https://en.wikipedia.org/wiki/Hervey_M._Cleckley

Hervey Milton Cleckley (September 7, 1903 – January 28, 1984) was an American psychiatrist and pioneer in the field of psychopathy. His book, The Mask of Sanity, originally published in 1941 and revised in new editions until the 1980s, provided the most influential clinical description of psychopathy in the twentieth century. The term "mask of sanity" derived from Cleckley's belief that a psychopath can appear normal and even engaging, but that the "mask" conceals a mental disorder. By the time of his death, Cleckley was better remembered for a vivid case study of a female patient, published as a book in 1956 and turned into a movie, The Three Faces of Eve, in 1957. His report of the case (re)popularized in America the controversial diagnosis of multiple personality disorder. The concept of psychopathy continues to be influential through forming parts of the diagnosis of antisocial personality disorder, the Psychopathy Checklist, and public perception.

Film maker Errol Morris, who tried unsuccessfully to interview Cleckley, said in 2012/13: "He's one of the unsung 20th century figures. He created two of the enduring myths – I would call them – of the 20th century...These ideas don't originate with Cleckley, but Cleckley popularized them, he built them up, he sold them – almost as a brand."