A pioneer in the study of psychopathy whose influential work, The Mask of Sanity, provided early clinical descriptions of psychopathy. His research significantly influenced Hare's development of his psychopathy checklist.

An infamous American serial killer from the 1970s, referenced in the book to illustrate common traits of a psychopath, including superficial charm and lack of remorse. His case is used to highlight both the public perception and complexity of psychopathy.

An American serial killer who committed numerous murders in the 1970s. He is discussed in the book to exemplify how psychopaths can hide behind a facade of respectability and use manipulation to carry out their crimes.

Referenced in the book as an example of female psychopathy, she attempted to kill her children and is used to show the traits of irresponsibility and lack of genuine emotion in psychopathic behavior.

A significant case study in the book as Hare's first professional encounter with a psychopath. His interactions with Hare highlight the manipulative and charming traits often associated with psychopathy.