Benjamin Klein had quarreled with his mistress some time before he fell ill at the end of February 1803. Sophie Ursinus, the widow of a Berlin privy councillor, nursed him herself. She gave him an emetic, then a soup that left him worse. When she followed it with a dish of plums, Klein kept them back and had a chemist examine them in secret. They contained arsenic. The servant recovered, and his suspicion brought the Berlin authorities to three deaths that the city's doctors had signed off years earlier as natural.
She was born Sophie Charlotte Elisabeth Weingarten on May 5, 1760, in Glatz, in Silesia, the daughter of a secretary to the Austrian legation. After her father lost his post, she married, at nineteen, Theodor Ursinus, a much older counselor of the Prussian supreme court. The couple lived in Stendal until 1792 and then in Berlin. By her own statements to the magistrates it was a marriage of convenience: they considered themselves a legal couple and friends, she said, and neither pretended to more.
The man she did love, by her own account, was Rogay, a young Dutch officer. The affair may have had her husband's tacit consent. Rogay left Berlin for a time, came back, and died about three years before Theodor Ursinus, in 1797 by most accounts, of what his physicians called consumption. The inquiry of 1803 found that she had bought arsenic shortly before he died.
Theodor Ursinus died suddenly on September 11, 1800, the day after celebrating his birthday. On January 24, 1801, her aunt Christiane Witte died in Charlottenburg after a short illness and left her a large inheritance. Again, the investigators found, she had bought a large quantity of arsenic shortly beforehand.
The bodies were exhumed. Martin Heinrich Klaproth, one of the leading chemists in Prussia, and his assistant Valentin Rose examined the husband and could not confirm arsenic, though the condition of the organs and the convulsive contraction of the limbs left them suspicious. The aunt's remains were another matter; the examiners found she had been poisoned. Rose's work in the case showed the Prussian courts that a physician's bedside judgment of a natural death was not evidence enough, a lesson that fed the search for a reliable chemical test. The one that became standard, James Marsh's, came out in 1836.
According to one later account of Klein's statements to police, he gave the motives for all three deaths: she poisoned her husband because she did not want the burden of nursing an old man, Rogay because she feared he would leave her, and the aunt for her estate. He believed she had turned on him because he meant to quit her service and knew too much. None of this was tested as sworn testimony in the form it survives, and the court did not rest a conviction on it for the husband or the lover.
She disputed every point. The trial ended on September 12, 1803, with a conviction for the murder of Christiane Witte and the attempted murder of Klein, and a sentence of life imprisonment. The two deaths she was most suspected of, her husband's and her lover's, never resulted in a finding against her.
She served the sentence at Glatz, the town of her birth, and her confinement became known for its comfort. She kept her own furnishings, wore fine clothes and received guests, giving parties at which officers of the garrison were regular visitors. At some point she granted Klein a generous pension. She was pardoned in 1833, after thirty years, and returned to the upper-class society of Glatz. She died there on April 4, 1836, aged seventy-five.