Gary Mauser; Papers and Presentations

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A Brief Summary of Research on Prison and Violent Crime

4 October 2006
Presented to The Standing Committee on Justice and Human Rights,
The House of Commons, Ottawa, Ontario, Canada

Thank you very much, Mr. Chairman.

I am Gary Mauser, a professor at Simon Fraser University. I am privileged to be in both the Institute for Canadian Urban Research Studies in Criminology and the Faculty of Business Administration. I have researched and published in criminology for more than 15 years. My doctoral training was in social psychology and quantitative methods. And my academic research has been published in criminology, political science as well as business journals.

My remarks are directed to the question of whether or not incarcerating serious or violent offenders is effective in protecting the public. My reading of the criminological research suggests that imprisoning serious offenders is indeed effective, that increasing the number of offenders who are incarcerated acts to reduce violent crime rates. This effect is especially pronounced with homicide rates.

The research supports the wisdom of imprisoning those who have been convicted of serious offences, that is, those punishable by prison terms of 10 years or longer.

Some Canadians have a bias against anything American. But to reject American research studies, simply because they are American, runs the risk of ignoring potentially effective solutions to serious Canadian problems. Thus, I believe responsible Canadians should examine US justice policies in order to emulate their successes and avoid their failures. The US, being so much larger, simply has a wider and deeper bank of information from which we can learn.

The facts indicate that violent crime rates have fallen faster in the US than they have in Canada. Between 1992 and 2004, for example, the overall violent crime rate fell 38% in the US, but only 13% in Canada. This precipitous drop is even more evident in homicide rates. During the same time period, the homicide rate in the US fell by 41%, while in Canada it fell only 26%. Please see the attached charts.

Criminologists have been studying this drop, which was unexpected, with some attention over the past decade. The results of this attention are now becoming clearer. There are literally hundreds of studies. I will limit my discussion to the most important ones.

Especially illuminating is the research conducted by Marvel and Moody who are among the most respected criminologists in the world. In their time-series studies, they found strong results at the national level affirming that expanding prison populations is convincingly tied to reducing violent crime rates.

Marvel and Moody's (1997) research demonstrates that for every 10% increase in prison population, homicide rates drop by 13%. In their studies, they controlled for a wide range of other variables; such as, inflation, unemployment, demographic trends and other socio-economic factors.

They found similar, but weaker, relationships for assault and robbery. They speculate that this weaker statistical relationship is most likely due to the lower quality of arrest data for crimes other than homicide.

Marvel and Moody's results were quite robust, and their research findings have been replicated by other researchers. One study in particular, by Kovandzic and his colleagues (2004), deserves mention. They not only confirmed Marvel and Moody's earlier findings, but they also examined the effect on violent crime rates when offenders got out of prison. They found that there was no evidence of a significant positive relationship between prison releases and homicide.

Many researchers have observed that prisons are expensive. That is true. However, who ultimately bears the cost of crime is a question of more importance than the cost itself. Yes, prison costs taxpayers more than does probation or house arrest. But the costs of criminal violence are paid by the victims; the lives blighted; the lives of husbands, wives, and children lost to criminal violence.

When serious offenders are allowed to escape serious jail time, they are then free to commit more violent crimes. Individual Canadians bear these costs. To take only one example: Jane Creba, who was killed in Toronto on Boxing Day last year, might still be alive had the previous government acted to keep serious offenders in jail longer (Pazzano 2006). Other examples of questionable sentencing decisions are frequently reported in the media. (See media reports below).

Research in both the US and in Canada suggests that those in social minorities are victims of violent crime at higher rates than are other citizens. Thus, it follows that increased prison terms will be especially effective in reducing the victimization rates among minority members. In Canada, aboriginal victims disproportionately bear the costs of violent crime; thus, aboriginal people will be among the primary beneficiaries of a program that incarcerates serious offenders.

Before I conclude I would like to say a few words about the tendency of many people to refuse to believe statistical studies that do not conform to their previous beliefs. Such a position is buttressed by the cynical claim that statisticians can obtain any result that they wish simply by massaging the data. Such cynicism justifies laziness and ignorance. Certainly liars and sophists use statistics. Liars misuse words, too, but that does not mean we should give up on language.

In conclusion, despite what you may hear from special interest groups who cherry-pick their data, the criminological research is quite clear: longer prison terms for serious or violent offenders have been important in the dramatic fall in violent crime in the US. These results support the logic behind Bill C-9, that of incarcerating those who have been convicted of serious offences, that is, punishable by prison terms of 10 years or longer.

Thank you for your attention. I will be glad to answer questions.

Professor Gary Mauser

Institute for Canadian Urban Research Studies in Criminology
Faculty of Business Administration
Simon Fraser University


  • Cohen L.E. and K.C. Land. Age structure and crime: symmetry vs. asymmetry and the projection of crime rates through the 1990s. American Sociological Review, Vol. 52, pp 170-183, 1987
  • Dauvergne, Mia. "Homicide in Canada, 2004." Juristat, Vol 25, No 6. Statistics Canada, Ottawa, Ont, 2005.
  • Federal Bureau of Investigation, UCR Reports, Index of Crime, Table 1. Source:
  • Kaminski R.J. and T.B. Marvell. A comparison of changes in police and general homicides, 1930-1998, Criminology, Vol. 40, pp 171-189, 2002
  • Kessler, Daniel and Steven Levitt. Using sentence enhancements to distinguish between deterrence and incapacitation, Journal of Law and Economics, Vol. 42, April, 1999, p. 343-363
  • Kovandzic, T.V., T.B. Marvel, L.N. Vieraitis, and C.E. Moody. When prisoners get out: the impact of prison releases on homicide rates, 1975-1999 Criminal Justice Policy Research, Vol. 15, pp 212-228, 2004
  • Levitt, Stephen. Understanding why crime fell in the 1990s. Journal of Economic Perspectives, Vol. 18-1. Winter, 2004
  • Marvell, T.B. and C.E. Moody. Female and male homicide victimization rates: Comparing trends and regressors, Criminology, Vol. 37, pp 879-902, 1999

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