Please Note: The following information is copied and reproduced here from a US web site thebitchnextdoor.com unfortunately the site is no longer available however the information is very good.
Antisocial Personality Disorder (Sociopathy)
Antisocial personality disorder, or, as it is more commonly referred to, Sociopathy, is characterized by actions that consistently fail to conform to public social norms, consistent lying, cheating and stealing to get what they want, willingness to complete ignore the rights and boundries of others with a complete lack of empathy for the distress that their actions cause to others.
The issue of most concern is that sociopaths will, without any regard for themselves or others, resort to acts of aggression and violence without any real thought. For this reason, if possible, any sign of anger or irritation should be a strong cue to anyone to get out of the area, and just avoid this person at all costs. Getting into a fight is one thing, but anger from a sociopath can lead to a long terms feud of violent acts.
These people sometimes develop a very superficial charm that they use to get away with their actions. This is read by many people, however, often even the people it does work on end up seeing the truth at some point. Sociopaths commonly have a hard time making friends, and an even more difficult time keeping them. They are very narcissistic in terms of the sociopath also having that same sense of personal entitlement, a willingness to take advantage of people to reach their goals and having to empathy for the people they hurt in the process.
Officially antisocial personality disorder can not be diagnosed before the age of 18, but there are markers that can indicate the possible future diagnosis with younger children. Younger children that are known to be later diagnosed as sociopathic have longer than average periods of bed wetting, they show behaviors of extreme cruelty toward animals and an interest in burning things, or, pyromania.
It is impossible to know how many people with those markers develop into diagnosed sociopaths, however, a large percentage of diagnosed sociopaths do have those three markers in their personal histories.
Exact causes of this disorder are not known, however, parents that are antisocial have an increased likelihood of raising antisocial children. Alcoholism of the father seems to increase the likelihood of the child becoming antisocial. Children that lack maternal attention for the first five years of life has been found to be a factor, as has a lack of consistent parental discipline and attention. These factors lead to an unpredictable home that oes not teach consistent rules for behavior.
Dealing with a Sociopath
Dealing with Sociopaths, more politically correctly known as "antisocial personality disorder" is impossible. They can live among normal society by blending in pretty easily, however, it's the people that befriend them, work with them, or are otherwise just general to close to them, they get hurt. They have no conscience as normal people know it, they do what they want, to who they want, when they want and never feel badly about it.
While it is subject to debate, many mental health professionals hold the belief that therapy actually makes sociopaths worse, as in the process of therapy they learn new vulnerabilities to exploit in "normal" people. It is commonly accepted that sociopaths are not treatable.
The only way to deal with a sociopath is to keep your distance, get them out of your life. Do it discreetly and do not make a big dramatic case out of it. Remember who you are dealing with and handle your separation with care so as not to offend or anger the sociopath in question. Angering or offending somebody with no conscience can have nothing but bad outcomes for you.
Be smart, be safe, be distant. While a good "get even" may feel good for a brief moment, the consequences could be bad, for a seriously sociopathic person, it could be harmful and violent.
One thing you certainly do not want to do is get into a vengence contest against somebody with no conscience.