotion, and instructed them to demand for a coroner's exam, as to not draw any suspicion to them.
Tofana's business was finally revealed to the Papal authorities by a customer; however she was so popular that the locals protected her from apprehension. She escaped to a church, where she was granted sanctuary. When a rapid rumour, claiming that she had poisoned the water supply, tore through Rome, the police forced their way into the church and dragged Tofana in for questioning.
Death.
Under torture, she confessed to killing 600 men with her poisons in Rome alone between 1633 and 1651, but this cannot be confirmed owing to the torture and the widespread distribution of the poison. She was ultimately executed in Rome (in the Campo de' Fiori), together with her daughter (Girolama Spera, known as "Astrologa della Lungara") and three helpers, in July 1659. After her death, her body was thrown over the wall of the church that had provided her with sanctuary. Some of the users and purveyors were also arrested and executed, while other accomplices were bricked into the dungeons of the Palazzo Pucci.
Confusions.
There are incorrect references to her purported execution in Naples in 1719.
The legend that Wolfgang Amadeus Mozart might have been poisoned using Aqua Tofana is completely unsubstantiated.
Tofana is in many sources confused with Hieronyma Spara, "La Spara", a woman with a similar profession in Italy about the same time and with essentially the same name as Tofana's daughter Girolama Spera (Girolama is in Italian what Hieronyma is in Latin/Greek and note that in that time, the orthography of names was not solid, so Spera and Spara is probably the same).