Definitions and measurements
Source: data.gov.uk (2018-05-25)

Proven Re-offending statistics. Key statistics on proven reoffending in England and Wales. It gives proven reoffending figures for offenders who were released from custody, received a non-custodial conviction at court, or received a caution or reprimand.

Proven re-offending statistics: 
definitions and measurement 
 
Published October 2012 

 
Contents 
Proven re-offending statistics quarterly bulletin 
3 
Early estimates of proven re-offending statistics 
11 
Local adult re-offending statistics quarterly bulletin 
14 
Data quality 
16 
Statistical modelling and coefficients 
26 
Appendix A: List of serious offences 
34 
Appendix B: Glossary of terms 
39 
Appendix C: Comparison of the three measures of re-offending 
47 
Contact details and further information 
48 
 
 2

 
Proven re-offending statistics quarterly bulletin 
Background 
The Ministry of Justice launched a statistical consultation on improvements 
to the transparency and accessibility of our information in 2010 and a 
response to the consultation was published in March 2011. One aspect of 
the consultation was the measurement of proven re-offending. Responses 
have supported the proposals to move to a single framework for measuring 
re-offending where adult and youth data can be provided at the national and 
local level on a consistent basis. The response to the consultation is 
available here: 
 
www.justice.gov.uk/downloads/consultations/improvements-moj-statistics-
consultation-response.pdf 
 
Prior to this consultation there were six different measures of proven re-
offending: 
 
 national adult proven re-offending; 
 
 local adult proven re-offending; 
 
 national youth proven re-offending; 
 
 local youth proven re-offending; 
 
 prolific and other priority offending (PPO); and 
 
 drug-misusing proven offending. 
 
The current framework for measuring proven re-offending integrates these 
approaches into a single framework. This allows users to: 
 
 form a clear picture of proven re-offending at national and local 
levels; 
 
 compare adult and youth results, and enable other work on transition 
between the youth and adult system; 
 
 understand how results for different offender groups (such as those 
managed by the prison and probation services, those under the PPO 
schemes, drug-misusing offenders, first time entrants, etc.) fit into the 
overall picture on proven re-offending; and 
 
 continue to analyse proven re-offending behaviour for particular types 
of offender. 
 3

 
Measurement 
 
The underlying principle of measuring re-offending (or recidivism, which is 
the most commonly used term internationally) is that someone who has 
received some form of criminal justice sanction (such as a conviction or a 
caution) goes on to commit another offence within a set time period. 
 
Measuring true re-offending is difficult. Official records are taken from either 
the police or courts, but they will underestimate the true level of re-offending 
because only a proportion of crime is detected and sanctioned and not all 
crimes and sanctions are recorded on one central system. Other methods of 
measuring re-offending, such as self report studies, are likely to also 
underestimate the rate. 
 
Following the Ministry of Justice consultation on Improvements to Ministry of 
Justice Statistics (2010), a proven re-offence is defined as any offence 
committed in a one year follow-up period and receiving a court conviction, 
caution, reprimand or warning in the one year follow-up or a further six 
month waiting period. The data source is the extract of the Police National 
Computer (PNC) held by the Ministry of Justice. 
 
Definitions for the measurement of proven re-offending 
 
Cohort 
This is the group of individuals whose re-offending is measured. For the 
Proven Re-offending Statistics Quarterly Bulletin, this is defined as all 
offenders in any one year who received a caution (for adults), a final 
warning or reprimand (for juveniles), a non-custodial conviction, or were 
discharged from custody. 
 
Offenders who were discharged from custody or secure accommodation 
(juveniles only) or commenced a Court Order are matched to the PNC 
database. A proportion of cases are lost in this process because they 
cannot be matched (see the section below titled “Matching offender records” 
for further details). Additionally, offenders who appear multiple times in the 
cohort are only included once (see the section below titled “Multiple offender 
entries” for further details). 
 
The group of offenders whose offending behaviour is proven is likely to be a 
sub-group of all active offenders. The Offending, Crime and Justice Survey 
(2003)1 estimated that around one in ten people in England and Wales aged 
between ten and 65 had committed an offence in the previous 12 months, 
                                            
 4
1 The Offending, Crime and Justice Survey (2003) was a random probability survey of 
10,079 people aged from ten to 65 and asked people about their offending history. Like any 
such survey, its accuracy is dependent upon the level of honesty with which respondents 
completed the survey. 

 
which translates into approximately 3.8 million people. This compares to 
632,000 offenders in the 2002 cohort used to measure proven re-offending, 
underlining that the offenders whose proven re-offending behaviour is 
presented in the Proven Re-offending Statistics Quarterly Bulletin are a 
small and probably unrepresentative sample of the population of all active 
offenders. 
 
Index disposal (sentence type) 
The index disposal of the offender is the type of sentence the offender 
received for their index offence. For the Proven Re-offending Statistics 
Quarterly Bulletin, this is defined as custody, court order, other disposal 
resulting from a conviction at court, such as a fine or discharge, caution 
(adult offenders), reprimand or final warning (young offenders). 
 
Index offence 
The index offence is the proven offence that leads to an offender being 
included in the cohort. An offence is only counted as an index offence if it is: 
 
 recordable (see below); 
 
 committed in England and Wales; 
 
 prosecuted by the police; and 
 
 not a breach offence. 
 
There are around 3,000 offence codes on the PNC and these have been 
classified into the following 21 groups: 
 
 violence (non serious) 
 
 violence (serious) 
 
 robbery 
 
 public order or riot 
 
 sexual 
 
 sexual (child) 
 
 soliciting or prostitution 
 
 domestic burglary 
 
 other burglary 
 
 theft 
 
 handling 
 
 5

 
 fraud and forgery 
 
 absconding or bail offences 
 
 taking and driving away and related offences 
 
 theft from vehicles 
 
 other motoring offences 
 
 drink driving offences 
 
 criminal or malicious damage 
 
 drugs import/export/production/supply 
 
 drugs possession/small scale supply 
 
 other 
 
Start point (index date) 
This is the set point in time from when proven re-offences are measured. 
For the Proven Re-offending Statistics Quarterly Bulletin, this is defined as 
the date of prison discharge, date of court conviction for non-custodial 
sentences, date of receipt for a caution, reprimand or final warning or the 
date of a positive drug test. 
 
Follow-up period 
This is the length of time proven re-offending is measured over. For the 
Proven Re-offending Statistics Quarterly Bulletin, this is defined as 12 
months from the start point. 
 
Waiting period 
This is the additional time beyond the follow-up period to allow for offences 
which are committed towards the end of the follow-up period to be proven 
by a court, resulting in a conviction, caution, reprimand or final warning. For 
the Proven Re-offending Statistics Quarterly Bulletin, this is six months. 
 
Figure 1 below illustrates why different offences for an example offender are 
included or excluded in the proven re-offending measure. 
 
 6

 
Figure 1: How events of re-offending are included in the measure? 
 
 
 
Events A to E all occur in the one year follow-up period, but events F and G 
are outside this period, so would not be counted. Events A to D are all 
counted because they were all proven within the one year follow-up period 
or the further six month waiting period, but event E, even though the offence 
took place in the one year follow-up period, would not be counted, as the 
conviction did not occur within either the one year follow-up period, or the 
further six month waiting period. The offender has, therefore, committed 
seven proven offences during the one year follow-up period (two for event 
A, one for event B, three for event C, and one for event D). 
 
Proven re-offence 
Offences are counted as proven re-offences if they meet all of the following 
criteria: 
 
 They are recordable. Not all offences are on the PNC and more 
recordable offences are entered than non-recordable offences. 
Analysis comparing offences proven at court with offences recorded 
on the PNC suggests the most cost common offences that are not 
recorded relates to motor vehicles, e.g. using a motor vehicle whilst 
uninsured against third party risks, speeding offences, keeping a 
vehicle on the highway without a driving licence or television licence 
evasion. 
 
 They were committed in England or Wales. 
 
 They are offences that were prosecuted by the police. PNC data is 
collected and input by the police and offences prosecuted by the 
police are likely to be recorded more comprehensively on the PNC 
than offences that are prosecuted by other organisations. For 
example, benefit fraud is prosecuted by the Department for Work and 
Pensions. Therefore, benefit fraud offences may be poorly 
represented on the PNC. 
 
 Offences are only counted if they are proven through caution (for 
adults), reprimands or final warnings (for juveniles) and court 
convictions. Offences that are not proven, or which meet with other 
responses from the Criminal Justice System, are not counted. The 
Offending, Crime and Justice Survey (2003) estimated that six per 
 7

 
cent of all offences resulted in any contact with the Criminal Justice 
System. 
 
 The offence is not a breach offence, i.e. breach of a court order, 
since we are only interested in new offences. 
 
Adjusted baseline (predicted rate) 
Proven re-offending is related to the characteristics of offenders which 
means that any overall rate of proven re-offending will depend, in part, on 
the characteristics of offenders coming into the system (just as the 
examination pass rate of a school will be related to the characteristics of its 
pupils). We use a modelling technique to produce a baseline figure adjusted 
to match the characteristics of the cohort we are comparing. For more 
details on this, refer to the chapter on “Statistical modelling and 
coefficients”. 
 
Measures of proven re-offending 
Proven re-offending data are presented in the following ways: 
 
 The number of offenders. 
 
 The proportion of offenders who are proven re-offenders. 
 
 The average number of proven re-offences among re-offenders. 
 
 The average number of proven re-offences among all offenders 
including those who committed no proven re-offences (previously the 
frequency rate). 
 
 The proportion of proven offenders who committed a proven serious 
re-offence against the person. Refer to Annex A for details on what 
counts as a serious offence. 
 
 The proportion of proven offenders who committed a proven serious 
acquisitive re-offence. Refer to Annex A for details on what counts as 
a serious acquisitive offence. 
 
 The proportion of offenders who are proven to re-offend, adjusted to 
control for changes in offender characteristics. This measure is 
different from the other measures in that it does not come from actual 
re-offences, but from a statistical model created for the baseline year 
of 2008. This gives a better indication of actual change against a 
baseline. Refer to the chapter on “Statistical modelling and 
coefficients” for further details. 
 
Multiple offender entries 
Each offender is tracked over a fixed period of time and any proven offence 
committed in this period is counted as a proven re-offence. A multiple 
offender entry refers to an offender who, after entering the cohort in a given 
year, commits a re-offence and is either cautioned, discharged from prison 
 8

 
or gets a non-custodial conviction in the same cohort year. This re-offence 
could also be included as a second entry for this offender into the cohort. 
 
Figure 2: Example of an offender with multiple offender entries 
 
 O
 
 
 
ffender 
Cautioned
Re-offence 1 
Offender starts a 
community 
sentence 
Re-offence 2 
Offender 
sentenced to 
3mnths in prison 
then released 
Re-offence 3 
1 year cohort period
Offender 
Cautioned
Offender 
Cautioned
Re-offence 1 
Offender starts a 
community 
sentence 
Re-offence 2 
Offender 
sentenced to 
3mnths in prison 
then released 
Offender 
sentenced to 
3mnths in prison 
then released 
Re-offence 3 
1 year cohort period
 
To date, publications have avoided the double counting of these multiple 
offender entries (MOE) by only counting an individual once based on their 
first proven offence in the relevant time period. In the illustration above, the 
caution would be counted as the index disposal and the further two proven 
offences would be counted as re-offences. This avoids double counting of 
proven re-offences. 
 
In this publication the main tables (tables 1 to 17) in the report have been 
produced on the basis of the 'first proven offence in the relevant time period’ 
which led to an offender being included. This provides a picture of proven 
re-offending which is consistent with previous publications and tracks an 
offender, irrespective of the disposal they receive, to when they commit a 
proven re-offence. 
 
