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The effect of arrest and imprisonment on crime

 

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Release date: Tuesday, 13 March 2012 Embargo: 10.30am

Increasing the risk of arrest and the probability of imprisonment are much more effective in preventing property and violent crime than increasing the length of prison terms, according to a new study of the effectiveness of the criminal justice system in controlling crime, released today by the NSW Bureau of Crime Statistics and Research.

The study is one of the most comprehensive ever carried out in Australia into the effectiveness of the criminal justice system in controlling crime.

It examined the effect of changes in the probability of arrest, the probability of imprisonment and the length of the average prison term on trends in property and violent crime across every Local Government Area (LGA) in NSW between 1996 and 2008.

Special measures were taken to control for other factors that influence crime, such as household income and drug use. The study also controlled for the effect of crime on the criminal justice system.

The Bureau found that a 10 per cent increase in the risk of arrest in the long run produces a 1.35 per cent reduction in property crime, while a 10 per cent increase in the imprisonment risk produces a 1.15 per cent reduction in property crime.

Similarly, in the long run, a 10 per cent increase in the risk of arrest for violent crime produces a 2.97 per cent reduction in violent crime, while a 10 per cent increase in the risk of imprisonment produces a 1.7 per cent reduction in violent crime.

Although increasing the risk of arrest appears to exert a stronger effect on property and violent crime than increasing the risk of imprisonment, the differences were not found to be statistically significant. Arrest and imprisonment, however, were found to exert significantly stronger effects on violent crime than on property crime.

A 10 per cent increase in the risk of arrest in the long run produces a 2.97 per cent reduction in violent crime, compared with a fall of only 1.35 per cent reduction in property crime.

Similarly, a 10 per cent increase in the imprisonment risk reduces violent crime by 1.7 per cent compared with a 1.2 per cent reduction in property crime.

The stronger effect for violent crime may be at least partly due to the higher risk of arrest for violent crime relative to property crime. The 30 day clear-up rate for non-domestic assault, for example, is 21.7 per cent, compared with 3.7 per cent for burglary.

Interestingly, the study found that household income exerted a much stronger effect on crime than the criminal justice system.

A 10 per cent increase in household income was estimated to produce an 18.9 per cent reduction in property crime over the long term and a 14.6 per cent reduction in violent crime. The effect of income on property crime is more than 14 times larger than the effect of arrest, while its effect on violent crime is nearly five times larger.

Commenting on the findings, the Director of the Bureau, Dr Don Weatherburn, said that they were very reassuring given that Australia currently spends more than $11.5 billion annually on law and order. In per capita terms, this amounts to $511.00 per person per annum.

"At the same time, it is important to bear in mind that the study did not examine the cost-effectiveness of current policy in controlling crime."

"Overseas research suggests that it is possible in some circumstances to cut crime and spend less doing it than we currently spend locking people up. The NSW Drug Court is a good example."

Further enquiries: Dr Don Weatherburn, 9231-9190