A serial killer is an individual who murders a series of victims over a period of time, typically with gaps between each killing. Some serial killers kidnap and/or torture their victims prior to murdering them. While it’s not always clear what motivates serial killers to commit such heinous acts, abnormal psychological processes—notably severe antisocial tendencies—are to blame. In society, serial killers often generate fascination along with fear; their crimes tend to bring notoriety, media attention, and “fans” who study their crimes or, in some cases, form relationships with the murderer.
Historians argue that serial killers have existed throughout history. In ancient and medieval times—long before the concept of a “serial killer” entered popular parlance—such murders were often thought to be the work of monsters, werewolves, or witches; when they were caught, many serial killers of the time were accused of (or even confessed to) committing the murders for "supernatural" purposes.
Though Jack the Ripper—an unidentified murderer who was active in the late 19th century—is often called the "first modern serial killer," the term “serial killer” itself was popularized in the latter half of the 20th century, when such murderers began to receive more significant media attention and drew heightened focus from increasingly sophisticated law enforcement agencies. Most of the most famous documented serial killers were active in the 20th or 21st century—coinciding both with increased public interest in serial killers’ stories, as well as with a heightened understanding of what motivates them, how they develop, and how, perhaps, their violent crimes can be prevented.
Most experts define a serial killer as someone who has murdered at least three people, over a period of more than a month, with at least some “cooling-off” time between each murder. Some criminal psychologists go further, arguing that serial killers must have a deviant psychological motive—for example, sexual gratification—that goes beyond the murder itself.
Serial killers and mass murderers both commit multiple homicides. However, serial killers typically commit the murders over an extended period and allow time to elapse between each. Mass murderers, by contrast, commit all their murders in a brief, one-time event. A school shooter, for instance, is considered a mass murderer rather than a serial killer.
Serial killers have been reported in most countries and on six continents. While Western countries—including the U.S.—tend to have more known serial killers than non-Western countries, experts speculate that this is likely due to increased media attention and better law enforcement efforts, rather than an actual increased prevalence of serial killers.
Serial killers are categorized by motivation. Visionary killers believe they are being “ordered” to commit murder by God or another entity; these killers may have schizophrenia or experience a psychotic break shortly before committing their crimes. Mission-oriented serial killers consider it their “duty” to rid the world of certain people—sex workers, for instance. Hedonistic killers derive pleasure from killing, either sexual or thrill-based. Other serial killers are driven by a need for power and/or control.
Criminal psychologists, law enforcement agencies, and the general public have long been interested in what motivates serial killers to commit their terrible crimes. Because most “normal” people could never imagine doing the same, another question that draws serious interest is whether or not serial killers can be said to suffer from severe mental illness that severs their contact with reality.
But while some serial killers did appear to undergo psychotic breaks that triggered their crimes, overall, serial killers have rarely been found to be legally insane. Rather, the most consistent psychological feature among serial killers appears to be extreme antisocial behavior—they tend to lack empathy, appear incapable of remorse, show no regard for laws or social norms, and have a strong desire to revenge themselves against individuals or society at large by carrying out violent, terrifying crimes.
It depends. Some serial killers do exhibit symptoms of psychosis, while others are diagnosed with severe bipolar disorder. However, very few serial killers are considered mentally ill enough to be declared legally insane. Rather, the majority display signs of psychopathy or sociopathy; in terms of diagnosis, they may meet the criteria for antisocial personality disorder.
Most serial killers demonstrate antisocial tendencies—including a lack of empathy, a disregard for laws and the rights of others, and a lack of remorse—and many meet the criteria for either psychopathy or sociopathy. Some serial killers, however, have been diagnosed with psychosis, schizophrenia, or another personality disorder, in addition to or instead of psychopathy.
Though popular media—such as the film “Silence of the Lambs”—often depict serial killers as “evil geniuses,” most of them are in fact of average IQ. Like the general population, serial killers’ intelligence falls on a spectrum—some are of very low IQ, while a few others have demonstrated unusually high intelligence.
The question of whether serial killers are the result of nature or nurture has long fascinated psychologists. Many serial killers suffered terrible childhood abuse, suggesting an environmental component. However, antisocial personality disorder—thought to be present in many serial killers—has significant genetic roots; thus, DNA likely influences the later development of extreme homicidal tendencies.
Most serial killers have some early history of trauma or neglect; some, but not all, also engage in early delinquent behavior. A well-known concept, the “Macdonald triad,” posits that repeated violent offenders share three early traits: animal cruelty, fire-setting, and bedwetting. However, this “triad of evil” is not universally present among serial killers.
Yes. The majority of documented serial killers are male, but women have also committed many such murders throughout history. Some experts estimate that women comprise approximately 15 percent of serial killers. Stereotypes of women as nurturing or submissive likely fuel the myth that all serial killers are men.
Female serial killers may differ from their male counterparts in key ways. They appear significantly less likely to be driven by sexual motivations; they may also be more prone to kill for financial gain. They favor poison and other less “messy” means to kill than do men, who tend to shoot, stab, or strangle victims. Women who engage in serial killing often act in concert with a man, serving as partners in crime, as was the case with Karla Homolka and Myra Hindley, who worked with Paul Bernardo and Ian Brady, respectively.
Serial killers commit horrible crimes that should—and do—repulse us. But alongside the disgust and fear that serial killers trigger, there often exists a morbid curiosity: We want to learn more about them and examine why they do what they do. This is the case for both individuals and society as a whole; indeed, the societal fascination with serial killers can be seen in the countless books, TV shows, podcasts, and movies about serial killers, not all of which paint the murderers in a purely negative light.
But while it certainly is possible for an interest in serial killers to go too far, a fascination with evil is not inherently psychologically unhealthy. Some experts posit that interest in serial killers is fueled by our general desire to understand the unknown and to feel secure in our own lives; similarly, serial killer fascination may offer a safe outlet for dark thoughts and urges that everyone—even those who would never hurt another person—experiences.
Our brains are programmed to pay attention to calamity; an interest in serial killers fulfills this psychological need. True crime often provides an adrenaline rush that can be pleasurable when experienced in a safe environment. That serial killers tend to appear “normal” until caught can also fuel a desire to learn the “signs” so as to not be caught unawares.
“True crime” is a popular genre, and serial killers provide prime material. This is likely because fascination with murder exists in many to some degree. Consuming such media allows someone to experience fear and horror in a controlled environment. It may also provide psychological safety or a feeling that one is armed with knowledge.
Despite the recent increased understanding of serial killers, many societal myths about them continue to persist. These include: They are “evil geniuses” (most are of average intelligence); they are all men (women make up approximately 15 percent of serial killers); and they are dysfunctional loners (many have families and are well-regarded in their communities).
Women who marry or pursue convicted serial killers offer different motivations for doing so; some, for instance, say they wish to “nurture” him after early abuse. Some experts argue that such women are unstable and display extreme fanaticism; others, however, posit that evolutionarily-driven desires for a “dominant” mate may be at play—albeit in an extreme form.
Serial killers can trigger great fear in the communities in which they operate—possibly leading to increased policing, new laws, or a general distrust of strangers. Some sociological theorists argue that serial killers serve an important social role: by behaving in indisputably despicable ways, they clarify the boundary between “good” and “evil” in the public’s eyes.