This thesis tests one of the major propositions of deterrence theory: that increases in the severity of punishment can reduce the likelihood of offending. To this end, a case study in which the statutory penalties were doubled for almost all drink-driving offences in New South Wales, Australia, is examined. Two quasi-experimental studies were undertaken to assess the impact of these legislative changes: an interrupted time-series analysis of road crash rates (Study 1) and an analysis of drink-driving reoffending rates before and after the penalty changes were implemented (Study 2). Study 1 showed a significant increase in a surrogate measure of alcohol-related road crashes after the tougher drink-driving penalties were introduced. Further analyses suggested that this increase was driven primarily by a secular rise in non alcohol-related crashes that coincided with the policy???s implementation. Two possible conclusions about the deterrent effect of the policy are drawn from these findings: (1) that there was a reduction in alcohol-related road crashes which was overwhelmed by the rise in non alcohol-related crashes occurring around the same time or (2) that there was no change in crash rates. Study 2 found that drink-drivers who were convicted under the new penalty regime were less likely, and took longer, to reoffend than drink-drivers convicted before the introduction of the new penalties. This reduction in reoffending was only apparent for drink-drivers residing in country and regional areas and was small in magnitude.These latter findings are consistent with the possibility that the penalty changes coincided with a reduction in alcohol-related crashes but suggest that any decrease is likely to have been relatively small. A third study using a scenario-based survey methodology was also undertaken to examine the relationship between legal sanctions and willingness to drink-drive, controlling for other factors. The results of this study showed that participants who were more knowledgeable about drink-driving penalties were less likely to state that they would offend in the drink-driving scenario than participants who were less knowledgeable about the law. The implications of these findings for deterrence theory and criminal justice policy are discussed.

This thesis tests one of the major propositions of deterrence theory: that increases in the severity of punishment can reduce the likelihood of offending. To this end, a case study in which the statutory penalties were doubled for almost all drink-driving offences in New South Wales, Australia, is examined. Two quasi-experimental studies were undertaken to assess the impact of these legislative changes: an interrupted time-series analysis of road crash rates (Study 1) and an analysis of drink-driving reoffending rates before and after the penalty changes were implemented (Study 2). Study 1 showed a significant increase in a surrogate measure of alcohol-related road crashes after the tougher drink-driving penalties were introduced. Further analyses suggested that this increase was driven primarily by a secular rise in non alcohol-related crashes that coincided with the policy???s implementation. Two possible conclusions about the deterrent effect of the policy are drawn from these findings: (1) that there was a reduction in alcohol-related road crashes which was overwhelmed by the rise in non alcohol-related crashes occurring around the same time or (2) that there was no change in crash rates. Study 2 found that drink-drivers who were convicted under the new penalty regime were less likely, and took longer, to reoffend than drink-drivers convicted before the introduction of the new penalties. This reduction in reoffending was only apparent for drink-drivers residing in country and regional areas and was small in magnitude.These latter findings are consistent with the possibility that the penalty changes coincided with a reduction in alcohol-related crashes but suggest that any decrease is likely to have been relatively small. A third study using a scenario-based survey methodology was also undertaken to examine the relationship between legal sanctions and willingness to drink-drive, controlling for other factors. The results of this study showed that participants who were more knowledgeable about drink-driving penalties were less likely to state that they would offend in the drink-driving scenario than participants who were less knowledgeable about the law. The implications of these findings for deterrence theory and criminal justice policy are discussed.