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The Dutch Recidivism Monitor (WODC 2004)

Bouke Wartna, Martine Blom, Nikolaj Tollenaar et Stefan Bogaerts
Cet article est une traduction de :
L’observatoire de la récidive aux Pays-Bas (2004)

Texte intégral

The WODC Recidivism Monitor

  • 1   This is a translation of a leaflet available on the site of the WODC ( The original (...)

1The WODC Recidivism Monitor1 is a long-term research project that conducts standardised measurements of recidivism amongst diverse groups of offenders. This project will enable the Ministry of Justice in the Netherlands to obtain a clearer overview as to the outcomes of penal interventions and the course of criminal careers amongst both young and adult offenders. Measurements carried out as part of the Recidivism Monitor are carried out in the same manner throughout. Consequently, the results of the research are mutually comparable. Certain measurements are repeated at fixed intervals, in order to follow the subsequent course of the criminal career of the most important groups of offenders.

The Dutch Offenders Index

  • 2   Dutch title: ‘Onderzoek- en Beleidsdatabase Justitiële Documentatie’ – OBJD.

2The data for the research are taken from the Dutch Offenders Index (DOI)2, a database that has been developed especially with the Recidivism Monitor in mind. The DOI is an encrypted, anonymised copy of the JDS, the official judicial documentation system that is managed by the Central Judicial Documentation centre (CJD).

3The JDS provides an overview of all physical persons or legal entities that have come into contact with the judicial system in the Netherlands as a suspect of a criminal offence.  For each criminal case, it is recorded when a case is registered, and at what court, along with details of the crimes to which it related and how and by which authority the case was dealt with.

4Every three months, the DOI is refreshed with the most recent data from the JDS. An important difference between the DOI and the JDS is that the data in the DOI is never eliminated even though a case may be past the statute of limitations; all data remain available for research purposes. A pre-condition for inclusion in the JDS is that the person or entity came into contact with the judicial system after 1996. If that is not the case, it may be the case that any cases relating to a suspect may not yet have been entered into the system and cannot therefore be found in the DOI.

Central Judicial Documentation centre (CJD)

The Judicial Documentation System (JDS) contains documentation relating to almost 2.5 million people and almost 8 million criminal cases. The database began at the beginning of the 1990s. Until that time, all information about prosecuted cases and their conclusion were recorded by the district courts using a card-based system. The cards were then sent to the CJD, where the details of non-precluded or non-lapsed cases were photographically recorded and captured as images. Whenever a new report about a person is received, a search is first of all carried out in order to ascertain whether any cases are recorded in the image files. If that is the case, these old cases are entered into the JDS.

Nowadays, new criminal cases are added directly to the JDS from COMPAS, which is the administration system used in courts. Automatic data forwarding was not introduced simultaneously at all locations however. The last district in which it was introduced was not connected to JDS until 1996. This means that the JDS (and therefore also the DOI) is only complete for those people who (again) came into contact with the authorities after 1996, and any research must take account of this. Anyone who has not had any further contact with the judicial authorities since 1996 may still have old cases in the image files. These cases must first of all be fed in and only after the next time the DOI is refreshed will be image of their criminal career be complete.

Research into specific interventions or groups of offenders

5The DOI contains only the basic details of the outcome of each case. The type of punishment or measure is recorded, along with the extent or duration thereof. In any research as to interventions that do not appear in the DOI, the data of those offenders cannot be drawn directly from the database and it is therefore necessary to introduce an intermediary stage that involves the CJD. Upon request, the CJD will supply the encrypted numbers under which the relevant persons can be found in the DOI. In order to do this, the following information must be available in respect of each person that forms part of the study group:

  • Respondent number, if available the standard number

  • Personal details: surname, infixes and full forenames

  • Date of birth, place and country of birth

  • Reference number of court of first instance (including district code)

  • Start and end-date of punishment or penalty

6Using the personal data, the CJD will search for the relevant encrypted numbers. Once these are known, all relevant information relating to the case, the crime and the outcome can be extracted from the DOI. As this procedure infringes upon the anonymity of the respondent, the permission of the Minister of Justice is required for research of this type. All applications for information from the DOI are handled by the Research and Documentation Centre of the Netherlands Ministry of Justice (WODC).

