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Mass Murder as Quasi-Experiment: The Impact of the 1996 Port Arthur Massacre

NCJ Number
195589
Journal
Homicide Studies Volume: 6 Issue: 2 Dated: May 2002 Pages: 109-127
Author(s)
Carlos Carcach; Jenny Mouzos; Peter Grabosky
Date Published
May 2002
Length
19 pages
Annotation
Using a disaggregation strategy and intervention analysis, this paper examines the impact of Australia's Port Arthur massacre (35 people murdered) on subsequent homicides in Australia.
Abstract
For the purposes of this paper, "mass murder" is defined as "the willful killing of four or more individuals during the same incident, lasting but a few minutes or as long as several hours." On April 28, 1996, a lone gunman opened fire and killed 35 people at Port Arthur in the Australian island-state of Tasmania. The current study explored whether this massacre had an impact on Australian homicides and on those types of homicides most similar to the Port Arthur killings, i.e., firearm homicides in which the victim and offender are strangers. Data were obtained from the National Homicide Monitoring Program at the Australian Institute of Criminology. Established in 1990, this program routinely collects data that relate to each incident of homicide coming to police attention in Australia. The data encompass victim and offender characteristics, as well as the setting or context within which the incident occurred. The analysis was conducted on data over three time periods of different length. The first period covered all homicides that occurred between July 1, 1989, and April 27, 1996, the day before the Port Arthur massacre. The second period covered all homicides that occurred between April 29 and May 4, 1996, the period immediately after the Port Arthur massacre, when levels of media coverage were highest. The third period covered all homicides that occurred between May 5, 1996, and June 30, 1999, the period during which the new firearms reforms were introduced and implemented. Findings indicate that the Port Arthur incident apparently had no lasting effect on homicide patterns in Australia; however, there was an immediate increase in firearm homicides during the 5 days following the massacre. After this sudden increase, the incidence of homicide resumed its long-term downward trend. This sudden increase in homicides can be interpreted as evidence of a contagion effect, with the significant response by the Australian Government contributing to the incidence of homicide resuming its long-term trend, rather than continuing to increase. 10 tables, 1 figure, and 28 references