The measure of proven re-offending now covers all offenders in any one 
year instead of the first quarter of a calendar year as in previous proven re-
offending publications. The result is many more offenders with multiple 
entries. 
 
In addition, including cautions to identify a proven offence means many 
offenders’ first offence will be associated with a caution since cautions 
account for around a third of adult offenders in one year. Table 1 shows the 
number of offenders in each cohort period by their number of entries. 
 
Table 1: Number of offenders and their respective number of entries for 
2000, 2002 to 2010 cohorts 
 
Multiple
2008 
2009 
Offender Entries
2000
2002
2003
2004
2005
2006
2007
2010
1
512,551
522,376
544,032
551,265
582,840
622,096
638,495
610,329
578,644
535,394
2x 
75,311
77,813
81,651
78,969
81,120
87,589
91,695
88,207
83,785
79,067
3x 
4x 
19,565
21,208
22,073
20,855
20,926
21,974
23,757
23,662
22,125
21,466
6,195
6,689
7,074
6,835
6,725
6,807
7,652
7,917
7,360
7,425
5x 
6 to 10x 
1,998
2,314
2,392
2,357
2,355
2,425
2,795
2,911
2,938
2,909
1,240
1,510
1,689
1,641
1,505
1,513
1,966
2,341
2,308
2,368
Greater than 10x 
164
155
129
131
119
115
114
160
202
193
Total MOEs
104,473
109,689
115,008
110,788
112,750
120,423
127,979
125,198
118,718
113,428
% of total cohor  
t
Cohort 
16.9%
17.4%
17.5%
16.7%
16.2%
16.2%
16.7%
17.0%
17.0%
17.5%
617,024
632,065
659,040
662,053
695,590
742,519
766,474
735,527
697,362
648,822
 
The number of offenders with multiple entries has remained fairly constant 
over time - the proportion of the total that had multiple offender entries has 
remained at about 16 to 17 per cent between 2000 and 2010. 
 9

 
Proven re-offending by index disposal, probation trust and prison 
In order to measure proven re-offending on a consistent and representative 
basis by offender management groups, it is necessary to distinguish 
between the disposal (sentence) types that led to an offender being 
included. Doing this allows the cohort to be defined according to the relative 
start point of an offender’s interaction with the prison (released from 
custody) or probation services (court order commencement). 
 
Tables 18 to 21 provide re-offending rates by disposal (sentence) types, 
These are produced on the basis of an individual’s first disposal (sentence) 
in that category. In the illustration above the individual would appear once in 
the caution category, once in the community order category and once in the 
custody category. These tables will include an overall prison and probation 
proven re-offending rate which will be the figures we quote publicly. 
However, these figures should not be used when comparing proven re-
offending rates across different disposals to compare effectiveness. Instead 
the ‘Compendium of Re-offending Statistics and Analysis 2011’ (at the link 
below) should be referred to as this analysis controls for offender 
characteristics in order to give a more reliable estimate of the relative 
effectiveness of different disposals. 
 
www.justice.gov.uk/statistics/reoffending/compendium-of-reoffending-
statistics-and-analysis 
 
Tables 22 to 25 provide re-offending rates by individual prison and probation 
trust. These are produced on the basis of an individual’s first disposal from 
each specified prison or probation trust. If the individual offender is 
discharged from two different prisons in the year they will appear in both of 
the prison’s re-offending rates. The same applies for offenders commencing 
court orders in more than one probation trust within the year. This is to allow 
prisons and probation services to track their caseload of offenders. 
 
10

 
Early estimates of proven re-offending statistics 
Background 
Responses from the consultation and from earlier engagement with 
representatives of front-line offender management services supported the 
proposal to produce early estimates of proven re-offending using shorter 
follow-up and waiting periods. This is intended to provide offender 
managers feedback on the proven re-offending trends of offenders they are 
working with in time for them to adjust or build on offender management 
operational policy. This section of the new bulletin addresses these issues. 
 
Early estimates of proven re-offending are presented for four particular 
offender groups who are subject to specific offender management 
arrangements. These are offenders managed by the probation service, 
Prolific and other Priority Offenders (PPO) who are managed by a 
partnership of local front-line services, drug-misusing offenders who are 
managed by Drug Action Teams, and young offenders who are managed by 
Youth Offending Teams. 
 
Proven re-offending for the early estimates is measured in exactly the same 
way as for the headline proven re-offending measure except that the follow-
up period and waiting period are both three months each. (For the headline 
measure of proven re-offending they are 12 months and six months, 
respectively.) 
 
The headline figures and early estimates differ in the following ways: 
 
 Early estimates of proven re-offending rates are considerably lower 
than in the headline publication. This is because they cover a shorter 
time period. 
 The shorter follow-up period and waiting period allow rates to be 
calculated for more recent groups of proven offenders. 
 Early estimates of proven re-offending rates provide local offender 
management services with information on proven re-offending trends 
for the offenders they are working with. The headline re-offending 
publication presents the public with information on a wide range of 
proven re-offending trends and provides proven re-offending rates by 
a variety of breakdowns, such as age, gender, disposal, etc. 
 The shorter follow-up period and waiting period provides insufficient 
time for many serious re-offences to be committed and convicted. For 
this reason, early estimates of proven re-offending rates do not 
include information on serious re-offending. 
 Results in the headline measure are compared to a baseline rate, 
adjusted for changes in the offender profile. This relies on an 
 
11

 
estimate of the relationship between offender characteristics and 
proven re-offending behaviour over 12 months. An equivalent 
estimate has been carried out for the proven re-offending behaviour 
of offenders commencing court order over three months. This uses 
the same variables as the headline measure plus additional variables 
to ensure that the actual and predicted rates are identical for every 
probation trust in the baseline period (2008). The tables 
accompanying the early estimates present the adjusted baseline for 
each trust, and the text identifies those trusts where the actual rate is 
significantly higher or lower than the predicted rate in the most recent 
results available. 
Measurement 
Coverage 
Results are provided for four types of offenders: probation offenders by 
probation trust, PPO offenders by upper-tier local authority, drug-misusing 
offenders by Drug Action Team, and young offenders by Youth Offending 
Team. 
 
Cohort 
For probation offenders, the cohort is made up of all offenders who 
commenced a court order within a 12 month period. For PPO offenders, the 
cohort is made up of all offenders identified as a PPO who were discharged 
from custody, convicted at court, received a caution (adults), reprimand or 
final warning (juveniles) or tested positive for opiates or cocaine within a 12 
month period. For drug-misusing offenders, the cohort is made up of all 
offenders identified as drug-misusing who were discharged from custody, 
convicted at court, received a caution or tested positive for opiates or 
cocaine within a 12 month period. For juveniles, the cohort is made up of all 
young offenders who were discharged from custody, convicted at court or 
received a reprimand or final warning within a 12 month period. 
 
Start point (index date) 
Same as for the headline proven re-offending figures presented in the Re-
offending Statistics Quarterly Bulletin. 
 
Follow-up period 
This is the length of time proven re-offending is measured over. For the 
Early Estimates of Proven Re-offending, this is defined as three months 
from the start point. 
 
Waiting period 
This is the additional time beyond the follow-up period to allow for offences 
which are committed towards the end of the follow-up period to be proven 
by a court, resulting in a conviction, caution, reprimand or final warning. For 
the Early Estimates of Proven Re-offending Statistics, this is three months. 
 
Proven re-offence 
Same as for the headline proven re-offending figures presented in the Re-
offending Statistics Quarterly Bulletin. 
 
12

 
 
Adjusted baseline (predicted rate) 
Proven re-offending is related to the characteristics of offenders which 
means that any overall rate of proven re-offending will depend, in part, on 
the characteristics of offenders coming into the system (just as the 
examination pass rate of a school will be related to the characteristics of its 
pupils). We use a modelling technique to produce a baseline figure adjusted 
to match the characteristics of the cohort we are comparing. For more 
details on this, refer to the chapter on “Statistical modelling and 
coefficients”. 
 
Multiple offender entries 
Same as for the headline proven re-offending figures presented in the Re-
offending Statistics Quarterly Bulletin. 
 
13

 
Local adult re-offending statistics quarterly 
bulletin 
Background 
Proven re-offending results from this measure have been published by the 
Ministry of Justice since February 2009 at Government Office Region, 
probation trust and local authority level. This data is used to measure 
probation performance and the Ministry of Justice will continue to produce 
these measures while offender management systems still require them. The 
Local Adult Re-offending Statistics Quarterly Bulletin can be found on the 
Ministry of Justice website at the following link: 
 
www.justice.gov.uk/statistics/reoffending/local-adult-reoffending 
 
The local proven re-offending data measure the re-offending of all offenders 
on the probation caseload. This includes offenders on licence and serving 
court orders. 
 
Local proven re-offending rates use the same follow-up period and waiting 
period to those for the early estimates. However, there are several key 
differences between the local measure and the early estimates. These 
include: 
 
 The sample of offenders - local rates are estimated using all 
offenders on the probation caseload, including those on licence and 
those serving court orders. Offenders on the caseload are identified 
through four ‘snapshots’ of the caseload, which are taken each 
quarter. Offenders are included if they are on the caseload even if 
they have been on licence or serving the court order for longer than 
12 months. The early estimates are based on offenders who 
commence a court order within a 12 month period. 
 Local rates define the period reported on by the period of re-
offending. The early estimates refer to the year of the index disposal. 
Measurement 
 
Cohort 
All offenders on the probation caseload taken from four quarterly snapshots. 
 
Start point 
The date of the snapshot. 
 
Follow-up period 
This is the length of time proven re-offending is measured over. For the 
Local Adult Re-offending Statistics Quarterly Bulletin, this is defined as three 
months from the start point. 
 
 
14

 
Waiting period 
This is the additional time beyond the follow-up period to allow for offences 
which are committed towards the end of the follow-up period to be proven 
by a court, resulting in a conviction, caution, reprimand or final warning. For 
the Local Adult Re-offending Statistics Quarterly Bulletin, this is three 
months. 
 
Proven re-offence 
Same as for the headline proven re-offending figures presented in the Re-
offending Statistics Quarterly Bulletin. 
 
Adjusted baseline (predicted rate) 
The predicted rate is the proportion of offenders we would expect to re-
offend given the known characteristics of the offenders in the snapshot and 
re-offending rates in the baseline period. More detail on the predicted rate, 
and the statistical model used to calculate it, is provided in Appendix B of 
the Local Adult Re-offending Statistics Bulletin. 
 
15

 
Data quality 
 
The data required for measuring proven re-offending are based on a range 
of data sources (prison data, probation data, identification of drug-misusing 
offenders, identification of prolific and other priority offenders, young 
offenders in secure accommodation, and criminal records from the Police 
National Computer) from a range of agencies (the National Offender 
Management Service, probation trusts, the Youth Justice Board, Drug 
Action Teams, local authorities and the National Police Improvement 
Agency). These figures have been derived from administrative IT systems 
which, as with any large scale recording system, are subject to possible 
errors with data entry and processing. 
 
Police National Computer data  
 
Information regarding the proven re-offending behaviour of offenders has 
been compiled using the Ministry of Justice’s extract from the Police 
National Computer (PNC). The process involves matching offender details 
from the prison and probation data to the personal details recorded on the 
PNC. A proportion of cases cannot be matched and the figures presented in 
Table 2 below are expressed as a percentage of the offenders that are 
matched. Like any large scale recording system, the PNC is subject to 
errors with data entry and recording. The PNC is regularly updated so that 
further analysis at a later date will generate revised figures. 
 
