Predicting a Killer: The MacDonald Triad (Myth)

From the evening news, the podcast Serial, to the documentary Making a Murder on Netflix, fascination with homicide continues to grow over the decades. Part of the interest stems not just from the crimes committed, but looking into the history of the person committing the crime and determining what drove them to commit the heinous act. Through various portrayals of what leads one to engage in such violent crime, it is not surprising that there are also associated distortions and myths.

A common phenomenon that is often referenced even today to explain predictors of violence was established by John M. MacDonald. In 1963, he published an article, The Threat to Kill, in which he discussed that in addition to “a history of great parental brutality, extreme maternal seduction,” there were also three behaviors exhibited during childhood that were predictive factors in subsequent violent behavior, especially when two or more are present. These behaviors included extreme cruelty to animals, fire setting, and enuresis (i.e., involuntary urination / ‘bedwetting’) and are now known as the MacDonald Triad, homicidal triad, or the Hellman and Blackman triad. Over time, the MacDonald Triad received great attention in the field of forensics and psychology, being taught in universities and showing up in popular TV series. However, is this triad truly a predictor of violence, or a myth? To better understand and determine whether there is validity of this phenomenon, Kori Ryan of California State University explored it further. In his 2009 publication, The Macdonald Triad: Predictor of Violence or Urban Myth, Ryan examined the origins and evolution of the triad. According to his findings, there is limited empirical support for the MacDonald triad. Nonetheless, while the triad may not predict what it was said to predict in 1963, it is important to note whether each behavior alone may have some value when considering its impact on violent behavior.

Looking at enuresis independently as a predictor of future violence or psychopathy, there is very little empirical support. The research available is determined to either be outdated, the sample size studied too small and under representative of the general population, or the research design utilized was deemed to be poor. In regard to animal cruelty and fire-setting, research has not developed a clear link between these behaviors and future violent behaviors, but it has helped shed light on characteristics of a person who engages in such behaviors. For instance, in 2007 a study called Cruelty to Animals and Violence to People published by Marie Louise Petersen and David P. Farrington found evidence that children who are cruel to animals tend to be disproportionately violent towards people later in life, and that animal cruelty tends to be associated with domestic violence, child abuse, and elder abuse. In 2016, Glenn D. Walters found that animal cruelty may serve as a marker for fearlessness and callous-unemotional traits, whereas fire-setting may serve as a marker for disinhibition and low self-control. These identified characteristics may be found amongst individuals engaging in violent behaviors, such as homicide as adults, but the acts of animal cruelty and fire-setting alone are not indicated as predictors of homicide.

The misconception these childhood behaviors predict adult violence has resulted in it becoming common children who display cruelty to animals, engage in fire setting behaviors, and/or suffer from enuresis are assumed to be at risk to grow up and develop violent tendencies or even become serial killers. Continuing to support this triad, which has not been borne out by the research, can have negative consequences in that children may be prematurely labeled as dangerous for exhibiting one of the three behaviors that create the triad. While thankfully most people no longer think of enuresis as a risk factor for future violence, fire setting is still erroneously believed by much of the public to increase risk of extreme violence in adulthood. Of the three, cruelty to animals is the most predictive of violence later in life. Children who engage in fire setting or cruelty to animals should be treated with professional psychological help. Bed wetting may suggest a need for psychological help for some, but is best addressed initially as a medical condition. As noted in a 2012 Psychology Today article, “Together or alone, the triad behaviors can indicate a stressed child with poor coping mechanisms; such a child needs guidance and attention. However, until we design and carry out better empirical studies than we’ve seen thus far, researchers and media agencies should refrain from stating that the triad identifies a future serial killer.”