The homicidal triad: Predictor of violence or urban myth?

For at least half a century, legend has told of a "triad" of ominous childhood behaviors -- cruelty to animals, firesetting, and enuresis – said to predict future violence.

The so-called "Macdonald triad" (also known as the homicidal triad or the Hellman and Blackman triad) is taught in criminology and psychology courses, used by forensic practitioners in assessing risk, and has even made its way into Law and Order: Special Victims Unit. Especially, it’s become a staple among aficionados of the trendy serial killer.

But is the syndrome valid?

Providing the most definitive exploration to date is Kori Ryan, a former criminology student at the California State University, Fresno who delved into the "evolutionary history" of this tantalizing construct for her as-yet unpublished master's thesis. Her ultimate conclusion:

Even though the literature on violent behavior contains many references to the Macdonald triad (and its aliases), collectively these studies do not provide sufficient evidence of its ability to predict violence, nor, in fact, of its existence as a bona fide phenomenon.

Instead, childhood enuresis, firesetting and animal cruelty more likely represent three among many indicators of severe childhood abuse. In other words, the presence of one or more of these elements in the histories of some violent offenders can be explained by the fact that violent offenders are often the products of child abuse. More importantly, relying upon these behaviors as predictors of future violence would lead to many false positives, punishing children who might not be violent in the future.

One of many misleading websites

Roots of the legend 

Gulliver's Travels

Forensic psychiatrist John Macdonald is generally credited with "discovering" the triad. In a 1963 article in the American Journal of Psychiatry, entitled "The Threat to Kill," he gave his clinical impression that "a history of great parental brutality, extreme maternal seduction, or the triad of childhood firesetting, cruelty to animals and enuresis" can signal those who will eventually threaten homicide. His article was based on his work with 100 patients at the Colorado Psychopathic Hospital in Denver, Colorado who had threatened -- but not necessarily committed -- violence. 

Over the next few decades, the idea "attracted a dedicated following" and gradually expanded to encompass various forensic groups, including sexual sadists, recidivist firesetters and -- most salacious -- serial killers.

Ryan traces the history of cultural interest in these behaviors all the way back to Greek mythology and early Western fiction, such as Jonathan Swift's 1726 Gulliver's Travels, in which Gulliver puts out a fire with his own urine, much to the chagrin of the Imperial Majesty, thereby linking urination with fire and revenge.

Early psychoanalytic thinkers also placed heavy emphasis on these behaviors, seeing them as products of arrested psychosexual development and sublimated sexual and sadistic urges. Psychoanalyst Melanie Klein, for example, saw bedwetting as a daughter’s sadistic revenge against her mother.

Empirical research: Triad goes bust

Two psychiatrists were the first to empirically evaluate the Macdonald triad, according to Ryan. Studying 84 incarcerated offenders in 1966, Hellman and Blackman reported a positive association between the triad and future violence. Accordingly, some took to labeling the phenomenon as the “"Hellman and Blackman triad."

But subsequent attempts to replicate Hellman and Blackman's findings were unsuccessful. Even John Macdonald himself voiced later doubt about the triad's validity. After trying to test his own clinical theory, Macdonald reported in his 1968 book, Homicidal Threats, that he could find no statistically significant association between homicide perpetrators and early problems with firesetting, cruelty to animals, or enuresis.

Likewise, in an examination of 206 sex offenders at the Massachusetts Treatment Center for Sexual Dangerous Persons, Prentky and Carter (1984) found "no compelling evidence" for the idea that the triad predicted adult criminality. They did, however, note that the individual components of the triad were common among people raised in highly abusive home environments.

Some years later, this was also the conclusion of Jonathan Pincus, in his 2001 book on convicted murderers. Pincus described "a forensic assessment protocol in which bed-wetting, firesetting, and cruelty to animals (among other behaviors) are considered 'hallmarks' of childhood abuse," notes Ryan.

Indeed, it seems far more likely that one of Macdonald’s five original indicators that didn’t go on to fame has more explanatory power as a cause of later violence: parental brutality.

Dangerous ramifications

"The frequency with which discussions of violent offenders (of various types) include mention of the Macdonald triad suggests its general acceptance as a predictor of violent behavior," notes Ryan.

This continuing prominence owes in large part to the triad's promotion by prominent FBI profilers in the 1988 book, Sexual Homicide: Patterns and Motives. Like Macdonald’s, the FBI study was anecdotal, small-scale and lacking in any statistical analyses or control groups. Studying 36 sex killers, Douglas, Burgess and Ressler found that many manifested one or more elements of the triad. Unfortunately, notes Ryan, the authors did not report which factors were present in which subjects, or how many of these killers evidenced all three components of the triad.

Ryan warns that promotion of the triad has real-world ramifications, in that children who exhibit one or more of these behaviors "might be falsely labeled as potentially dangerous."

For example, police officers exposed to the triad in undergraduate criminology courses may target young offenders who have lit a fire or harmed an animal -- both fairly common behaviors among troubled youth -- as future sex fiends or serial killers. (Enuresis, with less face validity as an indicator of sadism, has tended to drop from more contemporary renditions of the triad.)

Ignoring the miniscule base rate of serial killers, even veterinarians are encouraged to identify those who hurt pet animals as potentially lethal: "Many known serial killers began their careers by hurting pet animals," warn the authors of a 2004 article in one veterinary journal. "It is well known in the criminology field that people who perpetrate acts of cruelty on animals, frequently escalate to torturing humans, usually the young and helpless."

Rather than throwing the baby out with the bathwater, Ryan says researchers could do more research to understand these behaviors in context. For example, might arson be a coping mechanism in children who have experienced severe emotional abuse, rather than a marker for future aggression? Are some elements of the triad indicators for future violence when they co-occur? More fundamentally, is there any set of behaviors that can legitimately be considered a behavioral syndrome predictive of later violence?

The study is: The Macdonald triad: Predictor of violence or urban myth? The abstract is HERE; the full text can be requested from the author via ResearchGate (HERE). The author, Kori Ryan, can be contacted HERE.*

*Links updated 12/1/16.