The History of Poisoning as Murder

THERE IS A REASON poison has always been called "the coward's weapon" and "the weapon of women." It requires no physical strength. It leaves no visible wound. Done correctly, it looks like illness, like bad luck, like an act of God rather than a human hand. For most of history, it was nearly undetectable. Thousands of people were murdered by poison and their killers never faced any consequences, because no one could prove the death was not natural. The history of poisoning is also, inevitably, the history of how societies learned to detect it.

The Ancient World's Pharmacopoeia of Death

The ancient world had access to an impressive range of lethal substances and was not shy about using them. Arsenic, extracted from naturally occurring minerals, was available throughout the ancient Mediterranean and Near East. It was flavorless, odorless in small quantities, and produced symptoms that resembled cholera or severe gastroenteritis. A small dose over time produced a slow wasting death that looked like natural illness. A large dose killed quickly, but could be attributed to spoiled food or disease. For a would-be poisoner with access to the right minerals, it was nearly perfect.

Ancient Greek sources describe the use of hemlock, the substance that killed Socrates in 399 BC. Hemlock contains the alkaloid coniine, which causes progressive ascending paralysis. Socrates reportedly died calmly, reporting the sensation of numbness moving up from his feet. Modern pharmacologists note that this is an accurate clinical description of hemlock poisoning. Whoever wrote the account either witnessed it or had reliable information. The Athenian state executed criminals with hemlock as a supposedly humane method, which tells you something about ancient views of what constituted mercy.

In ancient Rome, poison was so commonly used in political and family disputes that it became a cultural preoccupation. The first Roman law specifically addressing poisoning dates to 81 BC, the Lex Cornelia de sicariis et veneficis, which covered both assassins with weapons and poisoners. Its existence suggests the problem was significant enough to require legislation. Roman historians describe poisoning throughout the imperial period with a matter-of-factness that suggests contemporary readers would have found it familiar.

Locusta of Rome

The most famous professional poisoner of the ancient world was a Gallic woman named Locusta, employed by the empress Agrippina the Younger and later by the emperor Nero. According to the historian Tacitus, Agrippina used Locusta to poison the emperor Claudius in 54 AD, inserting the poison into a dish of mushrooms. Claudius died that night. His death allowed his stepson Nero to succeed him.

Nero subsequently used Locusta to poison his half-brother Britannicus, the biological son of Claudius, who might otherwise have challenged his rule. The first attempt reportedly failed; the dose was too mild and Britannicus merely had diarrhea. Nero had Locusta tortured and demanded a faster-acting poison. The second attempt succeeded at a dinner party, with Britannicus dying in convulsions before the assembled guests. Nero reportedly told the other diners that Britannicus suffered from epilepsy.

Locusta ran what appears to have been a poison school and professional practice, training others in her methods. She was eventually executed after Nero's death when the new emperor Galba came to power. She had served the imperial court through multiple reigns and multiple murders. Her career suggests that professional poisoners who were useful to the powerful could operate with effective impunity for as long as their patrons needed them.

The Borgias and Renaissance Italy

Renaissance Italy produced the most culturally elaborated tradition of political poisoning in European history, and no family is more associated with it than the Borgias. Rodrigo Borgia, who became Pope Alexander VI in 1492, and his son Cesare Borgia were accused by contemporaries of poisoning rivals with a white powder that some sources called "cantarella." Whether this was arsenic, a mixture of arsenic and phosphorus, or something else entirely is unclear. Some historians argue that the Borgia poisoning reputation was substantially exaggerated by political enemies. Others point to the suspicious pattern of deaths among their opponents.

What is clear is that the Borgias understood power and the removal of obstacles to it. Whether poison was their primary tool or their reputation simply made it a convenient explanation for inconvenient deaths, the cultural moment they inhabited was one in which poisoning was considered a real and constant danger for anyone in proximity to political rivals. Wealthy Italians had their food tasted before eating. They distrusted gifts of wine. They examined anything that came from enemies.

