Hahn was born Anna Marie Filser in Bavaria in 1906 and emigrated to Cincinnati in 1929, settling in the city's large German-speaking community. She married, had a son, and lost heavily at the racetrack.
She advertised and asked around for positions as a housekeeper or nurse to elderly men, most of them German-born widowers in the Over-the-Rhine district. Between 1932 and 1937 five died: Ernest Koch, seventy-three; Albert Parker, seventy-two; Jacob Wagner, seventy-eight; George Gsellman, sixty-seven; and George Obendoerfer, sixty-seven. She gave them arsenic and, in one case, croton oil, and she took cash, forged cheques, altered a will and had property transferred to her. The deaths were recorded as natural, which for elderly men in the 1930s required no argument. The American press called her Arsenic Anna and the Blonde Borgia.
The case broke in 1937 when Obendoerfer died in Colorado, where she had taken him on a trip, and a doctor there found arsenic. The Cincinnati deaths were then examined and exhumations followed.
She was tried in Cincinnati in 1937 in a case that filled the papers nationally, convicted of Wagner's murder, and sentenced to death. She was electrocuted at the Ohio Penitentiary on December 7, 1938, the first woman to be executed in Ohio's electric chair.
She denied everything to the end and then, on the day of her execution, wrote a long confession which a newspaper had contracted to buy and published. That document is the source for most of the detail about the individual deaths, and it was written for money by a woman with hours to live.