Agrippina the Younger
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 the empress Agrippina the Younger 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; when this poison appeared to be ineffectual, the doctor Gaius Stertinius Xenophon murdered Claudius with a poisoned feather ostensibly put down his throat to induce vomiting.