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CJB142

Author Ian MacKinnell, Patrizia Poletti and Matthew Holmes
Published August 2010
Report Type Crime and Justice Bulletin No. 142
Subject Statistical methods and modelling
Keywords Median Sentence Ranking (MSR), offence seriousness

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Summary

Aim

To present and assess two new measures of offence seriousness in NSW.

Method

The first measure of offence seriousness, Median Sentence Ranking (MSR), was constructed by identifying the median sentence actually imposed in each Australian Standard Offence Classification (ASOC) group. The data used for this purpose consisted of cases finalised in the NSW Children’s, Local, District and Supreme Courts between 3 April 2000 and 31 March 2005 where the offender had no prior criminal record. The second measure, Median Statutory Maximum Ranking (MSMR), was constructed by reference to the median statutory maximum penalty applicable among offences in each ASOC group. Logistic regression was used to compare the MSR and the MSMR to the current National Offence Index (NOI) in terms of (a) their ability to predict who will be sentenced to imprisonment, and (b) their ability to identify the principal offence, that is, the offence that incurred the most severe penalty.

Results

The MSR proved superior to both the NOI and MSMR both in its ability to predict a sentence of imprisonment and to predict the principal offence. The MSMR proved superior to the NOI in its ability to predict a sentence of imprisonment, however, the NOI proved superior to the MSMR in predicting the principal offence.

Conclusion

The MSR is the better choice when the aim is either to investigate or control for the influence of offence seriousness on the likelihood of imprisonment or to identify which of two offences will incur the more severe sentence. The NOI is a relatively robust measure of seriousness which may make it useful when alternative measures are not available or cannot be derived or when the aim is to predict outcomes outside the criminal justice system where public opinion is a salient factor.

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