The Butter Sandwich Killer

One of the most ruthless serial killers in German criminal history is Klaus O., better known as the Butter Sandwich Killer. This 57-year-old father of two poisoned the lunch sandwiches of his colleagues at the Ari valve manufacturing company in the town of Schloß Holte-Strukenbrock, North Rhine-Westphalia, with highly toxic substances from 2015 to 2018—not only to take pleasure in their suffering, but also to find out how the various poisons worked. Klaus O. had set up a laboratory in the basement of his house where he mixed the various poisons. The poison mixtures he concocted there were worse than the chemical weapons used in World War I. He packed them into paper envelopes and took them with him to work. Then he hid the poisonous paper bags in his file folder. When no one was in the break room, he tampered with his colleagues’ lunchboxes and sprinkled the powder on their sandwiches until he was caught on video in 2018. The company’s works council and management had arranged for the surveillance after 28-year-old Simon R. noticed that there were repeatedly crumbs on his lunch and that he had been vomiting constantly for some time. His coworker, 57-year-old Udo B., had also been suffering from severe cramps and stomach bleeding for some time. Furthermore, in 2016, 26-year-old student Nick N., who had been working at the plant during his semester break, was hospitalized for severe methylmercury poisoning, even though the plumbing company did not use mercury in its operations. He has been in a vegetative state ever since and will require long-term care for the rest of his life. Udo B. was also forced into early retirement due to his severe poisoning and must undergo dialysis for 6 hours three times a week. Simon R. continues to suffer from severe kidney damage to this day. No one had ever harbored even the slightest suspicion against Klaus O., who, although considered a loner, had performed his work conscientiously for nearly four decades and was always polite. Here, in fact, was a wolf in sheep’s clothing who abused his colleagues as guinea pigs for his experiments with toxic heavy metals. In March 2019, the Bielefeld Regional Court sentenced Klaus O. to life imprisonment followed by preventive detention. In July 2020, the Bielefeld Labor Court ordered Klaus O. to pay 1 million euros in compensation to the victims.