A psychologist by training, Mitchell translated theories about learned helplessness into operational practice, designing the "enhanced interrogation" program that the CIA applied to detainees in the years after September 11. The Senate Intelligence Committee's investigation later concluded the techniques produced no unique intelligence and that the program had been misrepresented to overseers. The $81 million contract his firm received made him among the most directly compensated architects of what critics and legal scholars have characterized as state-sanctioned torture.

Hahn operated within a narrow social world — Cincinnati's German immigrant community — where trust was extended readily to a familiar face offering care to the elderly. She systematically cultivated relationships with vulnerable men, positioning herself as a caretaker before collecting inheritances, loans, and cash that her victims did not survive to reclaim. The pattern held across at least five deaths spanning four years before an autopsy finally drew official scrutiny. When Ohio executed her in 1938, she became the first woman put to death in the state's electric chair.

Operating in the chaotic postwar border zone between East and West Germany, Pleil exploited the legal vacuum created by divided police jurisdictions and the desperation of people seeking illegal passage across the zonal boundary. His victims were largely women paying to cross the border — isolated, undocumented, and easy to disappear. The nickname he cultivated, Der Totmacher, was largely self-assigned, reflecting a degree of pride in what he had done that unsettled investigators and courts alike; he died by suicide in prison before fully accounting for all the deaths he claimed.