More than 5,000 serial killers have been documented throughout human history, spanning a wide range of motives, behaviors and backgrounds.
By studying these cases, we can gain insight into the complex factors that lead to such extreme and harmful actions.
Understanding these cases empowers us to strengthen our efforts in crime prevention and mental health support. Read on to learn more about serial killers and how this knowledge is used to prevent future heinous crimes.
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The definition of serial killer is a heavily debated topic among professionals.
According to the FBI's definition, which is commonly cited as the standard, what identifies someone as a serial killer is a specific behavior: having killed two or more victims in separate incidents.
In contrast, a spree murder happens when a person kills two or more people without taking a break in between. This differs from a serial murder, where there is typically a pause, known as a "cooling off period" between each killing.
"No other personality or behavioral characteristic places all serial killers into a criminological category," Dr. Katherine Ramsland, a professor of forensic psychology at DeSales University and an author, told Fox News Digital. "Although some subgroups have core behaviors in common, there's a lot of variation in this population, from a range of motives, backgrounds, ages and behaviors, to differences in physiology, mental state and perceptions that influence reasoning and decisions. Many are psychopathic, some are psychotic."
The differences between serial killers can be striking. Some operate with meticulous planning and premeditation, carefully selecting and stalking their victims.
Others act impulsively, driven by sudden urges or fantasies. Motives can range from power and control to delusional beliefs.
The paths that lead people to commit these horrific acts add another layer of complexity. Some have experienced severe trauma or abuse, while others show signs of underlying mental health issues.
The chilling cases of serial killers often captivate widespread public attention, but they are frequently entwined with misinformation.
An example of this is the outdated organized vs. disorganized typology in criminal profiling.
This typology was once a cornerstone of criminal profiling, but the FBI has moved away from this due to its oversimplification of complex behaviors, Ramsland told Fox News Digital.
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She added that such classifications have fallen out of favor in modern forensic psychology.
However, examining these characteristics can still provide insights into different patterns of behavior among offenders.
An organized offender typically has an IQ in the above-average range, paired with socially adequate behavior. This combination often allows them to blend into society and maintain relationships. On the other hand, a disorganized offender may have a lower IQ and struggle with social skills, leading to social inadequacy.
While not all individuals with mental illness are violent or engage in criminal behavior, there are cases where mental health issues can contribute to or coincide with serial killing behaviors.
Many serial killers exhibit traits of psychopathy, while some experience psychotic symptoms, Ramsland told Fox News Digital.
Psychopathy, which is a personality disorder characterized by a lack of empathy, manipulative behavior, superficial charm and a tendency toward impulsivity and antisocial behavior.
Psychopathic individuals often display a callous disregard for the rights and feelings of others, making them more likely to engage in predatory or violent acts without remorse.
Some individuals may experience psychotic symptoms, such as hallucinations, delusions or disorganized thinking, which can significantly impact their perception of reality. Psychotic serial killers may believe they are acting on external commands or experiencing distorted beliefs that fuel their violent actions.
The so-called MacDonald Triad, which includes bedwetting, animal cruelty and fire-setting, has also been debunked, Ramsland told Fox News Digital.
Not all serial killers or violent offenders exhibit the MacDonald Triad. Many individuals who engage in these behaviors do not go on to commit violent crimes.
While there may be a statistical association between these behaviors and future violence, one does not necessarily cause the other.
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To identify potential serial killers, it’s critical to focus on key behaviors rather than trying to fit people into specific criminal categories.
There is no universal profile for all serial killers, as they all vary depending on each case.
"[Children at risk for becoming offenders] won't necessarily become killers, let alone serial killers, but they're more likely, when violent, to be sadistic and destructive," Ramsland said. "Those traits would be callousness, cruelty and disinhibition, known as the triarchic model for children. Unmotivated lying is also part of it, as is not taking responsibility for one's behavior and tending to blame others."
Working closely with young people at risk is best done through cognitive behavioral approaches that use reward systems, Ramsland told Fox News Digital.
While there is currently no proven intervention strategy, the Mendota Juvenile Treatment Center in Wisconsin is one of the leading models for success, she added.
The Mendota center is a specialized residential facility located in Madison that focuses on the treatment and rehabilitation of juvenile offenders with serious behavioral and mental health issues.
The most common methods of catching serial killers include situations where the victim survives, DNA evidence, tips from associates, family members, or friends, fingerprint matches, prior criminal records, discoveries of bodies in homes and arrests made for unrelated offenses, according to the National Institutes of Health.
Knowing common characteristics helps law enforcement identify potential suspects and create profiles that can guide investigations.
For example, if a series of murders exhibits patterns such as victim type, method of killing or location, this information can be used to narrow down the pool of suspects.
Understanding the characteristics of serial killers is an important tool used by law enforcement to prevent future crimes by serial offenders.
This knowledge allows for proactive measures that can save lives and ultimately bring criminals to justice.