The quality of the information recorded on the PNC is generally assumed to 
be relatively high as it is an operational system on which the police depend, 
but analysis can reveal errors that are typical when handling administrative 
datasets of this scale. The extent of error or omitted records on the PNC is 
difficult to estimate because it is a unique data-source. As a result, there is 
not always an obvious source of data to provide a baseline from which to 
assess data quality. For some types of results, however, comparisons can 
be made. For example, the trend in receptions into prison in each month is 
very similar using the PNC and prisons data (see below for details). 
Although the number of receptions recorded on the PNC is consistently 
slightly lower because prisons data include cases on remand whereas the 
PNC does not. Another example is the number of cases that are given a 
custodial sentence, broken down by offence type, which is similar using the 
PNC and the Court Proceedings Database with a match rate of 97 per cent. 
 
 A number of improvements are routinely carried out: 
 
 Updates to the coding and classification of offences and court 
disposals, including the reduction of uncoded offences, the reduction 
in the use of miscellaneous offence codes and the clarification of the 
coding of breach offences; 
 Updates to the methods used to identify the primary offence, where 
several offences are dealt with on the same occasion, and the 
 
16

 
methods used to identify the primary disposal, where an offence 
attracts more than one court disposal; and 
 Removal of some duplication of records within the database resulting 
in improvements to the efficiency and reliability of the matching 
process. 
Prison data 
 
Prison establishments record details for individual inmates on the prison IT 
system (Prison-NOMIS or LIDS). The information recorded includes details 
such as date of birth, gender, religion, nationality, ethnic origin, custody 
type, offence, reception and discharge dates and, for sentenced prisoners, 
sentence length. The data from individual prison establishments then feeds 
through to a central computer database, called the Inmate Information 
System (IIS). 
 
In May 2009, the National Offender Management Service (NOMS) began 
the roll-out of a new case management system for prisons (Prison-NOMIS). 
During the phased roll-out, data collection issues emerged that affected the 
supply of data for statistical purposes from July 2009 to February 2010. 
Specifically, statistical information on sentence length and offence group are 
not available on any of our prison datasets for this period. 
 
In order to ensure the fullest possible set of data from July 2009 to February 
2010, sentence lengths were estimated for those prisoners received or 
discharged before the problems were resolved. At the point when the 
problems were resolved, a small number of prison establishments were still 
using the old LIDS case management system; data for prisoners received or 
discharged from these prisons was assumed to be unaffected. 
 
For those prisoners received or discharged from prisons operating Prison-
NOMIS, efforts were made to populate their record with the correct 
sentence length using other data extracts. For example, many prisoners 
discharged in January 2010 were originally received into prison prior to July 
2009, so their sentence length was taken from unaffected datasets before 
the problems began. Similarly, the majority of those received in early 2010 
were still in prison in March 2010 when the problems were resolved, so the 
sentence length from the corrected prison population data was used. 
 
Where it was not possible to populate a sentence length using other 
datasets, prisoners were allocated a sentence length band based on the 
number of days they spent in custody (taking account of early release 
schemes where relevant). 
 
As a check on the methodology, an alternative estimation process was 
designed and the number of discharges in each sentence length band for 
the second half of 2009 was compared using the two methods. 
 
A number of estimation methods were considered and tested on the 2008 
data (prior to the data problems) to see which yielded estimates closest to 
the actual 2008 data. This identified the following method: 
 
17

 
 
1. Calculate data for the first half of the year as a proportion of the full 
calendar year, for each year from 2001 to 2008; separately for each 
sentence length band or offence group (the two key breakdowns to 
be estimated). 
 
2. Apply the average of these proportions to the January to June 2009 
data to estimate the 2009 annual totals; separately for each sentence 
length band or offence group. 
 
3. Scale the estimated numbers in each sentence length band or 
offence group to sum to the annual total recorded in the raw data 
(where the totals are known to be correct). 
 
The maximum difference between the two approaches was 2.6 per cent in 
the band ‘12 months to less than 4 years’; for all other bands the difference 
was less than 1 per cent. 
 
Indeterminate sentence prisoners 
In addition to the above, data on the discharge of prisoners on 
indeterminate sentence (prisoners given a life sentence or an Indeterminate 
sentence for Public Protection (IPP) is provided from the Public Protection 
Unit Database (PPUD). This holds data jointly owned by the Offender 
Management and Public Protection Group (OMPPG) in NOMS and the 
Parole Board. 
 
PPUD records details of all indeterminate sentence prisoners at the point of 
conviction, those engaged in the Generic Parole Process and prisoners 
(determinate and indeterminate) who have been recalled from licence. It 
also covers those who have received a restricted hospital order/direction 
from a Crown Court, and those remand and convicted prisoners who have 
been transferred from prison/detention centres to psychiatric hospital under 
the relevant sections of mental health legislation. 
 
All decisions taken by the NOMS casework sections and the Parole Board 
are recorded on the system. 
 
Personal information recorded includes (but is not limited to) name, date of 
birth, gender, identifying numbers, ethnicity, last known address, probation 
area and sentencing information. 
 
OMPPG and the Parole Board run monthly and ad hoc reports to cleanse 
data that are not otherwise identified by data validation routines built into the 
system. 
 
Probation data 
 
Since 2005, detailed information on the supervision of offenders (at the 
individual offender level) has been submitted by probation trusts on a 
monthly basis. These monthly ‘probation listings’ include information on 
offenders starting probation supervision. Between 2002 and 2005, this 
information was submitted quarterly, and prior to 2002 a different data 
 
18

 
collection system was in place, which meant that information on caseload 
had to be calculated based on the number of people starting supervision 
and the number of terminations. 
 
The quality of the information recorded on the probation data is generally 
assumed to be relatively high as it is a direct extract from an operational 
system upon which the probation service depends for managing offenders 
locally. The extract consists of a small number of key fields for which 
completion is mandatory. Probation trusts have their own IT departments 
which manage their own data validation processes and when the data is 
received centrally it is subject to another set of data validation processes. 
Trends from the data are consistent with comparable time-series from the 
Courts Proceeding Database. Any large scale recording systems are 
subject to possible errors with data entry and processing, but there are no 
known issues regarding the probation commencements data. 
 
Identification of drug-misusing offenders 
 
There are four ways a drug-misusing offender can be identified: 
 
 Individuals who have tested positive for heroin or crack/cocaine 
following an arrest or charge for ‘trigger’ offences (largely acquisitive 
crime offences) as part of the Drug Interventions Programme (DIP) 
are included as adult proven offenders. 
 
  Any offender that received an OASys assessment whilst on licence 
or on a community sentence and are either recorded as being subject 
to a current Drug Treatment and Testing Order (DTTO) or Drug 
Rehabilitation Requirement (DRR), or are assessed as having a 
criminogenic drug need. 
 
  Any offender identified as requiring further drug interventions by 
Counselling, Assessment, Referral, Advice, Throughcare (CARAT) 
teams in prison, and now being released into the community. 
 
  Any offender identified by local Criminal Justice Integrated Teams 
(CJITs) as requiring further intervention for their drug use and 
offending as part of DIP. 
 
Drug Interventions Programme 
The Drug Interventions Programme (DIP) was introduced in April 2003 with 
the aim of developing and integrating measures for directing adult drug-
misusing offenders into drug treatment and reducing offending behaviour. 
The programme comprises of a number of interrelated interventions: 
 
 Drug testing in police custody for specified Class A drugs – heroin, 
cocaine and crack cocaine – for individuals arrested for trigger 
offences (primarily offences related to acquisitive crime). 
 
 
19

 
 Assessment following a positive test to establish the extent of the 
individual’s drug-misuse, and whether the individual might benefit 
from further assessment, assistance or treatment. 
 
 Conditional cautioning which may include a DIP drug rehabilitative 
condition, tailored to the offender’s drug use and offending. 
 
 Restriction on bail for adults who have tested positive and whose 
offence is a drug offence or is drug-related. 
 
 CJITs manage offenders who have been referred to treatment and 
co-ordinate agencies and services so they offer access to joined-up 
treatment and support. They maintain strong links with both the 
National Probation Service and Prison Service to ensure the 
continuity of care whilst the offender is within the Criminal Justice 
System. 
 
Legislative changes have broadened the scope of the programme: 
 
 A major expansion of DIP took place in April 2006 to move the point 
of drug testing from the point of charge to the point of arrest and to 
introduce required (rather than voluntary) assessments. This change 
broadened the scope and size of the cohort coming into contact with 
DIP. 
 
 The latest changes took effect from April 2011, when the 
authorisation to conduct drug testing on arrest was extended across 
England and Wales. Drug testing on arrest previously occurred only 
in ‘intensive’ DIP areas, which had high levels of acquisitive crime. 
 
Data sources 
Records of those who test positive are logged onto the Drugs Intervention 
Management Information System (DIMIS), which is managed by the Home 
Office. An extract of positive drug test records for the relevant period is used 
for a match to the PNC. 
 
Offenders identified as drug-misusers via CARAT teams and CJITs are also 
recorded onto DIMIS, from which an extract is taken for the relevant period 
to match to the PNC. OASys records are collated centrally within the 
Ministry of Justice in the OASys Data, Evaluation and Analysis Team (O-
DEAT) database, from which an extract is taken for the relevant period to 
match to the PNC. 
 
Identification of prolific and other priority offenders 
 
The Prolific and other Priority Offenders Programme (PPO) aims to use a 
multi-agency approach to focus on a very small, but hard core group of 
prolific/persistent offenders who commit disproportionate amounts of crime 
and cause disproportionate harm to their local communities. Full 
implementation of all three strands had commenced by the beginning of 
February 2005. In 2009, all local areas were asked to review their PPO 
 
20

 
schemes to ensure that the programme remained squarely focused on 
those offenders that were of most concern to the communities in which they 
live. 
 
The identification of a PPO is undertaken at a local level involving police, 
local authorities, prison and probation services and youth offending teams. 
The factors that influence the decision of whether an offender is included in 
the PPO programme are: 
 
 the nature and volume of crimes they commit; 
 
 the nature and volume of other harm they cause; and 
 
 the detrimental impact they have on their community. 
 
This process will typically involve police, prison and probation information 
systems and other tools available. 
 
The size of the PPO caseload at a local level is influenced by a range of 
factors, including the number of offenders who meet the locally agreed 
selection criteria and the capacity of local partner agencies to provide the 
intensive management of offenders under PPO supervision. 
 
PPO cohort data are derived from JTRACK, which is a management 
information and tracking tool used by practitioners in various criminal justice 
agencies to record details of the offenders being managed as PPOs in a 
local area. JTRACK relies on the accurate input of data by local users to 
ensure that the details of the caseload on the system reflect the caseload 
being managed. An extract of the caseload from JTRACK is taken for the 
relevant period to match to the PNC. 
 
Young offenders in secure accommodation 
 
Information about secure training centres (STCs) and secure children’s 
homes (SCHs) comes from the Youth Justice Board's (YJB) Secure 
Accommodation Clearing House System (SACHS) database. The under 18 
year olds in Young Offender Institutes (YOIs) is also from SACHS, whereas 
information about young people aged 18 and held in YOIs is supplied by the 
Prison Service and private YOIs. 
 
The quality of the information recorded on the SACHS database is generally 
assumed to be relatively high as it is a direct extract from an operational 
system which is used to place young people in custody. The extract uses a 
number of key fields for which completion is mandatory when booking a 
young person into custody. 
 
Data processing and analysis 
 
The data underpinning the results are considered by Ministry of Justice to 
be broadly robust. Considerable work has been carried out ensuring data 
 
21

 
quality, and the data have been used for research publications. Scrutiny of 
the data source continues in order to ensure the data remains reliable. 
 
