Psychologist reveals the three disturbing childhood traits linked to future serial killers

True crime obsession is at an all-time high right now, especially with Ryan Murphy’s latest series, Monster: The Ed Gein Story, giving people a front-row seat to the dark minds behind some of history’s most infamous killers. But while it’s fascinating to watch these horrific stories unfold on screen, psychologists say that there are three childhood signs which could signal a future serial killer.

Known as the Macdonald Triad, this theory was first proposed in the 1960s by psychiatrist J.M. Macdonald in his article The Threat to Kill. Macdonald studied 100 patients who had threatened violence and observed a pattern: Three specific behaviours that could act as early warning signs of antisocial or violent tendencies.

So, what are these behaviours? The Macdonald Triad identifies them as cruelty to animals, obsession with fire-setting, and persistent bedwetting beyond the typical developmental age.

Animal cruelty

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Repeatedly harming or killing animals in childhood can indicate a lack of empathy and enjoyment in dominating weaker beings. Experts note that while not all children who harm animals grow into violent adults, this behaviour is perhaps the most concerning of the three.

Serial killers such as Jeffrey Dahmer reportedly displayed this trait, enjoying the killing and dissection of animals in his youth. Similarly, Ted Bundy was known to have tortured animals during his childhood, suggesting an early fascination with control and suffering.

Fire-setting 

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A compulsive fascination with starting fires can indicate underlying anger or thrill-seeking tendencies.

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Charles Manson, for instance, had a documented history of setting fires as a child, hinting at early behavioural disturbances that later manifested in more extreme forms. Psychologists caution, however, that many children play with fire out of curiosity.

Persistent bedwetting

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Bedwetting beyond age five may not seem threatening, but within the triad, it is linked to poor emotional regulation or childhood trauma.

John Wayne Gacy, infamous for his murders in the 1970s, reportedly struggled with bedwetting, highlighting the stress and humiliation that some of these childhood traits can involve.

While the Macdonald Triad remains a useful lens for understanding early signs of trauma or emotional distress, no single trait guarantees violent tendencies. Instead, these behaviours often point to deeper issues that require attention, care, and early intervention.

While chilling, the triad is less a crystal ball for predicting future murderers and more a warning to watch for children struggling with underlying trauma, because catching problems early can make all the difference.

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Featured image credit: Netflix