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4513.0 - Criminal Courts, Australia, 2001-02  
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 09/04/2003   
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NATIONAL OFFENCE INDEX - TECHNICAL PAPER


INTRODUCTION

1 In the 2000-01 Higher Criminal Courts publication, the National Criminal Courts Statistics Unit (NCCSU) developed and applied a set of national counting rules to produce principal offence information for adjudicated defendants. These rules were developed to overcome the different practices in the states and territories associated with recording offences and /or identifying a single offence to report against a defendant.

2 Principal offence information for adjudicated defendants was published in experimental tables in the appendixes of the 2000-01 publication. However, there were several issues that arose from the application of these rules.

  • They were complex and difficult to apply, with some data providers unable to apply the rules to their own data
  • They resulted in an unsatisfactory proportion of defendants for which the principal offence was unable to be determined (up to 30%)
  • There was greater scope for error in the determination of the principal offence due to the complex nature of the rules and the reliance on at least three different data items (offence, penalty type and penalty quantum)
  • They cannot be applied to police/crime data as the rules are based on actual penalties handed down at a criminal court sentence hearing.

3 As part of the quality improvement processes for the representation of offence information in crime and justice collections, the National Centre for Crime and Justice Statistics (NCCJS) has developed a National Offence Index (NOI). The NOI is a ranking of offence categories of the Australian Standard Offence Classification (ASOC) according to their level of seriousness. The ASOC was used to ensure that offence statistics were reported according to a standard classification. This overcomes different ways of categorising offence information across the states and territories reflecting their different legislative frameworks.

4 The purpose of the NOI is to enable the representation of a defendant by a single offence. Therefore, where a defendant has two or more offences in different output offence categories (for this publication the output offence category is the ASOC division) the most serious offence is chosen to represent that defendant. For the purposes of this publication, categorisation by a single principal offence provides an important and useful way of understanding the types of criminal cases finalised in the Magistrates' and Higher Criminal Courts. It also provides a mechanism for associating offence information with a range of data variables linked to the defendant.


NATIONAL OFFENCE INDEX (NOI) DEVELOPMENT

5 The NOI is based on the Offence Seriousness Index developed by the Crime Research Centre (CRC) in Western Australia. The CRC Index was developed using two methodologies: research on public perception of offence seriousness and consideration of legislated sentences. The Index was developed in 1991, and subsequently reviewed in 1998 following the introduction of the ASOC. The review in 1998 ranked all ASOC groups (4 digit codes), though no supplementary codes were included. The ABS has used the 1998 version of the CRC Index as a base Index for the NOI.

6 Evaluation of the CRC Index was conducted utilising data from the ABS' Higher Criminal Courts collection for the period 1 July 2000 to 30 June 2001. Data on the most serious offence using the CRC Index was compared with the ABS' principal offence data from this collection. All adjudicated offences were mapped to the ASOC. The Principal Offence Rules determined principal offence based on severity of sentences handed down to defendants (sentence type followed by sentence quantum).

7 The results indicated that the output from the two methods were similar, with the most notable differences occurring in the ASOC divisions: 2-Acts intended to cause injury; 6-Robbery, extortion and related offences; 7-Unlawful entry with intent; 8-Theft and related offences; and, 10-Illicit drug and related offences. Also, the proportion of defendants for whom principal offence could not be determined, although lower than that using the principal offence rules (national average of 17%), was still quite high (national average of 12%). The main explanation for the figure of 12% was that offence information in the Higher Criminal Courts collection included supplementary ASOC codes (i.e. division and subdivision codes). These codes were not included in the CRC Index and therefore were unable to be ranked and subsequently the defendant was unable to be allocated a principal offence.

8 The analyses above indicated two key areas to be investigated further:
  • the investigation of the ASOC divisions which showed the greatest differences between the two methods
  • the possible inclusion of supplementary codes into the Index.

9 An analysis of co-occurring ASOC divisions was conducted. This analysis indicated that the ASOC divisions most likely to co-occur were the same ASOC divisions indicated in paragraph 7 above. Therefore, for offences that most often co-occur it is more likely that there will be differences in their selection as a principal offence using the Principal Offence Rules versus the CRC Index. Following this analysis and consultation with the practitioner and advisory groups in crime, courts and corrections, changes were made to the ranking of selected offences. These changes were:
  • specific placement of aggravated robbery (ASOC group 0611) above aggravated assault (ASOC group 0211)
  • specific placement of theft from a person (ASOC group 0821) above theft of motor vehicle parts/contents (ASOC group 0813)
  • general placement of sexual and related offences (ASOC division 3) above illicit drug and related offences (ASOC division 10)
  • general placement of deception and related offences (ASOC division 9) above theft and related offences (ASOC division 8).

