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.
In Singer and Hensley (2004), firesetting is theorized to be a less severe or first shot at releasing aggression. Extensive periods of humiliation have been found to be present in the childhoods of several adult serial killers. These repetitive episodes of humiliation can lead to feelings of frustration and anger, which need to somehow be released in order to return to a normal state of self-worth. However, the triad combination has been questioned in this regard also, and a review has suggested that this behavior is just one that can occur in the context of childhood antisocial behavior and isn't necessarily predictive of later violence.
Animal cruelty 
FBI Special Agent Alan Brantly believed that some offenders kill animals as a rehearsal for killing human victims. Animal cruelty is mainly used to vent frustration and anger the same way firesetting is. Extensive amounts of humiliation were also found in the childhoods of children who engaged in acts of animal cruelty. During childhood, serial killers could not retaliate towards those who caused them humiliation, so they chose animals because they [animals] were viewed as weak and vulnerable. Future victim selection is already in the process at a young age. Studies have found that those who engaged in childhood acts of animal cruelty used the same method of killing on their human victims as they did on their animal victims.
Wright and Hensley (2003) named three recurring themes in their study of five cases of serial murderers: As children, they vented their frustrations because the person causing them anger or humiliation was too powerful to take down; they felt as if they regained some control and power over their lives through the torture and killing of the animals; they gained the power and control they needed to cause pain and suffering of a weaker, more vulnerable animal – escalating to humans in the future.
In a study of 45 male prison inmates who were deemed violent offenders, McClellan (2003) found that 56% admitted to having committed acts of violence against animals. It was also found that children who abused animals were more often the victims of parental abuse than children who did not abuse animals. As previously stated, animal cruelty was a way for the children to feel as if they were retaliating against those who abused, frustrated, or humiliated them.
However, Tallichet and Hensley (2004) say that studies have been uncertain in regard to animal cruelty and later violence against humans. In their study, which considered not one-off events but patterns of repeat violence, Tallichet and Hensley did find a link between animal cruelty and violence against humans. They examined prisoners in maximum or medium security prisons. The information is useful, but at the same time, more quality information is needed to come to a concrete conclusion. Furthermore, over-generalizing possible links between animal violence and human violence can have unwanted consequences such as detracting focus from other possible predictors or causes.
The idea that bedwetting has anything to do with psychological maladjustment, and certainly with later antisocial or violent tendencies, or plays some part in a triad of predictors, has been described as a destructive myth entirely discredited. Crime researchers acknowledge that it is not linked with later sociopathic behavior. It is not even clear that it is necessarily associated with distress.
However, some authors continue to speculate that enuresis may be related to firesetting and animal cruelty in some way. One argument is that because persistent bed-wetting beyond the age of five can be humiliating for a child, especially if he or she is belittled by a parental figure or other adult as a result, this could cause the child to use firesetting or cruelty to animals as an outlet for his or her frustration. Enuresis is an "unconscious, involuntary, and nonviolent act and therefore linking it to violent crime is more problematic than doing so with animal cruelty or firesetting".
See also 
- Macdonald, JM (1963). "The threat to kill". Am J Psychiatry 120: 125–130. doi:10.1176/appi.ajp.120.2.125.
- Singer, S.D.; Hensley, C. (2004). "Learning theory to childhood and adolescent firesetting: Can it lead to serial murder.". International Journal of Offender Therapy and Comparative Criminology 48 (4): 461–476. doi:10.1177/0306624X04265087. PMID 15245657.
- Montaldo C (recent). Profile of Richard Kuklinski: The Iceman. About.com, viewed 2009-11-14.
- Biography.com staff (recent). Dennis Rader biography. Biography.com, viewed 2009-11-14.
- Dicanio, Margaret (2004). Encyclopedia of Violence. iUniverse. ISBN 0-595-31652-2.
- Skrapec, C. and Ryan, K. , 2010-11-16 "The Macdonald Triad: Persistence of an Urban Legend" Paper presented at the annual meeting of the ASC Annual Meeting, San Francisco Marriott, San Francisco, California
- Firesetting as a predictor of violence Bushfire arson bulletin no. 36 ISSN 1832-2743 Canberra: Australian Institute of Criminology, September 2006
- Barnard, N.D & Hogan, A.R. (1999 June 6). Moving up the chain of abuse pattern shows cruelty to animals is one predictor of violent behavior in adults. Seattle Post-Intelligencer, p. C.1.
- Wright, J.; Hensley, C. (2003). "From animal cruelty to serial murder: Applying the graduation hypothesis". International Journal of Offender Therapy and Comparative Criminology 47 (1): 71–88. doi:10.1177/0306624X02239276. PMID 12613433.
- Wright, Jeremy; Hensley, Christopher (1 February 2003). "From Animal Cruelty to Serial Murder: Applying the Graduation Hypothesis". International Journal of Offender Therapy and Comparative Criminology 47 (1): 71–88. doi:10.1177/0306624X02239276. PMID 12613433.
- McClellan, J. (2007). Animal cruelty and violent behavior: Is there a connection? Journal of Security Education. 2.
- Tallichet, S. E.; Hensley, C. (1 September 2004). "Exploring the Link between Recurrent Acts of Childhood and Adolescent Animal Cruelty and Subsequent Violent Crime". Criminal Justice Review 29 (2): 304–316. doi:10.1177/073401680402900203.
- Patterson-Kane, Emily G.; Piper, Heather (1 September 2009). "Animal Abuse as a Sentinel for Human Violence: A Critique". Journal of Social Issues 65 (3): 589–614. doi:10.1111/j.1540-4560.2009.01615.x.
- Serial Murderers and Their Victims. (E W Hickey). Belmont, CA: Wadsworth Cengage Learning (2009) (page 101).
- Myths about bedwetting: What the research really says 2010 Gwen Dewar, Ph.D.
- Weatherby, G. A.; Buller, D. M.; McGinnis, K. (2009). "The Buller-McGinnis model of serial-homicidal behavior: An integrated approach". Journal of Criminology and Criminal Justice Research and Education 3: 1.
- Hickey, Eric (2010). Serial Murderers and their Victims. Belmont, CA: Wadsworth, Cengage Learning. p. 101. ISBN 978-4-9560081-4-3.