Between 1964 and 1973, Edmund “Ed” Kemper brutally murdered 10 people, including his paternal grandparents, mother and his mother’s best friend. The other victims were female college students, whom he abducted and dismembered before performing sex acts on their corpses and hiding their remains in wooded areas. Kemper turned himself over to authorities in April 1973. On November 8 that same year, a jury found the “Co-Ed Killer” guilty of eight counts of first-degree murder. He received eight consecutive life sentences.
From prison, Kemper participated in numerous interviews with psychiatrists and members of law enforcement. He divulged extensive details about his tumultuous childhood and crimes to former FBI special agents John Douglas and Bob Ressler, and Boston College professor Ann Burgess. Among other disturbing behaviors, Kemper confessed to torturing and killing cats as a child and putting their dismembered remains in his closet. Douglas, Ressler and Burgess used the information Kemper provided to build on the “Macdonald triad“—a theory once heavily cited in the profiling of future serial killers.
The Origins and Evolution of the Macdonald Triad
Criminal motivation remained mostly a mystery until 1963, when forensic psychiatrist John Macdonald published a paper titled The Threat to Kill. In addition to a pattern showing “great parental brutality” and “extreme maternal seduction,” Macdonald identified animal cruelty, fire setting and persistent bedwetting (enuresis) in childhood as predictive factors of future aggression and violent behavior in adults, particularly a tendency toward committing homicide or serial murder. The latter three behaviors became the basis of the Macdonald triad (also known as the triad of sociopathy or the homicidal triad).
Macdonald developed his theory based on clinical observations of a small, homogenous group. The subjects included 48 psychotic patients and 52 non-psychotic patients who had threatened to kill someone. None had acted on his or her threats. Macdonald claimed that the most sadistic and aggressive individuals he studied exhibited some form of the three behaviors in childhood.
Overnight, the triad became a major talking point in the fields of forensics and psychology. Researchers, including Douglas, Ressler and Burgess, conducted widely cited follow-up studies that seemed to support the Macdonald triad, especially when two or more behaviors presented. “Folks stuck onto these three behaviors that can happen in childhood. Then the FBI picked up on it, and it kind of took on a life of its own,” Kori Ryan, an assistant professor of behavioral sciences at Fitchburg State University who has studied the Macdonald triad extensively, tells A&E True Crime. “But it turns out that the Macdonald triad was like a game of telephone, a really long game of academic telephone.”
‘Debunked,’ But Still Popular
The Macdonald triad is a mainstay in pop culture and still cited by criminologists. But there is limited empirical support for the Macdonald triad—which Macdonald tried to explain in a follow-up paper refuting his own theory. Of the few, mostly anecdotal independent studies that critically examined Macdonald’s original work, many lacked the science and evidence to definitively support his theory. “People keep debunking it, because it’s one of those things where it makes sense on the outset, but then when you put everything together, there are a few missing pieces,” Judy Ho, a clinical and forensic psychologist, tells A&E True Crime.
Evidence shows that any one of the triad behaviors, when isolated, could be associated with future aggression and serial offenses—including serial murder. But it is rare to find all three behaviors together as predictors. “When you look at individuals who commit crimes, especially serial crimes, you sometimes see these early childhood factors like cruelty to animals and obsession with fire setting,” Ho explains. “These are actually associated with what we commonly define as a psychopath. Or for psychologists, we call it antisocial personality disorder.”
The most strongly correlated with future violence, based on extensive research, is extreme cruelty to animals—not curious kids pulling legs off spiders, but senseless and brutal killing like dismembering family pets. “Cruelty to animals, especially at a very young age—like a five or six-year-old knowing how to decapitate a cat—often shows that there’s something beyond environmental for these children, something biological perhaps like a missing sensitivity chip,” says Ho.
The piece of the Macdonald triad that makes the least sense is persistent bedwetting, a common childhood behavior. “Persistent bedwetting can be really common in boys until they’re much older and it can be related to other issues like ADHD,” says Ryan. “But it doesn’t necessarily mean anything in isolation.”
Together or alone, the triad behaviors can indicate that a child has a dysfunctional home environment, poor coping mechanisms or a developmental disability. It might also mean they are suffering severe trauma from physical, sexual or emotional abuse or neglect. These are more significant risk factors for a child developing into an adult who engages in criminal activity or exhibits violent behavior.
It’s important that concerned parents or caregivers have a child professionally evaluated, Ryan says. “Just because a child exhibits one or more of these behaviors doesn’t mean they’ll grow up to be a serial killer.”
Predicting a Future Serial Killer Could Be Impossible
According to Ryan, while certain behaviors and risk factors can elevate the prospect for violent tendencies, there’s no foolproof way to predict how someone is going to be years down the road. “I would hesitate to say that you could ever spot a serial killer early on… We don’t know as much as we’d like to think we know about serial killers, because there are so few of them. So, it’s a difficult thing to study because of the limited numbers and retrospective analysis involved.”
Ho says such predictions are difficult because there are so many factors to being human. “Even if someone has biological, genetic predispositions, and even if they grew up in a traumatic environment, they could turn their life around well before hitting adulthood,” she explains. “There’s never going to be a 100 percent predictive model—which, of course, is what troubles everyone.”