The National Audit Office (NAO) identified risk factors in its review of the 
reporting of PSA targets (NAO, 2005). The remainder of this section 
addresses these. 
 
Matching offender records 
 
This process involves matching data on prison discharges and court order 
commencements to the PNC database. The process uses automated 
matching routines that look at offenders’ surnames, initials, and dates of 
birth, using direct name matching along with a variety of ‘sounds like’ 
algorithms. The matching algorithm also searches through PNC held 
information on alias names and dates of birth for offenders. However, not all 
offenders are matched and a thorough analysis of bias in the matching 
system has yet to be undertaken. Table 2 below shows that the overall 
matching rates between 2000 and 2010 have remained high. 
 
Table 2: Matching rates for the different data sources for 2000, 2002 to 
2010 cohorts 
2000
2002
2003
2004
2005
2006
2007
2008
2009
2010
Prison
Prison discharges
87,083
87,338
85,920
86,970
84,897
83,725
87,340
95,824
94,114
91,044
Automatically matched to the PNC
80,572
81,211
80,121
81,125
79,398
78,285
81,874
90,021
88,745
87,845
Matched to an index date
73,810
75,121
73,327
73,390
71,246
68,185
69,741
76,668
74,189
65,278
Percentage matched to the PNC
92.5%
93.0%
93.3%
93.3%
93.5%
93.5%
93.7%
93.9%
94.3%
96.5%
Percentage matched to the PNC and index 
offences (not breach etc.)
84.8%
86.0%
85.3%
84.4%
83.9%
81.4%
79.9%
80.0%
78.8%
71.7%
Court Orders
Court order starts
136,023
154,621
158,750
164,831
163,681
176,346
187,386
189,643
191,784
186,417
Automatically matched to the PNC
123,540
142,838
148,257
154,075
158,416
172,906
184,740
187,253
190,128
185,112
Matched to an index date
105,685
115,108
119,446
122,927
130,307
148,072
159,279
163,519
167,378
164,579
Percentage matched to the PNC
90.8%
92.4%
93.4%
93.5%
96.8%
98.0%
98.6%
98.7%
99.1%
99.3%
Percentage matched to the PNC and index 
offences (not breach etc.)
77.7%
74.4%
75.2%
74.6%
79.6%
84.0%
85.0%
86.2%
87.3%
88.3%
YJB
YJB discharges
-
1,337
1,612
1,521
1,551
1,564
1,553
1,647
1,626
1,770
Automatically matched to the PNC
-
1,226
1,502
1,425
1,448
1,464
1,463
1,537
1,564
1,682
Matched to an index date
-
680
818
785
800
769
780
845
817
916
Percentage matched to the PNC
-
91.7%
93.2%
93.7%
93.4%
93.6%
94.2%
93.3%
96.2%
95.0%
Percentage matched to the PNC and index 
offences (not breach etc.)
-
50.9%
50.7%
51.6%
51.6%
49.2%
50.2%
51.3%
50.2%
51.8% 
 
The total number of offenders matched to the PNC is substantially higher 
than the final figure for the cohorts – for example, in 2010 there were 
274,639 matched offenders, but a final cohort size of 230,773. The main 
reasons for these discrepancies are: 
 
 Conviction dates for the beginning of the community, suspended or 
custodial sentence do not match the conviction date within seven 
days of the criminal records from the PNC database; 
 The index offence was not dealt with by a Home Office police force – 
this ensures that only offences in England and Wales are counted; 
 Exclusion of all offenders where the index offence is a breach, since 
we are only interested in new offences; and 
 
22

 
 Exclusion of multiple offender entries (see section above titled 
“Multiple offender entries” for further details). 
 
Counting rules 
 
The counting rules for choosing which prison discharges to include offer a 
variety of choices. For instance, it makes little sense to include offenders 
deported on release or who have died. These counting rules were 
enumerated and discussed to ensure a more accurate and consistent count 
and are reviewed on an annual basis to ensure a consistent approach. 
 
Complexity of data processing and analysis 
 
The data processing involved for measuring re-offending is complex. To 
analyse re-offending behaviour by previous offending or disposal history 
requires the extraction of criminal histories that can span a number of 
decades, and the subsequent matching of these histories against the 
probation caseload files and prison discharges in order to generate a 
dataset. 
 
The extraction of the criminal histories 
 
To quality assure the extraction of criminal histories, a small set of random 
samples of offenders was taken after the analysis to check, via a basic 
validation, that outputs of the SQL (Structured Query Language) program 
were accurate. The Ministry of Justice is confident that this process has 
been successful. 
 
Level of subjectivity 
 
There is relatively little subjectivity in the system. Occasional judgements 
are required (e.g. where to classify an offence), but these will not 
significantly influence the results. 
 
Maturity and stability of the data system 
 
The system is well established having been used a number of times to 
produce re-offending statistics for publication. Nonetheless, vigilance 
continues to be exercised to ensure the validity of the results. 
 
Expertise of those who operate the system 
 
Prison and court order data-feeds are continually monitored and 
improvement work is regularly undertaken to improve the reliability and the 
accuracy of datasets. The internal processing of the results within the 
Ministry of Justice has been subject to dip sampling of criminal histories and 
the statistical model has been extensively tested. 
 
 
23

 
Interpreting trends in the proportion of offenders who 
commit a serious re-offence against the person 
 
Care should be taken when interpreting the severity rate for the following 
reasons: 
 
 Time through the Criminal Justice System – more serious 
offences are likely to take a longer time to progress through the 
Criminal Justice System than less serious offences. The proven re-
offending statistics track proven re-offending behaviour for a year 
upon offenders entering the cohort, plus an additional six months for 
convictions to be updated on the system. There is a risk that this time 
scale is not long enough to capture the most serious offences. 
However, analysis suggests that the number of serious proven re-
offences picked up by the measure remains comparatively stable 
year on year, ensuring performance is comparable over time. 
 Reporting variation – variation in reporting time between police 
force areas and courts may also have an impact on how many 
serious offences are captured during the one year follow-up period. 
Data on historical trends 
 
The data used to measure proven re-offending is from the PNC. Police 
forces started to enter criminal records locally in 1995. In order to allow time 
for good practice among police forces in entering data onto the PNC to 
become embedded, PNC data was used to measure proven re-offending for 
the first time in 2000. In the headline bulletin, results are compared to 2000 
to highlight long-term trends because it is the earliest data on proven re-
offending that exists on a comparable basis. Results prior to 2000 cannot be 
compared to results from 2000 onwards for two main reasons: 
 
 Change in data source – re-offences are measured using data from 
the PNC (which covers recordable offences), whereas data from 
years before 2000 were measured using the offenders index (which 
covered a narrower range of offences). 
 Change in measurement – the concept being measured from 2000 
onwards in these reports is that of using the offence date to measure 
re-offences (a period of time is allowed for offences to be committed, 
and a further period allowed for these offences to be proved by 
caution, reprimand, final warning or court conviction), whereas the 
concept being measured prior to 2000 was that of using the 
conviction date to measure re-convictions (any conviction occurring 
in a set period of time, whether or not the offence occurred in that 
time period). 
 
However the ‘Compendium of Re-offending Statistics and Analysis 2010’, 
published in November 2010, provides the most consistent statistical series 
possible between 1971 and 2006, adjusting for known methodological 
changes. For more information, please refer to Chapter 4.4 at the following 
link: 
 
24

 
 
www.justice.gov.uk/statistics/reoffending/compendium-of-reoffending-
statistics-and-analysis 
 
Results for 2001 cannot be calculated for offenders on court orders because 
of a problem with archived data on court orders. 
Local breakdowns of the headline proven re-offending rates are available 
from 2005 onwards. Proven re-offending data are broken down by locality 
using the address and post-code information of the offender. Where this 
information is missing, the location of the processing police force is used 
instead. This is not a completely reliable indicator of the offender’s home 
address as offenders may offend in a different locality than where they 
reside. The completeness of this information has improved over time. In 
2000, this information was omitted for 29 per cent of cases, which was 
considered too high to produce reliable results. By 2005, this was reduced 
to 16.5 per cent, and there has been a continuing downward trend since 
then. 
 
25

 
Statistical modelling and coefficients 
Introduction 
 
The characteristics of proven offenders are likely to be systematically 
different over time and by sentence type as the Criminal Justice System 
targets particular sentences to offenders most likely to benefit from that 
type. It is therefore important to note that it is not possible to reach firm 
conclusions about changes in rates over time, nor about the relative 
effectiveness of different sentence types, from actual proven re-offending 
rates. 
 
The Ministry of Justice has developed models to address these two issues: 
 
 modelling to adjust the baseline to reflect changes in offender 
characteristics (see below). 
 
 modelling to match offenders across sentence types to make valid 
comparisons. Refer to the ‘Compendium of Re-offending Statistics 
and Analysis 2011’ at the link below for this analysis: 
 
www.justice.gov.uk/statistics/reoffending/compendium-of-reoffending-
statistics-and-analysis 
 
Modelling to adjust for the varying composition of the cohort 
of offenders over time 
If the composition of the cohorts of offenders being compared differs 
significantly over time so that the type of offenders in one year is inherently 
more (or less) likely to re-offend, this may result in an apparent rise or fall in 
the proven re-offending rates even when there may be no ‘real’ difference 
for similar offenders over that time. In order to address this problem, we 
have adopted the following solution: 
 
 modelling the likelihood of proven re-offending based on known 
offender characteristics using historic data (which will be defined as 
the baseline); 
 
 identifying the characteristics of the most recent cohort; 
 
 using the model, adjusting the baseline proven re-offending rate to 
match these characteristics; and 
 
 comparing this adjusted rate with the current rate to make a more 
realistic estimate of trends over time. 
 
In previous publications of proven re-offending statistics, this approach has 
been referred to as the predicted rate of proven re-offending. 
 
26

 
 
 
 
Statistical model 
 
The 2008 statistical model is an update and improvement on the 2000 and 
2005 logistic regression models and includes a range of offender 
characteristics available from the PNC, such as age, gender, offence group 
and criminal history. 
 
The logistic regression model based on the 2008 data identifies a 
statistically significant set of variables that are related to proven re-offending 
and based on these provides a probability of proven re-offending for each 
offender. However, other factors, for which data on these samples are not 
available, such as drug and alcohol use, employment, accommodation and 
marital background are likely to be significantly related to re-offending. 
 
This means that the adjusted proven re-offending rates are only valid for 
terms included in the final model. Any adjusted proven re-offending rates for 
groups of offenders that have a common characteristic that is not in the final 
model (e.g. employment status or disposal type) can suffer from statistical 
biases and are, therefore, unreliable. 
 
For the 2008 model additional developments were included to ensure that 
the adjusted rate model was a more parsimonious model, more robust 
against changes in the number of offenders, and that interaction terms and 
non-linear terms were included where appropriate. The final decision for 
inclusion or exclusion of particular variables was heavily influenced by their 
statistical significance (typically p < 0.10). 
 
The Ministry of Justice believes that the method used for the construction of 
the statistical model for producing adjusted rates is robust and fit for 
purpose. 
 
Variables included 
 
The following notes provide some further detail on the 2008 model and 
show the relative impacts of different variables when holding all other 
variables constant. 
 
Gender 
Gender is included in the model as a categorical variable separating out 
males and females. Generally, males are more likely to commit a proven re-
offence than females. 
 
