Macdonald Triad

The Macdonald triad (also known as the triad of sociopathy) is a set of three behavioral characteristics that were originally claimed, if present together, to be associated with later violent tendencies. The triad was first proposed by J.M. Macdonald in "The Threat to Kill", a 1963 paper in the American Journal of Psychiatry.

The triad links animal cruelty, obsession with fire setting, and persistent bedwetting past the age of five to violent behaviors, particularly homicidal behavior. However, other studies have not found statistically significant links between the triad and violent offenders. Nevertheless, some serial killers exhibited at least some of these behaviors during childhood. For example, contract killer Richard Kuklinski, serial killer Dennis Rader, serial killer Richard Chase and serial killer Gary Ridgway all engaged in acts of animal cruelty.

Further studies have suggested that these behaviors are often the product of parental neglect, cruelty or trauma, and that such events in a person's childhood can result in "homicidal proneness". However, the 'triad' concept as a particular combination of behaviors may not have any particular validity - it has been called an urban legend.