The typical serial killer is defined as male Caucasian, aged 18-32. However, there are serial murderers from all other races and ages. Also there are women among them, although their number is significantly smaller compared to men. Most serial killers are heterosexual but there are exceptions to this too. The majority of serial murderers are solitary individuals, although there are exceptions of pairs of individuals killing together. The FBI says that most serial killers are looking for sensation, do not feel guilt and have a predatory behavior. They are also impulsive and need to control their victims. These characteristics are typical for psychopaths who cannot distinguish right from wrong, do not care and are not capable of feeling empathy. However the FBI says that not all psychopaths become serial killers. Another group of serial killers are the psychotics. They have severe mental diseases that include symptoms like hearing voices, or having visions. This type of serial murderer is less common. These killers commit their crimes due to their disease and not because they want to.
The FBI's Behavioral Science Unit (BSU) classifies serial killers as asocial or non-social. Asocial killers are disorganized and pick their victims in the areas where they live or work. They leave evidence, at the crime scene, of little preparation or total lack of preparation for the murder. Asocial serial killers tend to knock their victims unconscious before killing them. The non-social serial killers, on the contrary, are organized and more creative. They are more adaptive and mobile, with conventional relationships. The non-social serial killers tend to have a preferred type of victims and kill them slowly. They want to shock the community and most often leave the dead bodies in public view. According to the FBI, the majority of serial killers are social misfits who live alone. Many of them have families and homes, are well employed and appear to be normal members of the community. For that reason serial killers are harder to detect by the police and investigators than other criminals. FBI data show that most serial killers have very defined geographic areas of operation. They conduct their killings within comfort zones, such as a place of residence or employment, or the residence of a relative. When their confidence grows, serial killers start expanding their activities outside the comfort zones.
Psychologist Dr. Joel Morris, a founding member of the International Committee of Neuroscientists to Study Episodic Aggression, says that serial killers go through seven phases: aura, day dreams and fantasies; trolling, cruising and contact; wooing, luring into clutches; capture; murder; totem, collection of trophies and souvenirs; and depression, post-homicidal deflation. According to FBI reports, predisposition to serial killing is biological, social and psychological in nature, without being limited to any specific characteristic or trait. The development of a serial killer involves a combination of these factors. However, the FBI says that there is no generic template for a serial killer, but these murderers are driven by their own unique motives or reasons. Most serial killers have average or above average intelligence. Often they have been raised in problematic families where they have been exposed to cruelty, sexual abuse and sometimes long and systematic torture. However, some serial killers have a good social background. It has been widely believed that once serial killers start killing, they cannot stop. However, FBI data shows that some serial killers stop murdering altogether before being caught. Usually events or circumstances in offenders' lives are the reason to stop pursuing more victims. These can include increased participation in family activities, sexual substitution and other diversions.