Age 
Age is included in the model for adults as a linear, quadratic and cubed term 
and is included for juveniles as a categorical variable separating offenders 
into seven age bands. Generally, younger adults are more likely to commit a 
proven re-offence than older adults, and older juveniles are more likely to 
re-offend than younger juveniles. 
 
 
27

 
Index offence 
The index offence represents the offence that led to the offender entering 
the cohort. Index offences were classified into 21 broad categories and their 
relative coefficients are shown in relation to the reference category 
‘violence’. To ensure the reliability and replicability of the model coefficients, 
any index offences with low numbers were grouped with the ‘other’ index 
offence group. 
 
Ethnicity 
Ethnicity is derived from the PNC and reflects the officer’s view of the 
offender’s ethnicity. Thus, ethnicity in this model should be taken as a proxy 
for the actual ethnicity and the results should not be over-interpreted 
because any biases in the assessment are unknown. Ethnicity was a 
statistically significant factor, making it an important factor to control for and, 
therefore, it was included in the model. 
 
Copas rate 
The Copas rate (Copas and Marshall, 1998) controls for the rate at which an 
offender has built up convictions throughout their criminal career. The higher 
the rate, the more convictions an offender has in a given amount of time, 
and the more likely it is that an offender will be re-convicted. 
The Copas rate formula is: 
 









10
 
 
years
in 
career 
 
criminal
 
of
Length 
1
 
cautions
or 
 s
appearance
court 
 
of
Number 
log
 
rate
 
copas
e
 
 
For adults the Copas rate is included as a linear and quadratic, but for 
juveniles it is included as a linear term only. As mentioned above, inclusion 
of variables was heavily influenced by their statistical significance. 
 
Length of criminal career 
An offender’s criminal career is a significant factor in predicting the 
likelihood of a re-offence and this relationship is quadratic, thus both linear 
and quadratic terms were included in the model. 
 
Total number of previous offences 
The total number of previous offences is a significant factor in predicting the 
likelihood of re-offending. The previous offending variables counted cautions 
and convictions and were included as linear and logged variables. 
 
Previous custodial sentences 
For adults, the number of previous custodial sentences was implemented as 
a continuous variable in both linear and quadratic terms. For juveniles, 
previous custodial sentences were included as a binary term: had the 
offender received one or more previous custodial sentences, yes or no. The 
difference in treatment reflects the more limited custodial history juvenile 
offenders generally possess compared to adult offenders. 
 
Counts of previous offending by type of offence 
For adults, the number of previous offences by type of offence was an 
improvement over simple yes/no variables for recording the presence of 
 
28

 
prior offences in the relevant categories. For juvenile offenders, simple 
yes/no variables for recording the presence of prior offences in the relevant 
categories performed better. The difference in treatment reflects the more 
limited offending history juvenile offenders generally possess compared to 
adult offenders. 
 
Interaction terms 
Interaction terms are calculated by multiplying two factors together. The 
inclusion of these terms allows the effect of one variable to vary according 
to the values of another, improving the quality of predictions. This is 
important because three factors (gender, age and total number of previous 
offences) are not completely independent of each other. 
 
For adults, interaction terms were also included for drug-misusing offenders 
as they showed some trends in their proven re-offending behaviour that 
were different from the more general offending population. 
 
Model assessment 
 
The model is assessed by calculating the level of discrimination between 
offenders that committed a proven re-offence and offenders that did not. 
The adult logistic regression model achieved a 78.9 per cent overall 
discrimination level on the 2008 cohort and 72.4 per cent for the juvenile 
logistic regression model. A level of discrimination of about 70 per cent was 
deemed to be acceptable and the model should predict results accurately 
enough for the predicted rate to be used. The discrimination can also be 
evaluated by calculating the Area Under Curve (AUC) for the Receiver 
Operator Characteristic curve. Again, the value for the model was 0.784 for 
the adult regression model in 2008 and 0.716 for the youth regression 
model which means a satisfactory level of discrimination (Hosmer and 
Lemeshow, 2000, p.162). 
 
Coefficients of the 2008 statistical model 
 
The following tables (3 and 4) show the parameter estimates for the various 
components of the logistic regression model for the predicted one year 
proven re-offending rates for adults and young offenders. 
  
Each logistic coefficient is multiplied by the variable value for each offender 
to calculate a linear prediction. To calculate each offender’s predicted 
probability of committing a proven re-offence in the follow-up period or a 
further six month waiting period we transform the linear prediction Z using 
the following formula: 
 
)
exp(
1
)
exp(
g
Reoffendin
 
of
y 
Probabilit
 
Predicted
Z
Z


 
 
The exponent of the coefficient is the odds ratio of committing a proven re-
offence corresponding to the particular coefficient and enables us to make 
comparisons between different categories. For factors with interactions (e.g. 
age and gender) the interpretation is more complex. 
 
29

 
 
The significance (p-value) gives us an assessment of how significant each 
variable is in predicting the likelihood of an offender to commit a proven re-
offence within one year. For modelling purposes, a probability value (p-
value) of less than 0.05 is considered to be significant. 
 
Table 3: List of variables in the logistic regression model applied to 
the 2008 data on adult offenders and their respective coefficients 
 
 
Variables
Coefficient
Logs-odd 
ratios
P-value
Variables
Coefficient Logs-odd 
ratios
P-value
Constant
1.940
6.958
0.000
Index offence:
Violence
Gender:
Robbery
-0.361
0.697
0.000
Female 
Theft
0.482
1.620
0.000
Male
0.645
1.906
0.000
Handling
0.173
1.189
0.000
Taking and driving away
0.180
1.198
0.000
Age:
Sexual child
-0.465
0.628
0.000
Age
-0.250
0.779
0.000
Public order
0.220
1.247
0.000
Age squared
0.006
1.006
0.000
Soliciting/prostitution
0.253
1.288
0.000
Age cubed
-0.00004
1.000
0.000
Domestic burglary
0.148
1.159
0.000
Male * age interaction
-0.013
0.988
0.000
Other burglary
0.337
1.401
0.000
Theft from vehicles
0.478
1.612
0.000
General criminal career variables:
Drink driving
-0.154
0.857
0.000
Previous offences
-0.006
0.994
0.000
Criminal damage 
0.226
1.254
0.000
Previous offences (logged)
0.391
1.478
0.000
Drug supply
-0.400
0.670
0.000
Male * previous offences interaction
-0.003
0.997
0.000
Drug possession
0.074
1.077
0.000
Previous prison sentences
0.045
1.046
0.000
Drug test
-1.167
0.311
0.000
Previous prison sentences (logged)
-0.060
0.942
0.000
Fraud/forgery
-0.213
0.808
0.000
Career length
-0.0001
1.000
0.000
Absconding and bail 
0.364
1.440
0.000
Career length squared
0.000
1.000
0.069
Copas rate
0.385
1.469
0.000
Number of previous offences:
Copas rate squared
-0.064
0.938
0.000
Public order
0.052
1.053
0.000
PPO offender
0.528
xx-xxxx-xxxx
0.000
Sexual
0.035
1.036
0.000
Drug-misusing offender
1.422
4.146
0.000
Domestic burglary
-0.006
0.994
0.005
Theft
0.012
1.012
0.000
Ethnicity: 
Handling
-0.010
0.990
0.002
White
Absconding and bail 
0.018
1.018
0.000
Unknown 
-0.663
0.516
0.000
Taking and driving away
-0.007
0.993
0.003
White other
0.324
1.383
0.000
Criminal damage 
0.017
1.017
0.000
Black
0.161
1.175
0.000
Drug supply
-0.044
0.957
0.000
Pacific 
0.210
1.233
0.000
Drug possession
0.013
1.013
0.000
Middle East
0.130
1.138
0.003
Other 
-0.002
0.998
0.073
Interaction with drug-misusing 
offenders: 
Previous offences (logged)
-0.156
0.855
0.000
Index offence of drug supply
-0.430
0.651
0.000
Index offence of drug 
possession
-0.550
0.577
0.000
Reference category
Reference category
Reference category
 
 
30

 
Table 4: List of variables in the logistic regression model applied to 
the 2008 data on young offenders and their respective coefficients 
 
Variables
Coefficient
Logs-odd 
ratios
P-value
Variables
Coefficient
Logs-odd 
ratios
P-value
Constant
-1.495
0.224
0.000
Index offence:
Violence
Gender:
Robbery
0.130
1.139
0.003
Female 
Public order or riot
0.178
1.195
0.000
Male
0.527
xx-xxxx-xxxx
0.000
Sexual offences
-0.578
0.561
0.000
Sexual offences against children
-1.157
0.314
0.000
Age:
Domestic burglary
0.233
1.262
0.000
Aged 10-11
Other burglary
0.083
1.087
0.026
Aged 12
0.354
1.425
0.000
Theft
-0.088
0.916
0.000
Aged 13
0.448
1.566
0.000
Handling
0.118
1.126
0.018
Aged 14
0.431
1.538
0.000
Fraud or forgery
-0.251
0.778
0.000
Aged 15
0.186
1.205
0.000
Absconding or bail offences
0.176
1.192
0.022
Aged 16
-0.124
0.883
0.017
Taking and driving away
0.116
1.123
0.003
Aged 17
-0.202
0.817
0.000
Theft from vehicles
0.264
1.302
0.000
Drunk driving
-0.488
0.614
0.000
Interactions between age and gender:
Female at any age
Any previous offences:
Male aged 10-11
Violence
0.039
1.039
0.062
Male aged 12
-0.276
0.759
0.000
Robbery
0.101
1.106
0.011
Male aged 13
-0.214
0.807
0.000
Public order or riot
0.143
1.154
0.000
Male aged 14
-0.157
0.855
0.000
Domestic burglary
0.166
1.181
0.000
Male aged 16
0.134
1.144
0.002
Other burglary
0.099
1.104
0.001
Male aged 17
0.113
1.120
0.013
Theft
0.135
1.144
0.000
Handling
0.107
1.113
0.009
General criminal career variables:
Absconding or bail offences
0.096
1.101
0.032
Career length
0.000
1.000
0.000
Taking and driving away
0.088
1.093
0.012
Career length squared
0.000
1.000
0.000
Theft from vehicles
0.125
1.133
0.012
Copas rate
0.128
1.137
0.001
Drunk driving
-0.245
0.783
0.033
Previous offences
-0.036
0.964
0.000
Criminal or malicious damage
0.069
1.071
0.001
Previous offences (logged)
0.920
2.510
0.000
Other
0.138
1.148
0.001
Previous prison sentence(s)
0.124
1.132
0.022
Miscellaneous
-0.689
0.502
0.014
PPO offender
0.930
2.534
0.000
Breaches
0.762
2.144
0.007
Ethnicity: 
White
Unknown
-0.823
0.439
0.000
White (other)
0.196
1.217
0.000
Black
0.187
1.206
0.000
Asian
-0.200
0.819
0.000
Pacific
-0.468
0.626
0.001
Reference category
Reference category
Reference category
Reference category
Reference category
Reference category
 
31

 
Additional modelling for prison performance 
 
Assessing the performance of individual prisons in reducing re-offending is 
difficult because the particular characteristics of offenders that are at a 
particular prison are likely to be the main drivers behind re-offending. 
 
A statistical methodology has been developed to examine prison re-
offending rates that not only takes account of offence and offender 
characteristics, but also takes account of the hierarchical structure of the 
data, i.e. that offenders are within prisons. 
 
Two separate models were developed: for prisoners receiving sentences of 
fewer than 12 months and prisoners with sentences of 12 months or over. 
The separate models for prisoners with sentences of fewer than 12 months 
and 12 months or more reflects differences in prisoners’ re-offending 
behaviour by prison sentence length. 
 
