Explanatory Notes

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Explanatory notes provide information on the methodology underpinning the production of Western Australia (WA) crime statistics.

Introduction

From July 2017, the crime statistics published on the WA Police Force website are derived from ‘Recorded Offences’. These are criminal offences which are reported to police, or become known to police within the relevant time period where a criminal offence occurred.

Prior to this date the WA Police Force reported on ‘Verified Offences’, see Table 2 for more detail.

From July 2017, the calculation of the ‘Sanction Rate’ has been updated to reflect these changes, see Sanction Rate section for more detail.

Due to ongoing police investigations, offence counts are subject to revision until incidents are finalised.

Data source

Offence statistics are derived from information held in administrative systems maintained by the WA Police Force.

Reference period

Offence statistics are produced quarterly with release in the last week of the subsequent month following the end of the quarter.

Scope

The scope of the collection includes selected criminal offences that have been recorded by the WA Police Force during the reference period for the State of Western Australia.

The selected offences are presented in Table 1 below:

Table 1

​ Homicide
  • Murder
  • Attempted/Conspiracy to Murder
  • Manslaughter
  • Driving Causing Death

Recent Sexual Offences

  • Recent Sexual Assault
  • Recent Non-Assaultive Sexual Offences

Historical Sexual Offences

  • Historical Sexual Assault
  • Historical Non-Assaultive Sexual Offences

Assault (Family)

  • Serious Assault (Family)
  • Common Assault (Family)

Assault (Non-Family)

  • Serious Assault (Non-Family)
  • Common Assault (Non-Family)
  • Assault Police Officer

Threatening Behaviour (Family)

  • Threatening Behaviour (Family)
  • Possess Weapon to Cause Fear (Family)

Threatening Behaviour (Non-Family)

  • Threatening Behaviour (Non-Family)
  • Possess Weapon to Cause Fear (Non-Family)

Deprivation of Liberty

  • Kidnapping/Child Stealing
  • Deprivation of Liberty

Robbery

  • Business
  • Non-Business

Burglary

  • Dwelling
  • Non-Dwelling

Stealing of Motor Vehicle

Stealing

  • Stealing From Motor Vehicle (Contents or Parts)
  • Stealing From Retail Premises (Shoplift)
  • Stealing From Dwelling
  • Stealing From Other Premises or Place
  • Stealing as a Servant
  • Stealing (Not Elsewhere Classified)

Property Damage

  • Criminal Damage
  • Damage

Arson

  • Cause Damage by Fire
  • Cause Bushfire
  • Other Fire Related Offences

Drug offences

  • Drug Dealing
  • Cultivate or Manufacture Drugs
  • Drug Possession
  • Possession of Drug Paraphernalia
  • Other Drug Offences

Receiving and Possession of Stolen Property

  • Possess Stolen Property
  • Receiving Stolen Property

Regulated Weapons Offences

Graffiti

Fraud and Related Offences

  • Forgery
  • Fraud (Credit Card)
  • Fraud (Not Elsewhere Classified)

Breach of Violence Restraint Order

  • Breach of Family Violence Restraint Order
  • Breach of Violence Restraint Order
  • Breach of Police Order

Classifications

Offence classification

The WA Police Force uses the Australian and New Zealand Standard Offence Classification (ANZSOC), 2011 when supplying data to the Australian Bureau of Statistics (ABS). This classification was developed by the ABS on behalf of the police agencies of the States and Territories of Australia and New Zealand. The main objective of this standard is to enable comparable reporting of crime statistics across jurisdictions.

The WA Police Force differs from ANZSOC for the recording of the offence ‘Steal Motor Vehicle’ due to differences between ANZSOC and WA Legislation.

The WA Legislation does not require that a vehicle be eligible for registration for use on public roads. Unregistered off-road dirt/trail bikes and quad bikes would therefore be counted in WA motor vehicle theft statistics and not at a national level.

The offence classification used for the publishing of WA Police Force crime statistics is based on a combination of ANZSOC, WA Legislation, and operational reporting requirements.

Family relationship

For WA Police Force purposes a Family Relationship includes:

  • Partner;
  • Ex-partner;
  • Parents;
  • Guardians of children; and
  • Children who reside or regularly stay with involved parties.

