Locusta was said to have come from Gaul.[2]
Locusta served as a poisons expert under empress Agrippina the Younger. According to some historians, in AD 54, already notorious and imprisoned on poisoning charges, Locusta was ordered by Agrippina to supply a poison for the murder of her husband, Claudius. This was sprinkled on a mushroom and given to the emperor by his food-taster Halotus; There is a rumor that when the poison appeared to be ineffectual, the doctor Gaius Stertinius Xenophon murdered Claudius with a poisoned feather ostensibly put down his throat to induce vomiting, although it has yet been verified.[3]
She reportedly advised Agrippina to use Atropa belladonna as a poison. Extracts of atropa have been used for poisoning since antiquity, as the plant and its fruits contain tropane alkaloids (primarily hyoscyamine and scopolamine). Atropa-derived poisons were commonly used in ancient Roman murders, and previous empress Livia reportedly used them to murder her contemporaries. The effective doses of atropa needed to cause hallucinations for up to four days, and the ones needed to kill a person, were described by a 1st-century writer, Pedanius Dioscorides. Dioscorides called the plant "strychnos manikos" or "thryon."[4][5]
In AD 55, while still imprisoned, Locusta was called upon by Agrippina's son, the emperor Nero, to concoct a poison to murder Claudius' son Britannicus. When this poison was slow to work, Nero flogged Locusta with his own hand and threatened her with immediate execution, whereupon she supplied a quicker-acting poison that succeeded. Nero rewarded Locusta with a full pardon and large country estates, where he sent pupils to learn her craft.[6] Before Nero fled Rome in AD 68, he acquired poison from Locusta for his own use and kept it in a golden box. He eventually died by other means.[7]
After Nero's suicide, Locusta was condemned to die by the emperor Galba during his brief reign, which ended 15 January AD 69. Along with Nero's favorites Helius, Patrobius, Narcissus (freedman) and "others of the scum that had come to the surface in Nero's day," she was led in chains through the city and executed.[8]