Catherine Monvoisin, or Montvoisin, née Deshayes, known as "La Voisin" (c. 1640 – February 22, 1680), was a French fortune teller, poisoner and an alleged sorceress, one of the chief personages in the affaire des poisons, during the reign of Louis XIV.
Catherine Deshayes was married to Antoine Monvoisin, a jeweller with a shop at Pont-Marie in Paris. After her husband was ruined, La Voisin started her career by practising chiromancy and face-reading to support her family. She practiced medicine, especially midwifery, and performed abortions.
As for her practice in fortune telling, she was to say that she developed the talent God had given her. She was to have been taught the art of fortune telling at the age of nine, and after her husband became ruined, she decided to profit by it. She studied the modern methods of physiology and reading the client's future by reading their faces and hands. She also spend a lot of money to provide an atmosphere which could make the clients more inclined to believe in the prophecies. For example, she acquired a special robe of crimson red velvet embroidered with eagles in gold for a price of 1500 livres to perform in.
In 1665/66, her fortune telling was questioned by the priests of Saint Vincent de Paul's order, the Congregation of the Mission, but La Voisin defended herself successfully before the professors at the Sorbonne.
During her work as a fortune teller, she noticed the similarities between her customers wishes about their future: almost all wanted to have some one fall in love with them, that some one would die so that they might inherit, or that their spouses would die, so that they might marry some one else. Initially, she told her clients that their will would be true if it was also the will of God. Then, she started to recommend to her clients some action that would make their dreams come true. These actions were initially to visit the church of some particular saint; eventually, she started to sell amulets and recommend magical practices of various kinds. The bones of toads, teeth of moles, Spanish flies, iron filings, human blood and mummy, or the dust of human remains, were among the alleged ingredients of the love powders concocted by La Voisin.
Finally, she started to sell aphrodisiacs to those who wished for people to fall in love with them, and poison to those who wished for some one to die. Her knowledge of poisons was not apparently so thorough as that of less well-known sorcerers, or it would be difficult to account for Louise de La Vallière's immunity. The art of poisoning had become a regular science at the time, having been perfected, in part, by Giulia Tofana, a professional female poisoner in Italy, only a few decades before La Voisin.
She arranged black masses, where the clients could pray to the Devil to make their wishes come true. During at least some of these masses, a woman performed as an altar, upon which a bowl was placed: a baby was held above the bowl, and the blood from it was poured into the bowl. She had a large network of colleagues and assistants, among them Adam Lesage, who performed allegedly magical tasks; the priests Étienne Guibourg and abbé Mariotte, who officiated at the black masses; and poisoners like Catherine Trianon.
La Voisin had many clients among the aristocracy and made a fortune from her business. Among her noted clients were countess de Soissons, duchess de Bouillon; Comtesse de Gramont ("la belle Hamilton"), François-Henri de Montmorency, duc de Luxembourg, princesse Marie Louise Charlotte de Tingry, marchioness Benigne d'Alluye, countess Claude Marie du Roure, count de Clermont-Lodéve, countess Jacqueline de Polignac, duchess Antoinette de Vivonne, Marquis Louis de Cessac, Marquis Antoine de Feuquieres and Marechal de la Ferthe.
La Voisin resided at Villeneuve-sur-Gravois, where she received her clients. She tended to her clients all day, and entertained at parties with violin music in her gardens at night, attended by Parisian upper class society. The house also included a furnace for the bodies of dead babies, who were then buried in the garden. She regularly attended at the services at the church of the Jansenist abbé de Sant-Amour, principal at the Paris University, and godmother of her daughter was the noblewoman de la Roche-Guyon. She supported a family of six, including her mother, and among her lovers were the executioner Andre Guillaume, Latour, vicomte de Cousserans, count de Labatie, the alchemist Blessis, the architect Fauchet and the magician Adam Lesage. At one point, Adam Lesage tried to induce her to kill her husband, but she regretted the plan and aborted the process. La Voisin was interested in science and alchemy and financed several private projects and enterprises, some of them made by con artists who tried to fool money out of her. Privately, she suffered from alcoholism, was apparently abused by Latour, and engaged in severe conflicts with her rival, poisoner Marie Bosse.
Connection to Madame de Montespan 
The most important client of La Voisin was Madame de Montespan, official royal mistress to King Louis XIV of France. Their contact were often performed through the companion of Montespan, Claude de Vin des Œillets. In 1667, Montespan hired La Voisin to arrange a black mass. This mass was celebrated in a house in Rue de la Tannerie. Adam Lesage and abbé Mariotte officiated, while Montespan prayed to win the love of the king. The same year, Montespan became the official mistress of the king, and after this, she employed La Voisin whenever a problem occurred in her relationship with the king.
In 1673, when the king's interest in Montespan seemed to deteriorate, Montespan again employed La Voisin, who provided a series of black masses officiated by Etienne Guibourg. On a least one occasion, Montespan herself acted as the human altar during the mass. La Voisin also provided Montespan with aphrodisiac, with which Montespan drugged the King. During the king's affair with Soubise, Montespan used aphrodisiac provided by Voisin's colleague Francoise Filastre and made by Louis Galet in Normandy.