Offence Outcome Status Codes

Offence Outcome Status Codes are applied to each offence as a determination of the end state of a recorded offence within an Incident Report. An offence is excluded from recorded crime statistics if the investigation determines that no criminal offence occurred, or the offence has been substituted with an alternate offence, in which case the alternate offence will be counted.

The table below lists each Offence Outcome Status Code and its inclusion in crime statistic offence counts.

Table 2
Offence Outcome Status Code Recorded Offences (July 2017 onwards) Verified Offences (Prior to July 2017)
Under Investigation Yes Yes
No Criminal Offence No Did not exist
Offence Substituted No (alternative offence counted) Did not exist
Unable to Proceed/Charge Yes Did not exist
Complaint Withdrawn Yes Did not exist
False Report No
Reporting person may be charged with the offence of making a false report and a False Report offence created
No
Reporting person may be charged with the offence of making a false report and a False Report offence created
Insufficient Evidence Yes Yes
Offender Processed Yes Yes
Uncleared Yes Yes
Mistakenly Reported No
Replaced by ‘No Criminal Offence’
No
Civil/Other No
Retired
Yes
Statute Barred No
Renamed ‘Unable to Proceed/Charge’
Yes
Withdrawn No
Renamed ‘Complaint Withdrawn’
Yes

Counting methodology

Criminal offences is the counting unit used for the crime statistics published on the WA Police Force website.

Data is compiled based on the date the offence was reported to police by a member of the public or when it was detected by police and was recorded on police systems.

The report date may be different to the date when the offence occurred. For example Historic Sexual Assault offences.

Offences are captured within Incident Reports. Each offence can have multiple victims and/or multiple offenders. The number of offenders or victims may not have a direct correlation to the number of offences counted.

An incident may have more than one of the same offence or different offences, and as such all offences related to that incident are captured in the same Incident Report.

The exception to this recording practice is facilitation offences, such as damage caused gaining entry to a premises for the purpose of burglary. In those circumstances, the burglary only is reported. If damage occurs during the burglary beyond that necessary to facilitate the primary offence of burglary, a damage offence would be generated and reported.These scenarios are represented in Diagrams 1 and 2.

The WA Police Force follow the National Crime Recording Standard (NCRS) (2008), noting that the standard relates to victim counts compared to the WA Police Force which counts criminal offences. Where the WA Police Force differs from the NCRS consultation has occurred with the ABS. The NCRS is an ABS internal publication which was endorsed by the Police Commissioners of each State and Territory of Australia.

The following diagrams illustrate the offence counting rules for the WA Police Force.

Diagram 1: Facilitation offence
Diagram 1: Facilitation offence
Diagram 2: Damage offence
Diagram 2: Damage offence

Rate per 100,000

The rate of offences per 100,000 people in Western Australia is presented in the ‘Year to Date Annual Crime Statistics’ report available on the WA Police Force website. This report provides the rate of offences per 100,000 people for Western Australia, the Metropolitan Region, the Regional WA Region and the 11 police districts.

The use of a rate per 100,000 people is an internationally/nationally recognised standard for measuring the prevalence of crime over time and between different geographical areas as it adjusts the number of offences in accordance with variations in population.

Rates are calculated using the Estimated Resident Population (ERP) published by the Australian Bureau of Statistics (ABS).

The offence rate per 100,000 people is calculated using the following formula:

  • Offence rate per 100,000 = (Offence count ÷ ERP) × 100,000

The ERP used corresponds to the geographical area of the offence count.

Sanction rate

The sanction rate is an indicator of the effectiveness of the WA Police Force in achieving selected offence investigation outcomes such as the processing of an offender.

From July 2017 onwards the sanction rate is calculated using the following formula:

  • Sanction rate = (Number of offences with a sanction outcome ÷ Number of recorded offences for the same time period) × 100.

Prior to July 2017 the sanction rate is calculated using the following formula:

  • Sanction rate = (Number of offences with a sanction outcome ÷ Number of verified offences for the same time period) × 100.

