New Study Reveals How To Identify A Serial Killer And The Four Traits They Tend To Share

There are four recurring traits, but recognizing a serial killer is still far from simple

A recent study has taken a closer look at how serial killers operate and highlighted several traits that many of them seem to share. The findings have drawn attention because they point to patterns that appeared again and again across different cases.

Psychologists from the University of Bamberg in Germany examined 45 male serial killers whose crimes were motivated by sexual violence. Their work covered a period of 60 years, giving them a wide sample to compare and analyze. The long time frame helped them identify consistent traits rather than short-term trends.

Their research used data from the Radford/FGCU Serial Killer Database, which includes more than 1,040 profiles. From this large collection, the team noticed that most of the men displayed four specific narcissistic traits built around a mix of grandiose entitlement and deep vulnerability. These traits involved resentment, sensitivity to criticism, and strong emotional reactions to feeling wronged.

According to the FBI, a serial killer is defined as the “unlawful killing of two or more victims by the same offender(s), in separate events,” although some experts prefer a threshold of three or more. The difference often comes down to context and how different agencies classify repeat offenders.

A serial killer may not be so easy to findGetty

What are the four common traits of serial killers the study identified?

The study, which appeared in the Journal of Police and Criminal Psychology, grouped the traits into four categories: “grandiose rivalry,” “grandiose admiration,” “vulnerable isolation,” and “vulnerable enmity.” Each one describes a different way in which narcissistic tendencies can influence behavior.

Grandiose rivalry involves putting others down and seeking dominance in most situations. In contrast, grandiose admiration centers on the need to be praised and noticed, even when the attention is not earned. These traits often show up through arrogance or superiority.

The two vulnerable traits, however, point to something less discussed. They suggest that underneath the surface confidence, many serial killers struggled with paranoia, aggression, and a belief that the world was treating them unfairly. These patterns reveal a more complex psychological mix than people usually expect.

Because of these vulnerabilities, many offenders tended to withdraw from social settings or avoid emotional risk, which fits the idea of “vulnerable enmity.” The trait highlights how they often saw others as a threat to their shaken sense of self-worth.

The researchers found these trends by studying 45 men who acted alone between 1960 and 2021. All of the crimes were sexually motivated, allowing the team to focus on a specific offender type and compare personalities across decades.

How do the traits rank in comparison?

The men studied had between two and 22 victims each, with an average of 8.04 victims. These numbers helped the team examine whether certain traits showed up more often among offenders with longer or more violent histories.

After going through interviews and statements from the killers, the researchers discovered that vulnerable enmity appeared in 84 percent of the material they analyzed, making it the most common trait of all four.

Vulnerable isolation appeared in 58 percent of cases. Grandiose admiration followed at 76 percent, while grandiose rivalry showed up in 71 percent of the interviews. Together, the traits painted a picture of offenders who swing between superiority and insecurity.

When it comes to identifying a serial killer, the reality is that it is still incredibly difficult. Even with these common traits, there is no simple checklist that can reliably point to who might become violent.

So, how do you spot a serial killer?

Study author Evangelia Ioannidi explained that the psychology behind these offenders is “more complex” than people often assume. She noted that it is not just about boldness or self-importance, but also about hidden emotional struggles that influence behavior.

“These offenders aren’t driven only by ego or the desire to feel powerful,” the psychologist and criminologist told PsyPost.

“Yes, many show grandiose traits, but an equally important part is the vulnerable side – the resentment, hypersensitivity, and deep sense of being wronged.”

They’re more vulnerable than you may thinkGetty

“Those two sides working together help explain why their violence is so personal and fueled by control.”

“It’s not about excusing them, it’s about understanding that the psychology behind these crimes is more complex than people usually assume.'”

The authors explained that their findings show a “pronounced presence of both vulnerable and grandiose narcissism in sexually motivated serial killers,” highlighting how these two sides can exist together in the same individual.

“[We] provide a more nuanced understanding of how different narcissistic dimensions may coexist and interact in this offender group.”

“These traits deepen our knowledge of psychological mechanisms present in sexually motivated serial killers.”

However, the researchers cautioned that these traits “should not be interpreted as direct or exclusive predictors of such extreme violence,” emphasizing that psychology alone cannot forecast who will become an offender.

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