According to popular wisdom, psychopaths are crazed and bloodthirsty serial killers. The reality is not so simple. While many psychopaths do commit violent crimes, not all psychopaths are criminals and not all criminals are psychopathic. Equinox reports on techniques developed by psychologists to work out whether a person is psychopathic and shows how brain scientists are coming close to mapping the malfunctions in the brain that cause a person to be a psychopath.