The model used for both types of offender was a logistic regression model 
with mixed effects (fixed and random). The outcome variable is a binary 
yes/no variable representing whether an offender re-offends or not. 
Offender characteristics are included as fixed independent variables and the 
prisons are included as a random effect component which allows each 
prison to interact with the fixed effects differently. 
 
The variables included in the model were similar to those used to develop 
the adjusted baseline described above: age, ethnicity, index offence, 
previous offences, previous prison sentences, Copas scores, and criminal 
career, as well as the random effects component of prisons. The goodness-
of-fit by AUC was satisfactory, above 0.77 in all cases. 
 
Considerable preliminary analysis has been undertaken investigating the 
relative important of offence, offender and prison level variables in 
explaining custodial re-offending. This analysis has overwhelmingly shown 
that offence and offender level variables shape re-offending whereas prison-
level variables refine re-offending behaviour. For this reason, the model 
uses offender and offence level variables and only models prison level 
effects using a single random effects component. 
 
This model generates an expected probability of re-offending for each 
offender. When aggregated up to the prison it produces an expected 
proportion of offenders who re-offend. This can be compared with the actual 
rate of re-offending. 
 
Where the model-predicted re-offending rate was statistically significantly 
different to actual re-offending rates, two possible explanations are 
plausible: 
 
1. Missing characteristics: it is possible that there are underlying 
offence, offender or prison characteristics affecting re-offending 
behaviour that are not included in the current model; or 
 
32

 
2. A genuine difference: there is something specific to these prisons 
that make them better/worse than predicted. 
 
Additional modelling for probation performance 
Results in the headline measure are compared to a baseline rate, adjusted 
for changes in the offender profile. This relies on an estimate of the 
relationship between offender characteristics and proven re-offending 
behaviour over 12 months. An equivalent estimate has been carried out for 
the proven re-offending behaviour specifically of offenders commencing 
court orders. This uses the same variables as the headline measure plus 
additional variables to ensure that the actual and predicted rates are 
identical for every probation trust in the baseline period (2008). The tables 
accompanying the report present the adjusted baseline for each trust. 
 
Differences between the prison and probation trusts models and the 
model for the adjusted baseline for the headline measure 
 
 The adjusted baseline for the headline measure applies to all 
offenders; the prison and probation models only apply to offenders 
discharged from custody or given a court order. 
 
 The adjusted baseline for the headline measure is created using a 
fixed effects model using only offender and offence level variables; 
the probation model does the same, but the prison models use 
offender and offence level variables and also include a random 
component to reflect that prisoners are located within prisons. 
 
 The adjusted baseline for the headline measure and for the probation 
model is derived using data from a baseline year (2008). The 
observed re-offending is equal to the predicted re-offending for the 
baseline year; the model coefficients are then applied to subsequent 
years and the predicted rates begins to differ from the actual rates. 
Provided the baseline year model is frequently refreshed, this 
ensures that any deviations of the actual re-offending rate from the 
predicted rate are due to system changes and not due to changes in 
the cohort make up. This approach enables us to assess progress in 
reducing re-offending. Whereas, the prison model is generated from 
scratch every year and assesses if any prison differs from the 
national average. As with the previous approach, the observed re-
offending rate is still equal to the predicted re-offending for the prison 
population as a whole. It will not necessarily be the case for individual 
prisons. This approach provides an idea of which prisons have 
significantly lower (or higher) re-offending rates than predicted. 
 
 Work is underway to develop an equivalent model for probation trusts 
to the one used for prisons. 
 
33

 
Appendix A: List of serious offences 
Serious violence against the person 
1.  Murder: 
1. 
Of persons aged 1 year or over. 
2. 
Of infants under 1 year of age. 
 
2. 
Attempted murder. 
 
4. 
Manslaughter, etc: 
1. 
Manslaughter. 
2. 
Infanticide. 
3. 
Child destruction. 
 
 
   
 
 
 
5. 
Wounding or other act endangering life: 
1. 
Wounding, etc. with intent to do grievous bodily harm, etc. or to resist 
apprehension. 
2. 
Shooting at naval or revenue vessels. 
4. 
Attempting to choke, suffocate, etc. with intent to commit an indictable offence 
(garrotting). 
5. 
Using chloroform, etc. to commit or assist in committing an indictable offence. 
6. 
Burning, maiming, etc. by explosion. 
7. 
Causing explosions or casting corrosive fluids with intent to do grievous bodily 
harm. 
8. 
Impeding the saving of life from shipwreck. 
9. 
Placing, etc. explosives in or near ships or buildings with intent to do bodily 
harm, etc. 
10. Endangering life or causing harm by administering poison. 
11. Causing danger by causing anything to be on road, interfering with a vehicle or 
traffic equipment. 
13. Possession, etc. of explosives with intent to endanger life. 
14. Possession of firearms, etc. with intent to endanger life or injure property, etc. 
(Group I). 
15. Possession of firearms, etc. with intent to endanger life or injure property, etc. 
(Group II). 
16. Possession of firearms, etc. with intent to endanger life or injure property, etc. 
(Group III). 
17. Using, etc. firearms or imitation firearms with intent to resist arrest, etc. (Group 
I). 
18. Using, etc. firearms or imitation firearms with intent to resist arrest, etc. (Group 
II). 
19. Using, etc. firearms or imitation firearms with intent to resist arrest, etc. (Group 
III). 
 
[Group I - Firearms, etc. other than as described in Group II or III. 
 
Group II - Shotguns as defined in s.1 (3)(a) of the Firearms Act 1968. 
 
Group III - Air weapons as defined in s.1 (3)(b) of the Firearms Act 1968] 
20. Use etc. of chemical weapons. 
21. Use of premises or equipment for producing chemical weapons. 
22. Use, threat to use, production or possession of a nuclear weapon. 
23. Weapons related acts overseas. 
24. Use of noxious substances or things to cause harm or intimidate. 
25. Performing an aviation function or ancillary function when ability to carry out 
function is impaired because of drink or drugs. 
26. Endangering safety at sea/aerodromes. 
27. Torture. 
 
8. 
Other wounding, etc.: 
1. 
Wounding or inflicting grievous bodily harm (inflicting bodily injury with or without 
weapon).  
 
34

 
33. Racially aggravated wounding or inflicting grievous bodily harm (inflicting bodily 
injury with or without weapon). 
40. Religiously aggravated malicious wounding or GBH. 
46. Racially or religiously aggravated malicious wounding or grievous bodily harm. 
 
Sexual offences 
17. Sexual assault on a male (previously indecent assault on a male): 
11. Indecent assault on male person under 16 years. 
12. Indecent assault on male person 16 years or over. 
13. Assault on a male by penetration. 
14. Assault of a male child under 13 by penetration. 
15. Sexual assault on a male. 
16. Sexual assault of a male child under 13. 
 
19. Rape: 
2. 
Man having unlawful sexual intercourse with a woman who is a defective. 
3. 
Male member of staff of hospital or mental nursing home having unlawful sexual 
intercourse with female patient. 
4. 
Man having unlawful sexual intercourse with mentally disordered female patient 
who is subject to his care. 
7. 
Rape of a female aged under 16. 
8. 
Rape of a female aged 16 or over. 
9. 
Rape of a male aged under 16. 
10. Rape of a male aged 16 or over. 
11. Attempted rape of a female aged under 16. 
12. Attempted rape of a female aged 16 or over. 
13. Attempted rape of a male aged under 16. 
14. Attempted rape of a male aged 16 or over. 
16. Rape of female child under 13 by a male. 
17. Rape of a male child under 13 by a male. 
18. Attempted rape of a female child under 13 by a male. 
19. Attempted rape of a male child under 13 by a male  
 
20. Sexual assault on female (previously indecent assault on a female): 
1. 
On females under 16 years of age. 
2. 
On females aged 16 years and over. 
3. 
Assault on a female by penetration. 
4. 
Assault on a female child under 13 by penetration. 
5. 
Sexual assault on a female. 
6. 
Sexual assault on a female child under 13. 
 
21. Sexual activity (male and female) (including with a child under 13) (previously unlawful 
intercourse with a girl under 13): 
2. 
Causing or inciting a female child under 13 to engage in sexual activity - 
penetration. 
3. 
Causing or inciting a female child under 13 to engage in sexual activity - no 
penetration. 
4. 
Causing or inciting a male child under 13 to engage in sexual activity - 
penetration 
5. 
Causing or inciting a male child under 13 to engage in sexual activity - no 
penetration. 
6. 
Sexual activity with a female child under 13 - offender aged 18 or over - 
penetration. 
7. 
Sexual activity with a male child under 13 - offender aged 18 or over - 
penetration. 
8. 
Causing or inciting a female child under 13 to engage in sexual activity - 
offender aged 18 or over – penetration. 
9. 
Causing or inciting a male child under 13 to engage in sexual activity - offender 
aged 18 or over - penetration. 
10. Engaging in sexual activity in the presence of a child under 13 (offender aged 
18 or over). 
 
35

 
11. Causing a child under 13 to watch a sexual act (offender aged 18 or over). 
12.   Sexual activity with a female child under 13 - offender aged under 18. 
13.   Sexual activity with a male child under 13 - offender aged under 18. 
14.   Causing of inciting a female child under 13 to engage in sexual activity - 
offender under 18. 
15. Causing or inciting a male child under 13 to engage in sexual activity - offender 
under 18. 
16. Engaging in sexual activity in the presence of a child under 13 - offender under 
18. 
17. Causing a child under 13 to watch a sexual act - offender under 18. 
18. Sexual activity with a female under 13 - offender aged 18 or over - no 
penetration. 
19. Sexual activity with a male child under 13 - offender aged 18 or over - no 
penetration. 
20. Causing or inciting a female child under 13 to engage in sexual activity - 
offender aged 18 or over - no penetration. 
21. Causing or inciting a male child under 13 to engage in sexual activity - offender 
aged 18 or over - no penetration. 
22. Sexual activity with a female child under 13 - offender aged under 18 - no 
penetration. 
23. Sexual activity with a male child under 13 - offender aged under 18 - no 
penetration. 
24. Causing or inciting a female child under 13 to engage in sexual activity - 
offender aged under 18 - no penetration. 
25. Causing or inciting a male child under 13 to engage in sexual activity - offender 
aged under 18 - no penetration. 
 
 22. Sexual activity (male and female) (including with a child under 16) (previously unlawful 
sexual intercourse with a girl under 16): 
0. 
Unlawful sexual intercourse with girl under 16 (offences committed prior to 1 
May 2004). 
2. 
Causing a female person to engage in sexual activity without consent – 
penetration. 
3. 
Causing a male person to engage in sexual activity without consent – 
penetration. 
4. 
Causing a female person to engage in sexual activity without consent - no 
penetration. 
5. 
Causing a male person to engage in sexual activity without consent - no 
penetration. 
6. 
Sexual activity with a female child under 16 (offender aged 18 or over) – 
penetration. 
7. 
Sexual activity with a male child under 16 (offender aged 18 or over) – 
penetration. 
8. 
Causing or inciting a female child under 16 to engage in sexual activity (offender 
aged 18 or over) - penetration 
9. 
Causing of inciting a male child under 16 to engage in sexual activity (offender 
aged 18 or over) – penetration. 
10. Engaging in sexual activity in the presence of a child under 16 (offender aged 
18 or over). 
11. Causing a child under 16 to watch a sexual act (offender aged 18 or over). 
18. Sexual activity with a female child under 16 - offender aged 18 or over - no 
penetration. 
19. Sexual activity with a male child under 16 - offender aged 18 or over - no 
penetration. 
20. Causing or inciting a female child under 16 to engage in sexual activity (offender 
aged 18 or over) - no penetration. 
21. Causing or inciting a male child under 16 to engage in sexual activity (offender 
aged 18 or over) - no penetration. 
 
