He [Dr Robert Hare] defines psychopathy as "a personality disorder characterised by a cluster of personality traits and associated behaviours, including lack of empathy or remorse, a grandiose approach to the world, superficiality, concern with number one, impulsivity, things of that sort".
Other core characteristics are shallow emotions, lying, glibness and great skill at manipulation.
"These are essentially people with a lack of conscience," Hare says. "They intellectually work out how you feel, but really they have no idea of emotion at all. They're a colour-blind person trying to understand colour."
...clinicians who use these manuals look for symptoms in people over 18 and not otherwise psychotic who since age 15 have shown a pervasive pattern of disregard for, and violation of, the rights of others.� Among these behaviors, the person has done at least three of the following:
failure to conform to lawful social norms
deceitfulness
impulsivity or failure to plan ahead
irritability and aggressiveness, as indicated by repeated physical fights or assaults
reckless disregard for safety of self or others
consistent irresponsibility, as indicated by repeated failure to sustain consistent work behavior or honor financial obligations
lack of remorse, as indicated by being indifferent about having hurt, mistreated, or stolen from another

Refocusing the idea of antisocial personality disorder, psychopathy is characterized by such traits as:
lack of remorse or empathy
shallow emotions
manipulativeness
lying
egocentricity
glibness
low frustration tolerance
episodic relationships
parasitic lifestyle
persistent violation of social norms

It remained to translate the academic and professional work into a form that ordinary people could understand, so in 1993, Hare published Without Conscience.� His purpose was to warn people about those predators who walked among them, and to provide a way for those with shattered lives as the result of an encounter with a psychopath to deal with it.� He believes that, for their own protection, it's crucial that people learn to identify a psychopath who may be very close to them.�

Too many people hold the idea that psychopaths are essentially killers or convicts.� The general public hasn't been educated to see beyond the social stereotypes to understand that psychopaths can be entrepreneurs, politicians, CEOs and other successful individuals who may never see the inside of a prison and who don't commit violent crimes.� However, they do often commit violations of another sort: They exploit people and leave them depleted and much the worse for the encounter.� They prove to be treacherous employees, conniving businessmen, or immoral officials who use their position to victimize people and enrich themselves.