THE POISON GAME
Until the early nineteenth century few tools existed to detect a toxic substance in a corpse. Sometimes investigators deduced poison from the violent sickness that preceded death, or built a case by feeding animals a victim's last meal, but more often than not poisoners walked free. As a result murder by poison flourished. It became so common in eliminating perceived difficulties, such as a wealthy parent who stayed alive too long, that the French nicknamed the metallic element arsenic poudre de succession, the inheritance powder.
The chemical revolution of the 1800s changed the relative ease of such killings. Scientists learned to isolate and identify the basic elements and the chemical compounds that define life on Earth, gradually building a catalog, The Periodic Table of the Elements. In 1804, the elements palladium, cerium, iridium, osmium, and rhodium were discovered; potassium and sodium were isolated in 1807; barium, calcium, magnesium, and strontium in 1808; chlorine in 1810. Once researchers understood individual elements they went on to study them in combination, examining how elements bonded to create exotic compounds and familiar substances, such as the sodiumchlorine combination that creates basic table salt (NaCl).
The pioneering scientists who worked in elemental chemistry weren't thinking about poisons in particular. But others were. In 1814, in the midst of this blaze of discovery, the Spanish chemist Mathieu Orfila published a treatise on poisons and their detection, the first book of its kind. Orfila suspected that metallic poisons like arsenic might be the easiest to detect in the body's tissues and pushed his research in that direction. By the late 1830s the first test for isolating arsenic had been developed. Within a decade more reliable tests had been devised and were being used successfully in criminal prosecutions.
But the very science that made it possible to identify the old poisons, like arsenic, also made available a lethal array of new ones. Morphine was isolated in 1804, the same year that palladium was discovered. In 1819 strychnine was extracted from the seeds of the Asian vomit button tree (Strychnos nux vomica). The lethal compound coniine was isolated from hemlock the same year. Chemists neatly extracted nicotine from tobacco leaves in 1828. Aconitine— described by one toxicologist as "in its pure state, perhaps the most potent poison known"— was found in the beautifully flowering monkshood plant in 1832.
And although researchers had learned to isolate these alkaloids— organic (carbon-based) compounds with some nitrogen mixed in— they had no idea how to find such poisons in human tissue. Orfila himself, conducting one failed attempt after another, worried that it was an impossible task. One exasperated French prosecutor, during a mid-nineteenth-century trial involving a morphine murder, exclaimed: "Henceforth let us tell would be poisoners; do not use metallic poisons for they leave traces. Use plant poisons… Fear nothing; your crime will go unpunished. There is no corpus delecti [physical evidence] for it cannot be found."
So began a deadly cat and mouse game—scientists and poisoners as intellectual adversaries. A gun may be fired in a flash of anger, a rock carelessly hurled, a shovel swung in sudden fury, but a homicidal poisoning requires a calculating intelligence. Unsurprisingly, then, when metallic poisons, such as arsenic, became detectable in bodies, informed killers turned away from them. A survey of poison prosecutions in Britain found that, by the mid-nineteenth century, arsenic killings were decreasing. The trickier plant alkaloids were by then more popular among murderers.
In response, scientists increased their efforts to capture alkaloids in human tissue. Finally, in 1860, a reclusive and single-minded French chemist, Jean Servais Stas, figured out how to isolate nicotine, an alkaloid of the tobacco plant, from a corpse. Other plant poisons soon became more accessible and chemists were able to offer new assistance to criminal investigations. The field of toxicology was becoming something to be reckoned with, especially in Europe.
The knowledge, and the scientific determination, spread across the Atlantic to the United States. The 1896 book Medical Jurisprudence, Forensic Medicine and Toxicology, cowritten by a New York research chemist and a law professor, documented the still-fierce competition between scientists and killers. In one remarkable case in New York, a physician had killed his wife with morphine and then put belladonna drops into her eyes to counter the telltale contraction of her pupils. He was convicted only after Columbia University chemist Rudolph Witthaus, one of the authors of the 1896 text, demonstrated the process to the jury by killing a cat in the courtroom using the same gruesome technique. There was as much showmanship as science, Witthaus admitted; toxicology remained a primitive field of research filled with "questions still unanswerable."