70. Sexual activity etc. with a person with a mental disorder: 
1. 
Sexual activity with a male person with a mental disorder impeding choice – 
penetration. 
 
36

 
2. 
Sexual activity with a female person with a mental disorder impeding choice – 
penetration. 
3. 
Sexual activity with a male person with a mental disorder impeding choice - no 
penetration. 
4. 
Sexual activity with a female person with a mental disorder impeding choice - no 
penetration. 
5. 
Causing or inciting a male person with a mental disorder impeding choice to 
engage in sexual activity – penetration. 
6. 
Causing or inciting a female person with a mental disorder impeding choice to 
engage in sexual activity – penetration. 
7. 
Causing or inciting a male person with a mental disorder impeding choice to 
engage in sexual activity – penetration. 
8. 
Causing or inciting a female person with a mental disorder impeding choice to 
engage in sexual activity - no penetration. 
9. 
Engaging in sexual activity in the presence of a person with a mental disorder 
impeding choice. 
10. Causing a person with a mental disorder impeding choice to watch a sexual act. 
11. Inducement, threat or deception to procure sexual activity with a person with a 
mental disorder – penetration. 
12. Inducement, threat or deception to procure sexual activity with a person with a 
mental disorder - no penetration. 
13. Causing a person with a mental disorder to engage in sexual activity by 
inducement, threat or deception - penetration. 
14. Causing a person with a mental disorder to engage in sexual activity by 
inducement, threat or deception - no penetration. 
15. Engaging in sexual activity in the presence, procured by inducement, threat or 
deception, of a person with a mental disorder. 
16. Causing a person with a mental disorder to watch a sexual act by inducement, 
threat or deception. 
17. Care workers: Sexual activity with a male person with a mental disorder - 
penetration. 
18. Care workers: Sexual activity with a female person with a mental disorder - 
penetration. 
19. Care workers: Sexual activity with a male person with a mental disorder - no 
penetration. 
20. Care workers: Sexual activity with a female person with a mental disorder - no 
penetration. 
21. Care workers: Causing or inciting sexual activity (person with  a mental disorder) 
- penetration. 
22. Care workers: Causing or inciting sexual activity (person with a mental disorder) 
- no penetration. 
23. Care workers: Sexual activity in the presence of a person with a mental 
disorder. 
24. Care workers: Causing a person with a mental disorder impeding choice to 
watch a sexual act. 
 
71. Abuse of children through prostitution and pornography (previously child prostitution 
and pornography): 
1. 
Arranging or facilitating the commission of a child sex offence. 
2. 
Paying for sex with a female child under 13 - penetration  
3. 
Paying for sex with a male child under 13 - penetration  
4. 
Paying for sex with a female child under 16 - no penetration. 
5. 
Paying for sex with a male child under 16 - no penetration. 
6. 
Paying for sex with a female child aged 16 or 17. 
7. 
Paying for sex with a male child aged 16 or 17. 
8. 
Causing or inciting child prostitution or pornography - child aged 13-17. 
9. 
Controlling a child prostitute or a child involved in pornography - child aged 13-
17. 
10. Arranging or facilitating child prostitution or pornography - child aged 13-17. 
11. Causing or inciting child prostitution or pornography - child under 13. 
12. Controlling a child prostitute or child involved in pornography - child under 13. 
13. Arranging or facilitating child prostitution or pornography - child under 13. 
 
37

 
14. Paying for sex with a female child aged under 16 – penetration. 
15. Paying for sex with a male child aged under 16 – penetration. 
 
72. Trafficking for sexual exploitation: 
1. 
Arranging or facilitating arrival of a person into the UK for sexual exploitation 
(trafficking). 
2. 
Arranging or facilitating travel of a person within the UK for sexual exploitation 
(trafficking). 
3. 
Arranging or facilitating departure of a person from the UK for sexual 
exploitation (trafficking). 
 
Taking and driving away and related offences 
37. Aggravated vehicle taking: 
1. 
Where, owing to the driving of the vehicle, an accident occurs causing the death 
of any person. 
 
Other motoring offences 
4. 
Manslaughter, etc:  
4. 
Causing death by dangerous driving. 
8. 
(Offences) Causing death by careless or inconsiderate driving (Offences due to 
commence in Autumn 2007). 
 
Drink driving offences 
4. 
Manslaughter, etc.: 
6. 
Causing death by careless driving when under the influence of drink or drugs. 
 
Serious acquisitive offences 
 
Burglary 
 
1. Burglary in a dwelling with intent to commit or the commission of an offence 
triable only on indictment. 
2. Burglary in a dwelling with violence or the threat of violence. 
3. Other burglary in a dwelling. 
4. Aggravated burglary in a dwelling (including attempts ). 
 
Robbery  
1. Robbery. 
2. Assault with intent to rob. 
 
Taking and driving away  
1. Aggravated taking where the vehicle was driven dangerously on a road or other 
public place. 
 
2. Aggravated taking where owing to the driving of the vehicle an accident occurred  
causing injury to any person or damage to any property other than the vehicle. 
 
Theft from or of vehicles  
1. Stealing from motor vehicles. 
2. Stealing from other vehicles. 
3. Theft of motor vehicle. 
4. Unauthorised taking of a motor vehicle. 
 
38

 
Appendix B: Glossary of terms 
Re-offending terms 
 
Cohort – this is the group of individuals whose re-offending is measured. 
 
Index offence – the index offence is the proven offence that leads to an 
offender being included in the cohort. 
 
Index disposal – the index disposal of the offender is the type of sentence 
the offender received for their index offence. 
 
Start point (index date) – this is the set point in time from when re-offences 
are measured. 
 
Follow-up period – this is the length of time proven re-offending is 
measured over. 
 
Waiting period – this is the additional time beyond the follow-up period to 
allow for offences committed towards the end of the follow-up period to be 
proved by a court conviction, caution, reprimand or final warning. 
 
Adjusted to baseline – proven re-offending is related to the characteristics 
of offenders which means that any overall rate of proven re-offending will 
depend, in part, on the characteristics of offenders coming into the system 
(just as the examination pass rate of a school will be related to the 
characteristics of its pupils). We use a modelling technique to produce a 
baseline figure adjusted to match the characteristics of the cohort we are 
comparing. 
 
Re-conviction – where an offender is convicted at court for an offence 
committed within a set follow-up period and convicted within either the 
follow-up period or waiting period. 
 
Proven re-offence – where an offender is convicted at court or receives 
some other form of criminal justice sanction for an offence committed within 
a set follow-up period and disposed of within either the follow-up period or 
waiting period. 
 
Cohort definition used in the Proven Re-offending Statistics Quarterly 
Bulletin – the proven re-offending cohort consists of all offenders 
discharged from custody, otherwise sanctioned at court, receiving a caution, 
reprimand or warning or tested positive for opiates or cocaine in each year. 
This cohort’s criminal history is collated and criminal behaviour is tracked 
over the following one year. Any offence committed in this one year period 
which is proven by a court conviction or out-of-court disposal (either in the 
one year period, or in a further six months waiting period) counts as a 
proven re-offence. The latest available publication is the Proven Re-
offending Statistics Quarterly Bulletin in England and Wales; Ministry of 
Justice, October 2012. 
 
39

 
www.justice.gov.uk/statistics/reoffending/proven-re-offending 
Cohort definition used in the Local Adult Re-offending Quarterly 
Bulletin – the local adult re-offending measure takes a snapshot of all 
offenders, aged 18 or over, who are under probation supervision at the end 
of a quarter, and combines four such snapshots together. This cohort’s 
criminal history is collated and criminal behaviour is tracked over the 
following three months. Any offence committed in this three month period 
which is proven by a court conviction or out-of-court disposal (either in the 
three month period, or in a further three months waiting period) counts as a 
proven re-offence. The latest available publication is the Local Adult Re-
offending: 1 April 2011 – 31 March 2012, England and Wales; Ministry of 
Justice, August 2012. 
 
www.justice.gov.uk/statistics/reoffending/local-adult-reoffending 
 
Disposal (sentence type) 
 
Fine – a financial penalty imposed following conviction. 
 
Court orders – court orders include community sentences, community 
orders and suspended sentence orders supervised by the Probation 
Service. They do not include any pre or post release supervision. 
 
Criminal Justice Act 2003 (CJA03) – for offences committed on or after 4 
April 2005, the new community order replaced all existing community 
sentences for adults. The Act also introduced a new suspended sentence 
order for offences which pass the custody threshold. It also changed the 
release arrangements for prisoners. See Appendix A of Offender 
Management Caseload Statistics 2009 for more information. 
 
Community order – for offences committed on or after 4 April 2005, the 
new community order introduced under the CJA 2003 replaced all existing 
community sentences for those aged 18 years and over. This term refers to 
all court orders except suspended sentence orders and deferred sentences 
which may have a custodial component to the sentence. The court must add 
at least one, but could potentially add all 12 requirements depending on the 
offences and the offender. The requirements are: 
 
 unpaid work (formerly community service/community punishment) – a 
requirement to complete between 40 and 300 hours’ unpaid work; 
 
 activity – for example, to attend basic skills classes; 
 
 programme – there are several designed to reduce the prospects of 
re-offending; 
 
 prohibited activity – a requirement not do so something that is likely 
to lead to further offence or nuisance; 
 
 curfew – which is electronically monitored; 
 
 
40

 
 exclusion – this is not used frequently as there is no reliable 
electronic monitoring yet available; 
 
 residence – requirement to reside only where approved by probation 
officer; 
 
 mental health treatment (requires offender’s consent); 
 
 drug rehabilitation (requires offender’s consent); 
 
 alcohol treatment (requires offender’s consent); 
 
 supervision – meetings with probation officer to address 
needs/offending behaviour; and 
 
 attendance centre – between a minimum of 12 hours and a maximum 
of 36 in total which includes three hours of activity. 
 
Typically, the more serious the offence and the more extensive the 
offender’s needs, the more requirements there will be. Most orders will 
comprise of one or two requirements, but there are packages of several 
requirements available where required. The court tailors the order as 
appropriate and is guided by the Probation Service through a pre-sentence 
report. 
 
Suspended sentence order (SSO) – the CJA 2003 introduced a new 
suspended sentence order which is made up of the same requirements as a 
community order and, in the absence of breach is served wholly in the 
community supervised by the Probation Service. It consists of an 
‘operational period’ (the time for which the custodial sentence is suspended) 
and a ‘supervision period’ (the time during which any requirements take 
effect). Both may be between six months and two years and the ‘supervision 
period’ cannot be longer than the ‘operational period’, although it may be 
shorter. Failure to comply with the requirements of the order or commission 
of another offence will almost certainly result in a custodial sentence. 
 
Pre CJA03 Court Orders – Community sentences 
 
Community punishment order (CPO) – the offender is required to 
undertake unpaid community work. 
 
Community rehabilitation order (CRO) - a community sentence which 
may have additional requirements such as residence, probation centre 
attendance or treatment for drug, alcohol or mental health problems. 
 
Community punishment and rehabilitation order (CPRO) – a community 
sentence consisting of probation supervision alongside community 
punishment, with additional conditions like those of a community 
rehabilitation order. 
 
 
41

 
Drug treatment and testing order (DTTO) – a community sentence 
targeted at offenders with drug-misuse problems. 
 
