The Macdonald triad (also known as the triad of sociopathy or the homicidal triad) is a set of three factors, the presence of any two of which are considered to be predictive of, or associated with, violent tendencies, particularly with relation to serial offenses. The triad was first proposed by psychiatrist J. M. Macdonald in “The Threat to Kill”, a 1963 article in the American Journal of Psychiatry. Small-scale studies conducted by psychiatrists Daniel Hellman and Nathan Blackman, and then FBI agents John E. Douglas and Robert K. Ressler along with Dr. Ann Burgess, claimed substantial evidence for the association of these childhood patterns with later predatory behavior. Although it remains an influential and widely taught theory, subsequent research has generally not validated this line of thinking.
The triad links cruelty to animals, obsession with fire-setting, and persistent bedwetting past a certain age, to violent behaviors, particularly homicidal behavior and sexually predatory behavior. However, other studies claim to have not found statistically significant links between the triad and violent offenders.
Further studies have suggested that these behaviors are actually more linked to childhood experience of parental neglect, brutality or abuse. Some argue this in turn results in “homicidal proneness”. The “triad” concept as a particular combination of behaviors linked to violence may not have any particular validity – it has been called an urban legend.