How to spot a serial killer: Analysis of 45 murderers finds 4 traits

Psychologists have revealed how you can spot a potential serial killer – and say there are four key traits to look out for. 

The researchers at the University of Bamberg in Germany analysed statements from 45 sexually-motivated serial killers, active across 60 years.

Results show they were motivated by four distinct narcissistic traits – ‘grandiose rivalry’, ‘grandiose admiration’, ‘vulnerable isolation’ and ‘vulnerable enmity’. 

Grandiose rivalry is defined as the devaluation of others and striving for supremacy, while grandiose admiration is typified by self-promotion and an extreme need for admiration.

Vulnerable enmity comprises paranoia, aggression and a belief one is being treated unfairly, while vulnerable isolation is withdrawing from social situations to protect a fragile self-esteem. 

Study author Evangelia Ioannidi said the psychology of serial killers is ‘more complex’ than people usually assume.

That’s because serial killers possess vulnerability as well as ‘grandiosity’ (full of self-importance, arrogance and a need for superiority). 

‘These offenders aren’t driven only by ego or the desire to feel powerful,’ Ioannidi, a psychologist and criminologist at the University of Bamberg, 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.’ 

For the study, Ioannidi and colleagues used the Radford/FGCU Serial Killer Database, which contains records of over 1,043 individuals.

A serial killer is recognised by the FBI as ‘the unlawful killing of two or more victims by the same offender(s), in separate events’, although other sources put it as three or more.

From the database, the experts identified 45 male serial killers active between 1960 and 2021 whose killings were primarily sexually motivated.

All 45 killers had acted independently, not as part of a group or gang, and ‘had been found legally competent to stand trial and convicted’. 

Shockingly, the number of victims ranged from two to 22 per offender, with an average of 8.04 victims. 

The team analysed confessions and interrogation interviews from the serial killers, either publicly available or obtained upon request. 

According to the researchers, vulnerable enmity was found in 84 per cent of the statements (38 cases) – making it the top trait across the 45 serial killers. 

Meanwhile, vulnerable isolation appeared in 58 per cent of cases (26 statements), grandiose admiration in 76 per cent (34 statements) and grandiose rivalry in 71 per cent (32 statements).

Researchers found there was typically significant overlap between the traits, which rarely existed in isolation. 

So serial killers likely possess a balance of the four traits – meaning they have a grandiose, showy exterior to go along with their vulnerable, more-inward facing side. 

The findings highlight ‘the pronounced presence of both vulnerable and grandiose narcissism in sexually motivated serial killers’, according to the team. 

‘[We] provide a more nuanced understanding of how different narcissistic dimensions may coexist and interact in this offender group,’ they say. 

‘These traits deepen our knowledge of psychological mechanisms present in sexually motivated serial killers.’ 

However, in their new paper, published in the Journal of Police and Criminal Psychology, the team warn that the four traits ‘should not be interpreted as direct or exclusive predictors of such extreme violence’.

As we know from a legion of previous studies, narcissistic tendencies are also present in many individuals who never engage in criminal behaviour. 

According to one study earlier this year by psychologists at Georgia Southern University, the more someone admires celebrities, the more likely they are to have vulnerable narcissism.  

Meanwhile, men with a high sex drive or ‘libido’ are more likely to be a narcissist, found experts at the University of British Columbia. 

Narcissistic men are also more prone to premature ejaculation and difficulty reaching orgasm, a 2022 study found. 

Another recent study linked eating meat with the personality disorder, particularly if the person provides a ‘hierarchical justification’ such as ‘humans are at the top of the food chain’.