New study reveals how to spot a serial killer and the four traits they all have in common

A new study has revealed how to spot a serial killer and some of the traits they all have in common.

Psychologists from the University of Bamberg in Germany have researched 45 male sexually-motivated serial killers from across 60 years and made an interesting discovery.

The research, based on the Radford/FGCU Serial Killer Database, which contains records of more than 1,040 people, found most shared four very distinct narcissistic traits, driven by grandiose entitlement as well as deep-seated vulnerability, resentment and hypersensitivity.

In the eyes of the FBI, a serial killer is identified as the 'the unlawful killing of two or more victims by the same offender(s), in separate events', though others say it is three or more.

A serial killer may not be so easy to find (Getty)

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

The study, published in the Journal of Police and Criminal Psychology, categorised the traits as 'grandiose rivalry', 'grandiose admiration', 'vulnerable isolation' and 'vulnerable enmity'.

The first is defined as the devaluation of others and a strive for supremacy, while the second is linked to a need to be admired.

While many serial killers display arrogance, the other two vulnerable traits also shows they're more likely to struggle with paranoia, aggression and a belief that they are being treated unfairly.

As a result, they might be withdrawn from social situations to protect their fragile ego, hence the 'vulnerable enmity'.

The experts found this based on 45 male serial killers, who acted alone between 1960 and 2021 and whose crimes were sexually motivated.

How do the traits serial killers share rank in comparison?

The number of victims range from two to 22 per killer, with an average of 8.04 victims.

The team analysed interviews from all the serial killers, finding vulnerable enmity was surprisingly common in 84 percent of the statements, making it to the top trait.

Vulnerable isolation came next, appearing in 58 percent of cases, followed by grandiose admiration (76 percent) and grandiose rivalry (71 percent).

As for spotting one, it might not be so easy.

So, how do you spot a serial killer?

Study author Evangelia Ioannidi said the psychology of serial killers is 'more complex' than you might think as it's not just self-importance they exhibit but vulnerability too.

They're more vulnerable than you may think (Getty)

"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.

"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 state their study highlighted the 'pronounced presence of both vulnerable and grandiose narcissism in sexually motivated serial killers'.

"[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, they warn the traits 'should not be interpreted as direct or exclusive predictors of such extreme violence'.