This is from sources on the web, and is based on Robert Hare's psychopathy checklist.
1. Look for glib and superficial charm. A psychopath will also put on what professionals refer to as a 'mask of sanity' that is likable and pleasant. It is a thin veneer.
2. Look for a grandiose self perception. Psychopaths will often believe they are smarter or more powerful than they actually are.
3. Watch for a constant need for stimulation. Stillness, quiet and reflection are not things embraced by psychopaths. They need constant entertainment and activity.
4. Determine if there is pathological lying. A psychopath will tell all sorts of lies; little white lies as well as huge stories intended to mislead. Psychopaths are gifted or dull, high functioning or low performing like other people. An untalented psychopath may harm a few; a highly talented psychopath may lay waste to nations. The difference between the psychopath and others lies in their organic lack of conscience and empathy for others. The sociopath is trained to lack empathy and conscience. The psychopath is a natural.
5. Evaluate the level of manipulation. All psychopaths are identified as cunning and able to get people to do things they might not normally do. They can use guilt, force and other methods to manipulate.
6. Look for any feelings of guilt. An absence of any guilt or remorse is a sign of psychopathy. They will often blame the victim.
7. Consider the level of emotional response a person has. Psychopaths demonstrate shallow emotional reactions to deaths, injuries, trauma or other events that would otherwise cause a deeper response. Other people are satisfaction suppliers, nothing more.
8. Look for a lack of empathy. Psychopaths are callous and have no way of relating to others in non-exploitative ways. They may find a temporary kinship with other psychopaths and sociopaths that is strictly utilitarian and goal-oriented.
9. Psychopaths are often parasitic. They live off other people, emotionally, physically, and financially. Their modus operandi is domination and control. They will claim to be maligned or misunderstood to gain your sympathy.
10. Look for obsessive risk taking and lack of self-control. The Hare Checklist includes three behavior indicators; poor behavior control, sexual promiscuity, and behavioral problems.
11. Psychopaths have unrealistic goals or none at all for the long term. Either there are no goals at all, or they are unattainable and based on the exaggerated sense of one's own accomplishments and abilities.
12. Psychopaths will often be shockingly impulsive or irresponsible. Their shamelessness knows no bounds. You will ask, what were they thinking? And the answer was, they weren't because they did not care.
13. A psychopath will not genuinely accept personal responsibility. A psychopath will never admit to being wrong or owning up to mistakes and errors in judgment, except as part of a manipulative ploy. They will despise and denigrate their victims once they are done with them. If they have any regret it is that their source of satisfaction supply has ended and they must seek another.
14. Psychopaths lack long term personal relationships. If there have been many short term marriages, broken friendships, purely transactional relationships, the chances the person is a psychopath increase. Watch especially how they treat other people in weaker positions and even animals.
15. Psychopaths are often versatile in their criminality. Psychopaths are able to get away with a lot, and while they might sometimes get caught, the ability to be flexible and adaptable when committing crimes is indicative.
If you should find yourself in a business or personal relationship with a psychopath, the best advice is seek counseling if you need, obtain assistance if you must, and run if you can. You are a diffused and multi-faceted person with many interests. A psychopath is powerfully focused on obtaining what he wishes from others, without many prohibitions or distractions. Avoidance is the best policy. Long term confinement is their best treatment.
I do not think the repetitive sociopathic behaviours and psychopathic tendencies of the Roman imperial leadership to be accidental. The mad emperors kept recurring because they were the creatures of what that culture had become, and they stood as emblems at its apex.
Men are social animals, and can go mad in groups, as well as alone. Psychopathy can be the black hole at the center of a whole galaxy of madness and sociopathy under the right conditions, and the results can be flamboyantly destructive, as we most recently saw in several places during the 20th century.
The psychopaths can thrive anywhere that deception is an advantage, but their prime hunting ground is a system in crisis, a manageable chaos lacking transparency, a well defined rule of law, and effective enforcement of behaviour.