When an elderly woman in Cologne died in the care of an outpatient nurse, her family found the blue folder in which she kept her savings empty. The nurse, Marianne Nölle, had been the only other person with a key to the flat. By one account it was the woman's daughters, and by another the son of Margarete E., eighty-nine, who went to the police and reported a theft. Prosecutors ordered an autopsy. The cause of death appeared to be pneumonia, but behind it lay poisoning with Truxal, a strong antipsychotic sedative that had never been prescribed to her.
Nölle was born in Cologne in 1938 and worked as a carer with an outpatient nursing service, looking after old and often frail people in their own homes. Several of them trusted her with their keys, power over their bank accounts and their papers. Over months, Cologne detectives exhumed bodies and found Truxal in them, found four packs of the drug in her flat and jewelry belonging to former patients, and watched her tangle herself in contradictions under questioning. By then, according to later reporting, she was planning to kill an eighty-five-year-old woman, Wilhelmine P., who had made her sole heir. The police came to believe she had killed seventeen people and tried to kill eighteen more.
On April 28, 1993, the Cologne regional court sentenced her to life imprisonment. The court found that she had poisoned her victims out of greed, with high doses of Truxal, sometimes mixed with diazepam, and then taken their money, jewelry and other valuables. With no confession, the conviction rested on the whole body of circumstantial evidence: her access, the unusually high concentrations of the drug, her possession of Truxal, the missing valuables and the recurring similarities between the cases. Accounts differ on the count: some give seven murders committed between 1984 and 1992, others, citing the judgment, six. The older cases could not be proved and several of the bodies had been cremated. The verdict became final in 1994, when the Federal Court of Justice rejected her appeal.
She denied the killings to the end and never confessed. She died on July 28, 2022, aged eighty-three or eighty-four.