In 1677, Montespan made clear that if the king should abandon her, she would have him killed. When the King entered into a relationship with Angélique de Fontanges in 1679, Montespan called for La Voisin and asked her to have both the king and Fontages killed. La Voisin hesitated, but was eventually convinced to agree. At the house of her colleague, Catherine Trianon, La Voisin constructed a plan to kill the king together with the poisoners Trianon, Bertrand and Romani, the last being also the fiancé of her daughter. Trianon was unwilling to participate and tried to make her change her mind by constructing an ill-fated fortune for her, but Voisin refused to change her mind. The group decided to murder the king by poisoning a petition, to be delivered to his own hands.
The 5 March 1679, La Voisin visited the royal court in Saint-Germain to deliver the petition. At that day, however, there were too many petitioners and the king did not take them in his hands, which made her return without having delivered it. Upon her return to her home in Paris, she was castigated by a group of monks. She handed the petition to her daughter and asked her to burn it, which she also did. The next day, she made plans to visit Catherine Trianon after mass, to plan the next murder attempt upon Louis XIV.
Investigation and execution 
The death of the king's sister-in-law, the Duchesse d'Orléans, had been falsely attributed to poison, and the crimes of Madame de Brinvilliers (executed in 1676) and her accomplices were still fresh in the public mind. In parallel, a riot took place where people accused witches of abducting children for the black masses, and priests reported that a growing number of people were confessing to poisoning in their confessions.
In 1677, the fortune teller Magdelaine de La Grange was arrested for poisoning, and claimed that she had information about crimes of high importance. The arrest of the successful fortune teller and poisoner Marie Bosse and Marie Vigoreux in January 1679, made the police aware that there existed a network of fortune tellers in Paris who dealt with the distribution of poison.
The 12 March 1679, La Voisin was arrested outside Notre-Dame de Bonne-Nouvelle after having heard mass, just before her appointed meeting at Catherine Trianon. In April 1679, a commission appointed to inquire into the subject and to prosecute the offenders met for the first time. Its proceedings, including some suppressed in the official records, are preserved in the notes of one of the official court reporters, Gabriel Nicolas de la Reynie.
At the arrest of La Voisin, her maid Margot stated that the arrest would mean the end of a number of people of all positions of society. The arrest of La Voisin was followed by the arrest of her daughter Marguerite Monvoisin, Guibourg, Lesage, Bertrand, Romain and the rest of her network of her associates. La Voisin was imprisoned at Vincennes, were she was subjected to questioning. On 27 December 1679, Louis XIV issued an order that the whole network should be exterminated by all methods regardless of the rank, gender or age of those involved.
La Voisin confessed to the crimes she was accused of and described the development of her career. She was never subjected to torture: a formal order was issued giving permission to the use of torture, but it was made clear that the order was not to be put in effect, and consequently it was never made use of. The reason it suggested to be the fear that she might give away the names of influential people if she was questioned under torture. La Voisin never mentioned the names of any of her clients during the interviews. She once mentioned to the guards, that the question she feared most was that they should ask her about her visits at the royal court. It is likely that she was referring to Montespan as her client and her attempt of murdering the king, and that she feared that such a confession should result in her execution for regicide. Her list of clients, the arranging of the black masses, her connection to Montespan and the murder attempt on the king was not to be revealed until after her death, when it was stated by her daughter and confirmed by the uncontaminated testimonies of the other accused.
La Voisin was convicted of witchcraft and was burned in public on the Place de Grève in Paris the 22 February 1680. In July, her daughter Marguerite Monvoisin revealed her connection to Montespan, which was confirmed by the statements of the other accused. This caused the monarch to eventually close the investigation, seal the testimonies and place the remaining accused outside of the public justice system by imprisoning them under a lettre de cachet.
In fiction 
La Voisin and her organisation is portrayed in a novel by Judith Merkle Riley: The Oracle Glass (1994)
ボアザン, by Takatoo Rui, is a manga partially based on La Voisin.
See also 
- Marie-Josephte Corriveau, a Canadian woman convicted of murder in 1763, later acquiring a legend and comparison to La Voisin
- Giulia Tofana, another female poisoner, in Italy, only a decade before La Voisin
- Chisholm, Hugh, ed. (1911). "La Voisin". Encyclopædia Britannica (11th ed.). Cambridge University Press.
- Anne Somerset - The Affair of the Poisons: Murder, Infanticide, and Satanism at the Court of Louis XIV (St. Martin's Press (October 12, 2003) ISBN 0-312-33017-0)
- Excerpts from Bastille trial records of Guibourg and LaVoisin (French and English translation)
- Frantz Funck-Brentano: Princes and Poisoners Or Studies of the Court of Louis XIV
- H Noel Williams: Madame de Montespan and Louis XIV