10 Separate analysis of the offence data in the Higher Criminal Courts collection for 2000-01 indicated that around 10% of all adjudicated offences for adjudicated defendants had supplementary ASOC codes that were not included in the CRC Index. In developing the NOI, these ASOC codes were allocated an Index ranking where possible. There were three scenarios for this:
  • Where all the offences at the same division level were grouped together in the NOI it was possible to insert the division code below these group level codes (i.e. keep all the offences in the same division together);
  • Where all the offences at the same subdivision level were grouped together in the NOI it was possible to insert the subdivision code below these group level codes (i.e. keep all the offences in the same subdivision together); or
  • Where ASOC groups in the same ASOC subdivision or division were not grouped together the insertion of relevant ASOC division or subdivision codes was considered on a case-by-case basis in consultation with the practitioner and advisory groups, taking into account the types of offences that separate the relevant ASOC codes and whether they are likely to co-occur with the subdivision and/or division codes that are being considered.

11 The inclusion of selected ASOC supplementary codes reduced the national proportion of adjudicated offences for adjudicated defendants unable to be ranked from around 10% to less than 2%.

12 The NOI was used to produce principal offence output from the 2000-01 Higher Criminal Courts collection, which was then compared with the principal offence output produced using the Principal Offence Rules. The analysis indicated:
  • the proportion of adjudicated defendants for whom a principal offence was unable to be determined reduced from a national average of 17% to 3% using the NOI
  • the distribution of offences using the NOI is similar to that produced using the Principal Offence Rules and as included in the experimental tables in the ABS' Higher Criminal Courts publication for 2000-01.

13 The application of the NOI is simple compared with the Principal Offence Rules as the NOI only requires valid ASOC codes, whilst the Principal Offence Rules require valid ASOC codes, sentence type and sentence quantum. In addition, the NOI is more robust because it deals with situations such as global sentencing (a single sentence given for multiple offences), which has a large impact on the output in some States and Territories. Added to this, there is scope for greater usage due to decreased burden on data providers, and usage can extend across police, courts and corrections agencies as the NOI does not require sentencing information.


APPLICATION OF THE NATIONAL OFFENCE INDEX

14 The NOI has been used to produce the principal offence information in this publication for the defendants finalised by adjudication in the Higher Criminal Courts and Magistrates' Criminal Courts.

15 The NOI is only applied to adjudicated offences for adjudicated defendants - i.e.those proven guilty [Guilty verdict/Guilty plea] or acquitted - and is determined according to the following rules:
  • Where a defendant has one adjudicated offence, that offence is the principal offence (the NOI does not need to be applied).
  • Where a defendant has multiple offences with some adjudicated as guilty and some acquitted, offences proven guilty take precedence over offences acquitted.
  • If there is one offence adjudicated as guilty, that offence is the principal offence for the defendant (the NOI does not need to be applied).
  • Where there are multiple offences adjudicated as guilty, apply the NOI to those offences to determine the principal offence for the defendant.
  • Where multiple offences are all adjudicated as acquitted, apply the NOI to determine the principal offence for the defendant.


CONSIDERATIONS WHEN USING THE NATIONAL OFFENCE INDEX (NOI)

16 The assumptions and rules underpinning the NOI, in particular, defining 'offence seriousness' and the subsequent impact of this definition on the ranking of offences, need to be kept in mind when using the principal offence data in this publication. However, it is important to note that these technical issues are only of practical significance where a choice must be made between output categories, which for this publication are the ASOC divisions (see Appendix 4 in the publication). For example, although some sexual and related offences are ranked ahead of drug and related offences, they are unlikely to co-occur.

17 For defendants adjudicated in the Higher Criminal Courts and Magistrates' Criminal Courts in Australia, the majority of these defendants have one offence adjudicated, or offences within the one ASOC division (69%). Therefore, these defendants do not require the application of the NOI.

18 The application of the NOI is currently being investigated further for the ABS Prisoners in Australia collection and collections currently under development. Therefore, the Index may change over time.


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