We know of psychopaths from chilling headlines and stories in the news and movies – from Ted Bundy and John Wayne Gacy, to Hannibal Lecter and Dexter Morgan. As Dr. Kent Kiehl shows, psychopaths can be identified by a checklist of symptoms that includes pathological lying; lack of empathy, guilt, and remorse; grandiose sense of self-worth; manipulation; and failure to accept one’s actions. But why do psychopaths behave the way they do? Is it the result of their environment – how they were raised – or is there a genetic compo­nent to their lack of conscience?