Processing of raw research data

The data are not directly suitable for analysis, but first of all need to be processed. This is carried out by means of several stages:

  • Allocation of the raw data under fixed headings

  • Summarisation of the details of the crime

  • Processing the details of the outcome

  • Determining the time at which the cases took place

Re 1) Most of the fields in the DOI consist of text items. In order to enable the information to be divided up in a purposeful manner, these strings must first of all be converted into values in the form of digital variables. A number of programs have been developed for this purpose.

Re 2) The details of the crimes committed are recorded in the DOI in the form of the laws that have been contravened. Each punishable offence consists of a maximum of five items of law. The number of facts per case is unlimited. The first stage in processing the details of the crimes is recognising the potential punishment that is available for each act. This is the maximum sentence that can be imposed for a certain type of criminal act. If more than one legal article is named in relation to a certain criminal act, the article that is allocated is the one that carries the maximum penalty. In cases involving a “punishable attempt to provoke or commit a criminal act” or “punishable preparation of a crime” or “complicity”, the maximum penalty is corrected in accordance with the Dutch Criminal Code.

In addition to the maximum penalty, each criminal act or combination of articles is also allocated a “cbs code”. This is the code used by National Bureau of Statistics in order to classify crimes. Based on this code, the punishable acts can be divided in different ways. Once a criminal act has been allocated a maximum sentence and a crime code, the five criminal acts per case with the highest maximum penalty are selected. In each case, various types of crimes may arise, one of which is the one that carries the highest maximum penalty.

Re 3) Criminal cases may be settled in a variety of different ways. A case may incorporate more than one penalty component and there is no maximum number as to the number of sentences that can be recorded. The details of the outcome of a case are also summarised. This is carried out in two ways: In the first instance, each case is examined in order to establish the type of outcome. Then, the outcome of each case is subdivided into one of the following categories: custodial measures, unconditional imprisonment, community service orders, suspended prison sentences, fines, fixed penalties and discretionary dismissals. By adopting this approach, we keep sight of the occurrence of combinations of different sentence components, but we are also aware of the highest penalty that has been handed down in a particular case. Alongside the type of outcome, the extent or duration of the penalty is also recorded.

Re 4) Once the details of the crime and the outcome have been summarised, the sequence of the criminal cases is determined on a person-by-person basis. This is carried out by means of the year of registration of the criminal case. The DOI does of course include data regarding the occurrence of crimes and the decisions taken in each case, but these do not constitute a good alternative.  Data relating to the occurrence of crimes are only available for crimes registered after 1996 and decision data are too heavily influenced by the time taken for a case to pass through the court system. Using the year of registration also has its disadvantages, however. If a person commits more than one criminal act during the course of one particular year, this information is not specific enough. In order to determine more accurately the time at which a crime took place, the month of registration will in due course be incorporated in the JDS.  Until then, we make an estimate as to the month of registration. In cases where the possible date upon which a crime was committed and the date upon which a decision was made fall within the same year, a random month of registration situated between these two dates is selected. This estimated date forms the basis for further analysis.

Operational definition of recidivism

7The decision to use the DOI as the main source of data for the research implies that for the purposes of the Recidivism Monitor, only those crimes are charted that are handled by the Public Prosecution Service. No statements are made as to crimes that are not detected and prosecuted. We also do not take into account crimes that are dealt with in the sub-district courts. This section of recorded criminal acts, known as “minor offences”, consists – for approximately 90% - of traffic offences, 60% of which are speed-related. Of all cases involving criminal acts, we do not include those cases that ended in an acquittal, a dismissal by reason of unlikelihood of conviction, or another such outcome.  In contrast, cases that are resolved by the Public Prosecution Service (Openbaar Ministerie) in the form of a fixed penalty or a discretionary dismissal are included. In the Netherlands well over half of the criminal cases involving serious crimes are dealt with by Public Prosecutor.

Criteria for recidivism

8Five fixed criteria are used in order to determine recidivism, a description of which can be found in Table 1. The first three criteria – general, serious and very serious recidivism – differ from one another solely in relation to the seriousness of the crimes brought to court. They always have the same meaning, i.e. in each study group. This does not apply in the case of special or specific recidivism. The meaning of these criteria depends upon the nature of the case for which a person has been included in the relevant study group. In the case of traffic offenders, for example, special recidivism is taken to mean a further involvement with the judicial authorities as the result of a traffic offence. In the case of sex offenders, special recidivism is deemed to have occurred when they are once again prosecuted for a sex offence.