The sanction rate may exceed 100% if the number of offences with a sanction outcome recorded in a time period is greater than the number of new offences recorded in the same time period.

The sanction rate for offences is presented in the ‘Year to Date Annual Crime Statistics’ report available on the WA Police Force website. This report provides the sanction rate for Western Australia, the Metropolitan Region, the Regional WA Region and the 11 police districts.

Data comparability

Between May and July 2017, changes to recording and reporting practices were implemented across the WA Police Force. Hence, comparability of data published prior to this date should be undertaken with caution.

Changes that have been implemented are:

  • Adoption of the Australian and New Zealand Standard Offence Classification (2011);
  • Changes to Offence Outcome Status Codes;
  • Changes to recording practices;
  • Additional offence types available for selection in the recording of incidents;
  • Counting rules aligned with the National Crime Recording Standard; and
  • Administrative system (Incident Management System (IMS)) updated to support changes in recording practices.

Australian and New Zealand Standard Offence Classification (2011)

The WA Police Force has moved to the contemporary national standard for offence classification, Australian and New Zealand Standard Offence Classification (ANZSOC), 2011, from the former Australian Standard Offence Classification (ASOC), 1997.

Changes between ASOC (1997) and ANZSOC (2011) are documented in the explanatory notes of the ANZSOC (2011) publication on the ABS website.

Changes to Offence Outcome Status Codes

From July 2017, the Offence Outcome Status Codes which are applied to offences within Incident Reports have been contemporised. This has involved retainment of some of the existing status codes, amendment of some existing status codes, new status codes and retirement of obsolete status codes. The updated list of available status codes provides a greater ability for comparison across other law enforcement jurisdictions (See Table 2).

Changes to recording practices

The WA Police Force has developed a training course for police officers and police staff which explain the changes in recording practices that are required to ensure alignment with national standards.

This promotes coherence and consistency in recording practices and improves the reliability of the data for statistical purposes.

Additional offence types

During June and July 2017, new offence types were added to the administrative system that the WA Police Force uses to record incidents. These were added to meet both changes to legislation and provide better clarity in reporting.

The new offence types listed below only apply to data from June 2017 onwards:

  • Stealing From Motor Vehicle (Contents or Parts);
  • Stealing From Retail Premises (Shoplift);
  • Stealing From Dwelling;
  • Stealing From Other Premises; and
  • Fraud (Credit Card).

The offence type of ‘Fraud (Not Elsewhere Classified)’ has a series break at June 2017. Prior to this date this offence type included credit card fraud.

The offence type ‘Breach of Family Violence Restraint Order’ includes the offences of 'Breach of Family Violence Restraint Order' introduced in July 2017 due to legislation changes and 'Breach of Violence Restraint Order' where a family relationship is determined to exist.

Counting rules

From July 2017, the counting rules applied by the WA Police Force to offence counts are aligned where practicable with the National Crime Recording Standard.

Changes to recording practices which impact on the reporting of offence counts include:

  • Not recording facilitation offences (e.g. damage on a burglary);
  • Not recording the same offence multiple times within an Incident Report for a single victim, (The exception being sexual offences where multiple offences may be recorded against the same victim);
  • Instruction on the definition of what constitutes a 'motor vehicle' so that the correct offence can be applied; and
  • Clearer definitions and instructions for the application of offences and Offence Outcome Status Codes.

Administrative system changes

The administrative system used by the WA Police Force, Incident Management System (IMS), has been modified so police officers can comply with the recording and reporting practices introduced between May and July 2017.

This includes:

  • Implementation of ANZSOC 2011;
  • Additional offence types;
  • New Offence Outcome Status Codes; and
  • Business rules that support recording of offences in line with the NCRS in regards to facilitation offences.

Related publications

The WA Police Force contributes to the ABS suite of crime statistics which encompasses data from each of the States and Territories of Australia.

The ABS publications that the WA Police Force contributes to are:

Recorded Crime - Victims, Australia - 4510.0

Recorded Crime - Offenders - 4519.0

Care should be taken when comparing the crime statistics (offence counts) on the WA Police Force website with ABS data due to differing methodologies and counting rules used for Victim, Offender and Offence counts.