Personality disorders are common in stalkers. Read about the psychological characteristics of the stalker and how to cope with a stalker.

Stalking is a crime and stalkers are criminals. This simple truth is often ignored by mental health practitioners, by law enforcement agencies, and by the media. The horrid consequences of stalking are typically underestimated and stalkers are mocked as eccentric and lonely weirdoes. Yet, stalking affects one fifth of all women and an unknown number of men – and often ends in violence and bloodshed.

A 1997 Review Paper titled "Stalking (Part I) An Overview of the Problem", Karen M Abrams, MD, FRCPC1, Gail Erlick Robinson, MD, DPsych, FRCPC2, define stalking thus:

"Stalking, or criminal harassment, is defined as the 'wilful, malicious, and repeated following or harassing of another person', usually requiring a 'credible threat of violence' against the victim or the victim's family (1). 'Harass' refers to wilful conduct directed at a person that seriously alarms, annoys, or distresses the person and which serves no legitimate purpose (2). Typically, the behaviour involves such things as loitering near the victim, approaching, making multiple phone calls, constantly surveilling, harassing the victim's employer or children, harming a pet, interfering with personal property, sabotaging dates, and sending threatening or sexually suggestive 'gifts' or letters. The harassment usually escalates, often beginning with phone calls that gradually become more threatening and aggressive in nature, and frequently ends in violent acts (3). In essence, the offender's behaviour is terrorizing, intimidating, and threatening, and restricts the freedom of and controls the victim.

In the US, there are individual state laws but no unified federal antistalking laws. Under the Criminal Code of Canada, it is a crime to knowingly or recklessly harass another person in any of the following ways: 1) by repeatedly following or communicating either directly or indirectly with that person or anyone known to them; 2) by watching where that person or anyone known to them resides, works, or happens to be; or 3) by engaging in any threatening conduct directed at that person or his or her family, if any of these cause the person to reasonably fear for his or her safety (4). In both the US and Canada, antistalking laws are in a state of flux."

Many criminals (and, therefore, many stalkers) suffer from personality disorders – most prevalently, the Antisocial Personality Disorder, formerly known as "psychopathy". Co-morbidity – a "cocktail" of mental health disorders – is frequent. Most stalkers abuse substances (alcohol, drugs) and are prone to violence or other forms of aggression.

APD or AsPD was formerly called "psychopathy" or, more colloquially, "sociopathy". Some scholars, such as Robert Hare, still distinguish psychopathy from mere antisocial behaviour. The disorder appears in early adolescence but criminal behaviour and substance abuse often abate with age, usually by the fourth or fifth decade of life. It may have a genetic or hereditary determinant and afflicts mainly men. The diagnosis is controversial and regarded by some scholar as scientifically unfounded.

Psychopaths regard other people as objects to be manipulated and instruments of gratification and utility. They have no discernible conscience, are devoid of empathy and find it difficult to perceive other people's nonverbal cues, needs, emotions, and preferences. Consequently, the psychopath rejects other people's rights and his commensurate obligations. He is impulsive, reckless, irresponsible and unable to postpone gratification. He often rationalises his behaviour showing an utter absence of remorse for hurting or defrauding others.

Their (primitive) defence mechanisms include splitting (they view the world – and people in it – as "all good" or "all evil"), projection (attribute their own shortcomings unto others) and Projective Identification (force others to behave the way they expect them to).

The psychopath fails to comply with social norms. Hence the criminal acts, the deceitfulness and identity theft, the use of aliases, the constant lying, and the conning of even his nearest and dearest for gain or pleasure. Psychopaths are unreliable and do not honour their undertakings, obligations, contracts, and responsibilities. They rarely hold a job for long or repay their debts. They are vindictive, remorseless, ruthless, driven, dangerous, aggressive, violent, irritable, and, sometimes, prone to magical thinking. They seldom plan for the long and medium terms, believing themselves to be immune to the consequences of their own actions.