Stalker

A Stalker is defined as one who engages in the act of stalking another individual.

Legal Definition
Stalking may involve the unwanted attention, harassment or the following or watching of another individual. Depending on the degree of stalking, it may or may not be considered a crime. There are actually quite a few cities in which the act of stalking (as legally defined) is not a crime. New York City is one example.

Psychological Definition
In psychology, a stalker may believe that his/her victim(s) have genuine feelings for them, and may try passive means to get noticed. These may include harmless acts such as sending flowers or constantly "bumping" into the person on the street. While these actions may cause discomfort or fear in the victim, these types of stalkers are generally harmless.

In extreme cases, the stalker may crave the feelings of fear that the victim(s) may express. He or she may repeatedly try to make contact, after being asked not to, or send unusual gifts (e.g. nude photos of themselves, or compromising photos of the victim). These tactics are usually shown in stalkers who want their victims to know they are being watched.

Types of Stalkers

 * Rejected stalkers pursue their victims in order to reverse, correct, or avenge a rejection (e.g. divorce, separation, termination).
 * Resentful stalkers pursue a vendetta because of a sense of grievance against the victims – motivated mainly by the desire to frighten and distress the victim.
 * Intimacy seekers seek to establish an intimate, loving relationship with their victim. To them, the victim is a long-sought-after soul mate, and they were 'meant' to be together.
 * Incompetent suitors, despite poor social or courting skills, have a fixation, or in some cases a sense of entitlement to an intimate relationship with those who have attracted their amorous interest. Their victims are most often already in a dating relationship with someone else.
 * Predatory stalkers spy on the victim in order to prepare and plan an attack – usually sexual – on the victim.

On Criminal Minds

 * Season One:
 * Vincent Shyer ("Broken Mirror")
 * Walter Kern ("Unfinished Business")
 * Maggie Lowe ("Somebody's Watching")
 * Randall Garner ("The Fisher King, part 1" and "The Fisher King, part 2")
 * Season Two:
 * William Lee ("Aftermath")
 * Season Three:
 * Max Pool ("About Face")
 * Jason Clark Battle ("Penelope")
 * Mike Hicks ("The Crossing")
 * Season Four:
 * Gary Michaels ("Memoriam")
 * Ian Coakley ("Roadkill")
 * Season Five:
 * Joe Belser ("The Slave of Duty")
 * Robert Johnson ("The Internet Is Forever")
 * Season Six:
 * Jane Gould ("Today I Do")
 * Greg Phinney ("The Stranger")
 * Season Seven:
 * Ben Bradstone ("Proof")
 * George Kelling ("From Childhood's Hour")
 * Bill Rogers ("Hope")
 * Hamilton Bartholomew ("Unknown Subject")
 * Malcolm Ford ("The Company")
 * Season Eight:
 * John Curtis ("The Silencer", "The Apprenticeship", "Magnificent Light", "Zugzwang", "Broken", "Carbon Copy", "Brothers Hotchner", and "The Replicator")
 * Arthur Rykov ("Through the Looking Glass")
 * Diane Turner ("Zugzwang")
 * Donnie Bidwell ("Carbon Copy")
 * Mark Jackson ("The Gathering")
 * Peter Harper ("The Gathering")
 * Tory Chapman ("Pay It Forward")
 * Johnny Ray Covey ("Nanny Dearest")
 * Season Nine:
 * Tanner Johnson ("Gatekeeper")
 * Daniel Milworth ("The Caller")

Real World

 * Robert John Bardo - Stalked actress Rebecca Schaeffer, whom he later killed
 * John Hinckley, Jr. - Stalked actress Jodie Foster and 39th President of the United States Jimmy Carter
 * Richard Farley - Stalked coworker Laura Black, whom he later wounded during a massacre
 * John Wilkes Booth - Stalked 16th President of the United States Abraham Lincoln months before assassinating him

Resources

 * DSM-IV-TR® Diagnostic and Statistical Manual of Mental Disorders