Hahn was the youngest of 12 children. As a teenager she allegedly had an affair with a Viennese physician, though no records have been found of a Viennese doctor by the name she gave. They had a son named Oskar (also spelled “Oscar”). Her scandalized family sent her to America in 1929, while her son remained in Bavaria with her parents. While staying with relatives Max and Anna Doeschel in Cincinnati, she met fellow German immigrant Philip Hahn; they married in 1930. Anna Marie briefly returned to Germany to get Oscar, then the trio set upon life as a family.

Hahn allegedly began poisoning and robbing elderly men and women in Cincinnati’s German community to support her gambling habit. Ernst Kohler, who died on May 6, 1933, was believed to be her first victim. Hahn had befriended him shortly before his death; he left her a house in his will.  Her next alleged victim, Albert Parker, 72, also died soon after she began caring for him. Prior to Parker’s death, she signed an I.O.U. for $1,000 that she borrowed from him, but after his death the document was either discarded or simply “disappeared”. Jacob Wagner, 78, died on June 3, 1937, leaving $17,000 cash to his “beloved niece” Hahn. She soon began caring for 67-year-old George Gsellman, also of Cincinnati. For her service before his death on July 6, 1937 she received $15,000.

Georg Obendoerfer was the last to die, on August 1, 1937, after he traveled to Colorado Springs, Colorado with Hahn and her son. Police said that Obendoerfer, a cobbler, “died in agony just after Mrs. Hahn had bent over his deathbed inquiring his name, professing she did not know the man”. Her son testified at her trial that he, his mother, and Obendoerfer traveled to Colorado by train from Cincinnati together and that Obendoerfer began getting sick en route. An autopsy revealed high levels of arsenic in Obendoerfer’s body, which aroused police suspicions. Exhumations of two of her previous clients revealed that they had been poisoned.  Hahn was convicted after a sensational four-week trial in November 1937. Sentenced to death, she went to the electric chair at the Ohio Penitentiary in Columbus on December 7, 1938. She was buried in Mount Calvary Cemetery in Columbus.