This cultural anxiety produced its opposite: a market for antidotes and protections. Bezoar stones, calcified masses from the stomachs of certain animals, were believed to neutralize poison and were extremely valuable. Unicorn horn, actually narwhal tusk, commanded enormous prices as a supposed poison detector. Cups made from various materials were claimed to change color or shatter when they came in contact with poisoned liquid. Almost none of these worked. They were sold to people who were genuinely frightened and could not afford to rely on nothing.

Arsenic: The Inheritance Powder

By the 17th and 18th centuries, arsenic trioxide had acquired the nickname "inheritance powder" in France, reflecting the perception that it was the primary tool of heirs impatient for their benefactors to die. It was widely available, sold as rat poison at apothecaries across Europe. It was cheap. It required no skill to administer. And it remained nearly undetectable until the 19th century.

The most significant poisoning scandal in French history, the Affair of the Poisons in the 1670s and 1680s, revealed a network of fortune tellers, alchemists, and poison sellers operating in Paris with clients that included members of the French aristocracy and possibly women in the circle of King Louis XIV himself. Investigations by a special commission, the Chambre Ardente, resulted in hundreds of arrests and at least 36 executions. The investigation was eventually shut down by Louis XIV when it began moving too close to his own court, a decision that left many cases unresolved.

The Italian woman Catherine Deshayes, known as "La Voisin," was burned at the stake in 1680. She had supplied poison, performed black masses, and provided a remarkable range of criminal services to her aristocratic clients. Her interrogations under torture implicated enough important people that the complete transcripts were sealed by royal order and not opened for decades.

The Science That Changed Everything

The era of undetectable arsenic poisoning ended in 1836 with the development of the Marsh test by British chemist James Marsh. The test could detect arsenic in biological tissue with high sensitivity, converting any arsenic present into arsine gas, which then produced a characteristic metallic deposit on a glass surface. For the first time, a medical examiner could look at a corpse and prove, chemically, that arsenic was present in amounts inconsistent with natural occurrence.

The first major trial to use Marsh test evidence was the 1840 case of Marie Lafarge in France, a young aristocrat accused of poisoning her husband Charles. The case became a sensation. Opposing expert witnesses argued about the test's reliability. The defense claimed the arsenic found in the body came from natural environmental sources. In the end, Lafarge was convicted on a combination of the chemical evidence and witness testimony about her purchase of arsenic. She maintained her innocence until she died in 1852.

The Marsh test and its successors changed not only forensic science but also poisoning itself. As detection became possible, the amateur poisoner who reached for arsenic faced real risk of discovery. Professional poisoners, if any still operated at scale, needed to become more sophisticated. The cat-and-mouse game between toxicology and poisoning has continued ever since, each advance in detection prompting either a shift to less detectable substances or simply a reduction in poisoning as a practical murder method.

Modern Poisonings

Political poisoning did not end with the Borgias or even with the 19th century. The 20th and 21st centuries produced a series of high-profile cases that demonstrate the method remains attractive to states and individuals who want a death that looks like illness or that carries a message without a visible weapon.

Alexander Litvinenko, a former Russian intelligence officer, was killed in London in 2006 with polonium-210, a radioactive isotope that requires a nuclear facility to produce. The method was not chosen for subtlety but for message: whoever killed him had access to state-level resources. Sergei Skripal and his daughter Yulia survived a 2018 poisoning in Salisbury with Novichok, a Soviet-era nerve agent. A British woman who came into contact with the discarded perfume bottle containing the agent died. Again, the choice of weapon was a statement about capability as much as an attempt at concealment.

Poison has tracked human history from the mushrooms in Claudius's dinner to the polonium in Litvinenko's tea. It has been the weapon of the powerful and the desperate, of states and individuals, of the patient and the impulsive. What has changed is not the weapon but the science arrayed against it. The body keeps its secrets less well than it once did. But the impulse to reach for something that kills without visible force has not changed at all.