Affair of the Poisons (1677–1682): Scandal at Louis XIV's Court

The Affair of the Poisons was a criminal scandal that shook the court of Louis XIV between 1677 and 1682. Police in Paris uncovered a network of fortune-tellers, poison sellers and renegade priests whose clients included members of the high nobility, and witnesses eventually accused the king’s mistress, Madame de Montespan. A special court sentenced 36 people to death before the king, alarmed at what it might reveal, brought the inquiry to a close.

Background: poison and fear in Paris

In the 17th century poison was widely feared. Arsenic was easy to buy, hard to detect, and its symptoms could be confused with natural illness. The fear grew in 1676 with the trial of the Marquise de Brinvilliers, a noblewoman who, with her lover Godin de Sainte-Croix, had poisoned her father and two of her brothers to gain their inheritance.

Sainte-Croix died in 1672, and papers found among his belongings exposed the crimes. Brinvilliers fled abroad but was arrested in Liège, brought back to Paris and executed on 17 July 1676. Her case convinced many that poisoning was common among the wealthy, and that other killers were still at large.

The man responsible for order in the capital was Gabriel Nicolas de La Reynie, appointed in 1667 as Paris’s first lieutenant general of police. He was a careful, determined investigator, and he would lead the inquiry that followed.

The investigation begins

In 1677 La Reynie’s officers began following leads about women who sold “inheritance powders”, as poisons were nicknamed. Early in 1679, according to the standard accounts, a fortune-teller named Marie Bosse boasted at a dinner that she would soon retire after a few more poisonings. An undercover informant arranged to buy poison from her, and she was arrested with her associates.

Bosse named others, and the trail led to the most prominent figure of all: Catherine Monvoisin, known as La Voisin. She ran a busy trade in palm-reading, love charms, abortions and, according to the prosecution, poison. La Voisin was arrested on 12 March 1679 as she left Mass.

The Chambre ardente

Louis XIV supported the inquiry. On 7 April 1679 he created a special commission to judge the cases, popularly called the Chambre ardente (“burning chamber”) after the black-draped, candle-lit rooms in which such courts had traditionally sat. It met at the Arsenal in Paris and worked in secret, which allowed La Reynie to pursue suspects of high rank.

The accused included famous names. Olympe Mancini, Countess of Soissons and niece of Cardinal Mazarin, fled to Brussels in January 1680 rather than face questioning. The Duchess of Bouillon appeared before the court and treated it with open contempt. The Marshal-Duke of Luxembourg, one of France’s leading generals, spent months in the Bastille before being cleared. The playwright Jean Racine was named by La Voisin in connection with the death of the actress Marquise Du Parc, but he was never charged.

La Voisin was convicted of witchcraft and poisoning and burned alive on the Place de Grève in Paris on 22 February 1680.

The accusations against Madame de Montespan

After her mother’s death, La Voisin’s daughter, Marie-Marguerite Montvoisin, made sensational statements in 1680. She claimed that Madame de Montespan, the king’s long-time mistress and mother of several of his children, had for years bought love powders to keep Louis’s affection. She also described black masses, sacrilegious rituals in which a priest, Abbé Étienne Guibourg, was said to have said Mass over the body of a woman, and alleged that Montespan had been involved in a plot against the king and against his young favourite, Mademoiselle de Fontanges.

Other prisoners, including Guibourg himself, made similar claims. Much of this testimony came from people facing death or torture, who had reasons to tell investigators what they thought would save them, and many details cannot be verified. Historians still disagree: some think Montespan probably did buy love charms, which was a common practice, while very few accept that she plotted to kill the king.

The king closes the case

The accusations put Louis XIV in an impossible position. A public trial of the mother of his children would have caused a scandal across Europe. In 1680 he ordered that the evidence concerning Montespan be kept apart and not presented to the court.

The Chambre ardente continued to judge other cases until it was dissolved in July 1682. Prisoners whose testimony touched Montespan were never tried; instead they were sent, by royal order (lettre de cachet), to remote fortresses, where they were held in isolation for the rest of their lives. Montespan stayed at court for some years but lost the king’s favour, and Madame de Maintenon rose in her place. She left court in 1691.

Louis later destroyed La Reynie’s secret files on the matter, burning them in 1709. Some of La Reynie’s notes and other records survived in the archives of the Bastille, which is how historians know as much as they do.

Key people

• Gabriel Nicolas de La Reynie (1625–1709): Lieutenant general of police in Paris and the chief investigator, who interrogated hundreds of suspects and kept detailed notes.
• Catherine Monvoisin, La Voisin (c. 1640–1680): Fortune-teller and seller of potions at the centre of the network, executed in 1680.
• Françoise-Athénaïs, Marquise de Montespan (1640–1707): Louis XIV’s mistress from the late 1660s, accused by witnesses but never charged. She spent her final years in religious devotion and charity.
• Abbé Étienne Guibourg: An elderly priest accused of performing black masses; he was imprisoned for life rather than tried.
• Louis XIV: The king, who first encouraged the inquiry and then limited it when it reached his own household. At the time he was spending more and more of his time at the château that would become the Palace of Versailles.

The fate of the prisoners held without trial shows the same secretive side of royal justice as the case of the Man in the Iron Mask, another prisoner kept for decades in a fortress by the king’s order, with his story hidden from the public.

By the numbers

Consequences

In July 1682 the king issued an edict that reshaped French law on these matters. The sale of arsenic and other poisons was restricted to apothecaries and other licensed professionals, who had to keep records of buyers. Fortune-telling and claims of magic were treated as fraud and sacrilege, and the edict largely abandoned the idea that witchcraft was a real crime, a step that historians see as a turning point in the decline of witch trials in France.

The affair also reinforced the authority of the Paris police and of La Reynie personally, showing how far a centralised police force could reach into the lives of the powerful.

Timeline

• 1676, 17 July: The Marquise de Brinvilliers is executed for poisoning.
• 1677: Paris police begin investigating poison sellers.
• 1679, early January: Marie Bosse is arrested.
• 1679, 12 March: La Voisin is arrested.
• 1679, 7 April: The Chambre ardente is created.
• 1680, January: The Countess of Soissons flees to Brussels.
• 1680, 22 February: La Voisin is burned at the Place de Grève.
• 1682, July: The Chambre ardente is dissolved and a new edict on poisons is issued.

Why it matters

The Affair of the Poisons revealed the hidden world beneath the splendour of Louis XIV’s court, where fear, ambition and superstition mixed with real crime. It showed both the reach and the limits of absolute monarchy: the king’s police could expose the powerful, but the king could also bury evidence to protect his own household. Its legal reforms helped end the prosecution of witchcraft in France.