Irene Leidolf

Maria Gruber, Irene Leidolf, Stephanija Meyer, and Waltraud Wagner made up one of the most unusual crime teams in 20th Century Europe. The four Austrian women were nurses working at Lainz General Hospital in Vienna, and together murdered scores of patients.

Wagner, 23, was the first to kill a patient with an overdose of morphine in 1983. She recruited Gruber, 19, and Leidolf, 21, and eventually the "house mother" of the group, 43-year-old Stephanija Mayer.

However, lethal injection didn't provide enough excitement, and soon the self-styled "death pavilion" had invented their own murder method: while one held the victim's head and pinched their nose, another would pour water into the victim's mouth until they drowned in their bed. Since elderly patients frequently had fluid in their lungs, it was an unprovable crime.

They were caught after they were overheard bragging about their latest murder at a local tavern. They confessed to 49 murders over six years, but may have been responsible for as many as 200.