In the glittering court of Louis XIV's France, where opulence and intrigue walked hand in hand, one woman built a criminal empire that would

Episode 2 of 6 | Season 36: Serial Killers in History

Catherine Monvoisin's poisoning network spreads through the French aristocracy as her connections to the royal court deepen, implicating some of the most powerful figures in France.

Catherine Monvoisin began as Catherine Dyer, born in 1640 to a humble family on the outskirts of Paris. With little formal education but a natural aptitude for herbalism and folk medicine, she married Antoine Monvoisin, a jeweler whose business fell into ruin. As debt mounted, Catherine discovered she possessed something far more valuable than her husband's failing trade: an understanding of human desperation. She started as a fortune teller and midwife in the Villeneuve quarter, offering hope to clients who would pay handsomely for glimpses into their futures. Her charisma and discretion quickly attracted wealthy Parisians seeking solutions to problems they couldn't solve through conventional means. What made Catherine memorable wasn't just her accuracy in predictions—it was her willingness to provide tangible solutions, no matter how dark, to her clients' most desperate desires.

The case of La Voisin represents a watershed moment in French criminal history, marking the last great witch trial in France and fundamentally transforming the justice system. Her criminal enterprise exposed the intersection of superstition, organized crime, and aristocratic corruption at the highest levels of French society. The scandal, known as the Affair of the Poisons, forced Louis XIV to establish the Chambre Ardente, a special court that would try 442 suspects over three years and sentence 36 people to death. The case revealed how deeply rooted corruption had become within French aristocratic circles and led to lasting reforms in law enforcement, including increased surveillance of fortune tellers and new regulations controlling dangerous substances. Perhaps most significantly, La Voisin's trial marked the beginning of France's transition from superstition-based justice to rational investigation, helping usher the nation toward the Age of Enlightenment.

Catherine's transformation from fortune teller to serial poisoner was gradual but calculated. By the late 1670s, she had built a sophisticated criminal network operating from her lavish establishment in Paris. Her home featured elegant furnishings and private consultation rooms where nobles could discreetly arrange everything from love potions to murder. She employed astrologers, alchemists, and renegade priests, each contributing specialized skills to her expanding enterprise. Her most notorious services were the black masses—elaborate ceremonies combining Catholic ritual with occult practices, performed in secret locations outside Paris. These theatrical events attracted powerful clients who believed they could achieve anything from romantic conquest to political advancement through supernatural means. Among her most influential clients was Madame de Montespan, the official mistress of King Louis XIV himself. Their partnership began in 1667 when Montespan, fearing her waning influence over the King, sought Catherine's services. The rituals performed for Montespan were particularly blasphemous, involving twisted versions of Catholic mass performed over her body as a human altar, with claims that infant sacrifices occurred during these ceremonies.

La Voisin's criminal empire finally collapsed in 1679 when one of her associates was arrested for poisoning. Under interrogation, this associate revealed the extent of Catherine's network, leading to her arrest in March 1679. King Louis XIV established the Chambre Ardente specifically to prosecute poisoning cases emerging from this scandal. During her trial, Catherine showed neither remorse nor hesitation in describing her crimes, frankly stating that she provided services people desperately wanted. She implicated numerous prominent figures in French society, shocking the court with detailed accounts of ceremonies involving desecrated communion hosts and murder. The proceedings became so scandalous that Louis XIV ordered certain testimonies sealed, particularly those involving Madame de Montespan. On February 22, 1680, Catherine Monvoisin was executed at the Place de Grève in Paris before thousands of spectators. She remained defiant to the end, refusing last rites and cursing the priest who attempted to offer spiritual comfort. As flames engulfed her, witnesses reported she died without uttering a single cry of pain, maintaining her characteristic composure even in death.

This case draws from extensive historical sources documenting one of French history's most sensational trials. Court records from the Chambre Ardente provide detailed testimony transcripts, while contemporary accounts from French newspapers chronicle public reaction to the scandal. Seventeenth-century France's relationship with poison and witchcraft was complex—arsenic and other deadly substances were readily available from apothecaries with minimal regulation, making Catherine's trade frighteningly accessible. The aristocracy's willingness to engage with fortune tellers and participate in blasphemous ceremonies reveals the tension between Catholic orthodoxy and persistent folk beliefs in French society. Modern historians like Anne Somerset have extensively documented the Affair of the Poisons, providing crucial context for understanding how these crimes were perceived by contemporary society. The scandal permanently altered Louis XIV's relationship with his court, making him increasingly reclusive and preferring the controlled environment of Versailles over Paris's more unpredictable social circles.

Resources & Further Reading:

For those interested in learning more about the Affair of the Poisons and 17th century French criminal history:

• The Bibliothèque Nationale de France (National Library of France) houses original court documents from the Chambre Ardente trials
• "The Affair of the Poisons: Murder, Infanticide, and Satanism at the Court of Louis XIV" by Anne Somerset provides comprehensive analysis of the scandal
• The Musée de la Police in Paris maintains exhibits on famous French criminal cases including La Voisin
• The Archives Nationales (National Archives of France) preserve complete trial records and royal decrees related to the poisoning affair

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