Criminal justice statistics user guide
This document provides detailed information on the Criminal Proceedings and Reconviction Rates in Scotland statistical bulletins. It is designed as a reference guide with explanatory notes regarding issues and classifications which are crucial to the production and presentation of criminal justice statistics in Scotland.
3. Data quality, processing and confidentiality
3.1 Data quality
The Criminal History System (CHS) was not designed purely for statistical purposes. However, actions and processes have been put in place to ensure that Scottish Government statisticians understand the data. The data requirements for these extracts are contained in a joint specification document that has been agreed between Police Scotland and the Scottish Government.
Monthly extracts are uploaded onto a Scottish Government database at which point validation checks are undertaken to ensure a realistic number of records are added to the database. Checks are also made to ensure values for charges, court locations and disposal type are recognised. If any unexplained patterns or unrecognised codes are identified at the data upload stage, further investigations are undertaken. It may be necessary, at times, to go back to Police Scotland to verify the data.
Charge codes are the operational codes used to identify the crime or offence and are linked to legislation. New charge codes for crimes and offences under emerging legislation are created by the Crown Office and Procurator Fiscal Service (COPFS) on a monthly basis and shared with the Scottish Government. When new codes are identified at the data upload stage, they are verified and then added to a look-up table of recognised codes.
The Scottish Government is responsible for mapping each charge code to a crime code, which forms the basis of the crime code classification. There are around 600 crime codes used in the current statistical crime classification. These are aggregated into the 50 crime categories reported in the bulletin. This mapping is agreed with individuals from Police Scotland and COPFS and enables consistent and comparable reporting between justice organisations.
When we receive data from the CHS as described above, the monthly extracts are processed into our local database. In preparation for the annual Criminal Proceedings publication, a process is run which collates the year’s data into a format that allows us to validate and analyse the information.
3.2 Data Validation: Criminal History System
Numerous data cleaning checks are performed and where issues have occurred these have been reported in the relevant bulletin. These are then incorporated into future validation rules.
Once this dataset is created, validation procedures are carried out as follows.
Automated validation procedures and manual checks to identify any unrealistic data values e.g. long custodial sentences for petty crimes or short sentences for the most serious of crimes. Effort is also made to clean up records for which key information is missing e.g. missing court locations or age/sex of the offender. These are referred back to Police Scotland, Scottish Court and Tribunal Service (SCTS) or COPFS for correction or for explanation of any unusual circumstances.
Other checks are carried out as necessary for any changes to the justice system. For example, when new legislation is implemented, checks are undertaken to ensure cases are coming through the system at a realistic rate.
Trends in the statistics are compared against case processing information published by COPFS and management information provided by SCTS to ensure that the volume of court proceedings is consistent. Information is compared by court type (e.g. high court, sheriff court etc.) to identify any differences.
Further checks are undertaken by crime type, sentence type and other characteristics to identify any errors and unusual values. As an extra level of assurance, policy experts within the Scottish Government are consulted to identify why any significant changes may have occurred. Any relevant contextual information is then added to the criminal proceedings bulletin.
Similar consultation is undertaken with COPFS, SCTS and Police Scotland wherein results are shared purely for quality assurance purposes. Insight at an operational level provides invaluable feedback and informs whether further investigation of statistical quality is required.
In recent years, we have carried out much more extensive quality assurance with external agencies. The purpose of this is to ensure the accuracy and quality of the statistics published. COPFS have identified that there may be a small number of court proceedings (often involving multiple charges and of a complex nature) which are being recorded as separate court cases which, in fact, should only be reported as one. The effect of this would be to over-estimate the true number of court proceedings. Investigations suggest that this affects all crime types, though to varying degrees.
3.3 Data validation: Reconvictions
In preparation for the Reconviction Rates bulletin, the data undergoes processing to calculate the frequency and prevalence of reconvictions. The numbers are manually checked to determine whether there are any unusual values. If so, then the calculations are rechecked. Like the Criminal Proceedings in Scotland publication, the figures in the reconvictions bulletin have undergone a further round of checks by Scottish Government statisticians, and policy experts within the Scottish Government are again consulted to provide insight and context to any significant changes in the figures.
Further quality assurance and checking on both the Criminal Proceedings and Reconviction Rates bulletins is undertaken on the statistics by members of Scottish Government Justice Analysis and Strategy team.
3.4 Data Confidentiality
The Scottish Government are legally able to collect the data for these publications as Section 84(1 & 2) of the Police and Fire Reform (Scotland) Act 2012 states that the “Scottish Police Authority must provide Scottish Ministers with reports, statistics or other information relating to the Police Service or functions, and the state of crime”.
Court proceedings are held in public and may be reported on by the media unless the court orders otherwise, for example where children are involved.
While our aim is for the statistics in our bulletins to be sufficiently detailed to allow a high level of practical utility, care has been taken to ensure that it is not possible to identify an individual or organisation and obtain any private information relating to them.
We have carried out a data protection impact assessment on our handling and use of personal data which is available along with a privacy notice.
We have assessed the risk of individuals being identified in the published tables and have established that no private information can be identified. Where demographic information is provided, this is done either in wider categories of ages (for example tables 6, 21 and 22) or in numbers per 1,000 population (Table 5). This ensures that where there are small numbers, personal information about individuals cannot be identified.
To maintain the security and confidentiality of the data received from the data suppliers, only a small number of Scottish Government statisticians and statistical support officers have access to the datasets in the various stages of processing outlined above. The only personal details received by the Scottish Government in the data extract are those which are essential for the analyses in our statistics and do not include the names of offenders.
3.5 Revisions
The CHS is not designed for statistical purposes and is dependent on receiving timely information from Justice partner organisations. A pending case on the CHS should be updated in a timely manner but there are occasions when slight delays happen. Recording delays of this sort generally affect High Court disposals more than those of other types of court, as they are the most complex and lengthy trials. Also, the court may await reports before passing a sentence, so there may be a gap between when the defendant is found guilty and when a sentence is given. We only receive the data when the sentence details are given.
The figures given in the criminal proceedings bulletin reflect the details of court proceedings as recorded on the CHS, that were concluded on or by 31 March of the relevant financial year. The figures are provided to the Scottish Government up to the end of March of the following year. Any subsequent updates on court disposals made will be incorporated into future bulletins and therefore some figures for previous years (in particular those relating to the High Court) are likely to be subject to minor revisions.
These recording delays mean that figures for the most recent financial year should be considered provisional as future bulletins may provide updates.
Records may be changed on the CHS, and these updates are included in the monthly data extracts that are sent to us. In some cases the sentence date may be changed due to changes in the sentence. This may move some of the sentences into the following financial year.
When revisions are required, they comply with the Scottish Government's policy on revisions and corrections.