Custody – the offender is awarded a sentence to be served in prison or a 
Young Offenders Institute (YOI). If the offender is given a sentence of 12 
months or over, or is aged under 22 on release, the offender is supervised 
by the Probation Service on release. It is important to note that the sentence 
lengths and youth disposals awarded will be longer than the time served in 
custody. For more information please refer to Appendix A of Offender 
Management Caseload Statistics 2009. 
 
Short sentences (under 12 months) – those sentenced to under 12 
months (made under the Criminal Justice Act 1991) spend the first half of 
their sentence in prison and are then released and considered ‘at risk’ for 
the remaining period. This means they are under no positive obligations and 
do not report to the Probation Service, but if they commit a further 
imprisonable offence during the ‘at risk’ period, they can be made to serve 
the remainder of the sentence in addition to the punishment for the new 
offence. The exception to this is those aged 18 to 20 who have a minimum 
of three month’s supervision on release. 
 
Sentences of 12 months or over – the CJA03 created a distinction 
between standard determinate sentences and public protection sentences. 
Offenders sentenced to a standard determinate sentence serve the first half 
in prison and the second half in the community on licence. 
 
Youth disposal (sentence type) 
 
Reprimand or warning – a reprimand is a formal verbal warning given by a 
police officer to a juvenile offender who admits they are guilty for a minor 
first offence. A final warning is similar to a reprimand, but can be used for 
either the first or second offence, and includes an assessment of the 
juvenile to determine the causes of their offending behaviour and a 
programme of activities is designed to address them. 
 
First-tier penalties 
 
Discharge – a juvenile offender is given an absolute discharge when they 
admit guilt, or are found guilty, with no further action taken. An offender 
given a conditional discharge also receives no immediate punishment, but is 
given a set period during which, if they commit a further offence, they can 
be brought back to court and re-sentenced. 
 
 Fine – the size of the fine depends on the offence committed and the 
offender’s financial circumstances. In the case of juveniles under 16, 
the fine is the responsibility of the offender’s parent or carer. 
 Referral order – this is given to juveniles pleading guilty and for 
whom it is their first time at court (unless the offence is so serious it 
merits a custodial sentence or it is of a relatively minor nature). The 
offender is required to attend a Youth Offender Panel to agree a 
 
42

 
contract, aimed to repair the harm caused by the offence and 
address the causes of the offending behaviour. 
 Reparation order – the offender is required to repair the harm 
caused by their offence either directly to the victim or indirectly to the 
community. 
 
Youth Rehabilitation Order – a community sentence for juvenile offenders, 
which came into effect on 30 November 2009 as part of the Criminal Justice 
and Immigration Act 2008. It combines a number of sentences into one 
generic sentence and is the standard community sentence used for the 
majority of children and young people who offend. The following 
requirements can be attached to a Youth Rehabilitation Order (YRO): 
 
 activity requirement 
 
 curfew requirement 
 
 exclusion requirement 
 
 local authority residence requirement 
 
 education requirement 
 
 mental health treatment requirement 
 
 unpaid work requirement 
 
 drug testing requirement 
 
 intoxicating substance misuse requirement 
 
 supervision requirement 
 
 electronic monitoring requirement 
 
 prohibited activity requirement 
 
 drug treatment requirement 
 
 residence requirement 
 
 programme requirement 
 
 attendance centre requirement 
 
 intensive supervision and surveillance 
 
 intensive fostering 
 
 
43

 
The following community sentences are replaced by the YRO, but will 
continue to exist for those that committed an offence before 30 November 
2009. The YRO is only available for those that committed an offence on or 
after the 30 November 2009. 
 
 action plan order 
 
 curfew order 
 
 supervision order 
 
 supervision order and conditions 
 
 community punishment order 
 
 community punishment and rehabilitation order 
 
 attendance centre order 
 
 drug treatment and testing order 
 
 exclusion order 
 
 community rehabilitation order 
 
Prison categories 
 
Category B and category C prisons hold sentenced prisoners of their 
respective categories, including life sentenced prisoners. The regime 
focuses on programmes that address offending behaviour and provide 
education, vocational training and purposeful work for prisoners who will 
normally spend several years in one prison. 
 
High security prisons hold category A and B prisoners. Category A 
prisoners are managed by a process of dispersal, and these prisons also 
hold a proportion of category B prisoners for whom they provide a similar 
regime to a category B prison. The category B prisoners held in a High 
Security Prison are not necessarily any more dangerous or difficult to 
manage than those in category B prisons. 
 
Female prisons, as the name implies, hold female prisoners. Because of 
the smaller numbers, they are not divided into the same number of 
categories although there are variations in security levels. 
 
Local prisons serve the courts in the area. Historically their main function 
was to hold un-convicted and un-sentenced prisoners and, once a prisoner 
had been sentenced, to allocate them on to a category B, C or D prison as 
appropriate to serve their sentence. However, pressure on places means 
that many shorter term prisoners serve their entire sentence in a local 
prison, while longer term prisoners also complete some offending behaviour 
 
44

 
and training programmes there before moving on to lower security 
conditions. All local prisons operate to category B security standards. 
 
Open prisons have much lower levels of physical security and only hold 
category D prisoners. Many prisoners in open prisons will be allowed to go 
out of the prison on a daily basis to take part in voluntary or paid work in the 
community in preparation for their approaching release. 
 
Miscellaneous terms 
 
Drug-misusing offenders 
 
There are four ways a drug-misusing offender can be identified: 
 
 Individuals who have tested positive for heroin or crack/cocaine 
following an arrest or charge for ‘trigger’ offences (largely acquisitive 
crime offences) as part of the Drug Interventions Programme (DIP) 
are included as adult proven offenders. 
 
 Any offender that received an OASys assessment whilst on licence 
or on a community sentence and are either recorded as being subject 
to a current Drug Treatment and Testing Order (DTTO) or Drug 
Rehabilitation Requirement (DRR), or are assessed as having a 
criminogenic drug need. 
 
 Any offender identified as requiring further drug interventions by 
Counselling, Assessment, Referral, Advice, Throughcare (CARAT) 
teams in prison, and now being released into the community. 
 
 Any offender identified by local Criminal Justice Integrated Teams 
(CJITs) as requiring further intervention for their drug use and 
offending as part of DIP. 
 
National Probation Service – the National Probation Service generally 
deals with those aged 18 years and over. (Those under 18 are mostly dealt 
with by Youth Offending Teams, answering to the Youth Justice Board.) 
They are responsible for supervising offenders who are given community 
sentences and suspended sentence orders by the courts, as well as 
offenders given custodial sentences, both pre and post their release. 
 
Police National Computer – the Police National Computer (PNC) is the 
police's administrative IT system used by all police forces in England and 
Wales and managed by the National Policing Improvement Agency. As with 
any large scale recording system the PNC is subject to possible errors with 
data entry and processing. The MoJ maintains a database based on weekly 
extracts of selected data from the PNC in order to compile statistics and 
conduct research on re-offending and criminal histories. The PNC largely 
covers recordable offences – these are all indictable and triable-either-way 
offences plus many of the more serious summary offences. All figures 
derived from the MoJ's PNC database, and in particular those for the most 
recent months, are likely to be revised as more information is recorded by 
the police. 
 
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Prolific and other priority offenders – the Prolific and other Priority 
Offenders Programme (PPO) aims to use a multi-agency approach to focus 
on a very small, but hard core group of prolific/persistent offenders who 
commit disproportionate amounts of crime and cause disproportionate harm 
to their local communities. The identification of a PPO is undertaken at a 
local level involving police, local authorities, prison and probation services 
and youth offending teams. The factors that influence the decision of 
whether an offender is included in the PPO programme are: 
 
 the nature and volume of crimes they commit; 
 
 the nature and volume of other harm they cause; and 
 
 the detrimental impact they have on their community. 
 
Recordable offences – recordable offences are those that the police are 
required to record on the PNC. They include all offences for which a 
custodial sentence can be given plus a range of other offences defined as 
recordable in legislation. They exclude a range of less serious summary 
offences, for example television licence evasion, driving without insurance, 
speeding and vehicle tax offences. 
 
Indictable and summary offences – summary offences are triable only by 
a magistrates’ court. This group includes motoring offences, common 
assault and criminal damage up to £5,000. More serious offences are 
classed either as triable-either-way (these can be tried either at the Crown 
Court or at a magistrates’ court and include criminal damage where the 
value is £5,000 or greater, theft and burglary) or indictable-only (the most 
serious offences that must be tried at the Crown Court; these ‘indictable-
only’ offences include murder, manslaughter, rape and robbery). The term 
indictable offences is used to refer to all triable-either-way and ‘indictable-
only’ offences. 
 
Offence group – a split of offences into 21 separate groups. A more 
detailed split of the 10 indictable offence groups (violence against the 
person, sexual offences, burglary, robbery, theft and handling and stolen 
goods, fraud and forgery, criminal damage, drug offences, other indictable 
offences (excluding motoring), indictable motoring) and the two summary 
offence groups (summary non-motoring and summary motoring offence 
types).
 
46

 
Appendix C: Comparison of the three measures 
of re-offending 
 
Figure A1 below compares how the three measures of re-offending (the 
headline proven re-offending measure, the early estimates of re-offending 
and local adult re-offending) are constructed. It shows the period over which 
the re-offending cohort is formed, the time over which re-offending is 
measured, the additional time allowed for re-offending to be proven, and the 
time taken to collect and analyse the data, and then to publish. 
 
Figure A1: how the three re-offending measures are constructed 
 
Jan-Mar
Apr-Jun
Jul-Sep
Oct-Dec
Jan-Mar
Apr-Jun
Jul-Sep
Oct-Dec
Jan-Mar
Apr-Jun
Jul-Sep
Oct-Dec
2009 Headline
Cohort formation 
measure
Re-offences
Re-offences proven
Data collection and analysis
Publication
Oct-11
2010 Early Estimates
Cohort formation 
measure
Re-offences
Re-offences proven
Data collection and analysis
Publication
Oct-11
Snapshot 1
Snapshot 2
Snapshot 3
Snapshot 4
Local Re-offending 
Cohort formation based on probation caseload 
snapshots at end of each quarter 
measure
Re-offences
Re-offences proven
Data collection and analysis
Publication
Nov-11
2009
2010
2011
 
 
Cohort formation 
Headline measure and early estimates: offenders enter the cohort when 
they receive a caution (adults), a final warning or reprimand (juveniles), are 
given a non-custodial conviction, are released from custody or test positive 
for cocaine or opiates in the cohort formation period shown. 
 
Local adult re-offending: this uses a snapshot of all offenders aged 18 or 
over, who are under probation supervision at the end of a quarter, and 
combines four such  snapshots together. 
 
Re-offences 
Headline measure: A re-offence is counted if the offence occurs within the 
"Re-offences" period shown. This is within 12 months of entering the cohort. 
 
Early estimates and local adult re-offending: A re-offence is counted if the 
offence occurs within three months of entering the cohort for the early 
estimates measure and within three months following each of the four 
caseload snapshots for the local re-offending measure. 
 
Re-offences proven 
Headline measure: For a re-offence to be counted it must also be proven 
within the "Re-offences proven" period shown. This is within six months of 
the re-offence. 
 
Early estimates and local adult re-offending: For a re-offence to be counted 
it must also be proven within the "Re-offences proven" period shown. This is 
within three months of the re-offence. 
 
 
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48
Contact details and further information 
 
For queries, comments or further information, please contact: 
 
Nick Mavron 
Justice Statistics Analytical Services 
Ministry of Justice 
7th floor 
102 Petty France 
London 
SW1H 9AJ 
 
Email: xxx@xxx.xx 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
© Crown copyright 
Produced by the Ministry of Justice 
Alternative formats are available on request from 
xxx@xxx.xx