Recidivism criteria, as used by the WODC Recidivism Monitor



General recidivism

All further involvement with the judicial authorities, irrespective of the nature and seriousness of the crimes committed. This does not include crimes that result in acquittal, a dismissal by reason of unlikelihood of conviction or another such outcome.

Serious recidivism

Renewed, valid involvement with the judicial authorities in relation to a crime with a maximum sentence of 4 years or more.

Very serious recidivism

Renewed, valid involvement with the judicial authorities in relation to a crime with a maximum sentence of 8 years or more.

Special recidivism

Renewed, valid involvement with the judicial authorities, based upon the same type of crime as the one in the original case.

Specific recidivism

Renewed, valid involvement with the judicial authorities, based upon a contravention of the same statutory article as in the original case.

9* Crimes with a lower maximum penalty, but for which the perpetrator may be held on remand, also fall within this category

What types of analysis are carried out?

10Based upon the above criteria, the recidivism of the offenders in any study group can be computed. We make a distinction between the following aspects of recidivism:

  • The prevalence of recidivism: this relates to the question as to which part of the (sub)group has reoffended.

  • The speed within which an individual reoffended: this is determined by the time at which the subsequent involvement with the judicial authorities occurred.

  • The frequency of recidivism: this relates to the number of new involvements with the judicial authorities that a reoffender has accumulated since the original case.

  • The nature and seriousness of the crimes committed by the reoffender.

  • The volume of recidivism: this relates to the magnitude and seriousness of all new offences committed by the members of a study group.

11The prevalence and the speed of recidivism are determined on the basis of a survival analysis. This is a technique that takes account of the differences in the time period during which it was possible to monitor the individuals that form part of the research. For each of the criteria, the percentage of the study group that was subsequently involved with the judicial authorities is calculated. This is not carried out over a fixed period (like in: ‘after 2 years, the percentage of general recidivism is 50%’), but for each period for which observations are available.  For each subsequent year following the original case, a figure is established relating to the section of the study group that has already reoffended (graph 1).

Graph 1: The prevalence of general recidivism amongst two groups of offenders (See appendix).

  • 3   Cases that have not yet been settled are not included in this analysis. Cases resulting in the jo (...)

12The frequency of recidivism is calculated for the reoffenders in a group, and is expressed in terms of the average number of new involvements with the judicial authorities that they have accumulated since the original case. For each year, the number of involvements due to reoffending is divided by the number of people who have reoffended up to that point in time.  The nature of the recidivism is described on the basis of the types of crimes that have been committed. For each group, a table is compiled with the percentages of the types of crimes that have occurred. The seriousness of the involvements with the judicial authorities due to recidivism is charted by investigating the the penalties imposed in these new criminal cases.3 Finally, the volume of recidivism is illustrated as in Graph 2. The lines on the graph show how many involvements with the judicial authorities were accumulated by the entire group during the course of a number of years, as a result of relatively minor, serious, or very serious crimes. In order to enable comparisons to be drawn with the outcomes of other research, the numbers are always calculated across a group consisting of 100 individuals.

Graph 2: The number of new involvements with the judicial authorities, according to the seriousness of the crimes committed (see appendix).

Additional analyses

The percentage of reoffenders, the average number of new involvements with the judicial authorities, the type and the sentence imposed upon reoffenders form the descriptive statistics that create a picture as to the nature and scope of recidivism within a group. Wherever possible, an examination also takes place into the factors that influence an individual to continue his/her criminal career. Additional data is required in order to carry out analyses of this type: facts on the personal background of the respondents, diagnostic data and data as to the course of the relevant intervention or about the circumstances in which the party found him or herself, once the sentence had been carried out. If such data are available, they are then linked to the information from the DOI and we are able to study the links between the various quantities.

Research programme

13A large number of measurements of recidivism are scheduled to take place during the next few years. As part of the WODC Recividism Monitor, research will take place into the outflow results of penal interventions and the course of criminal careers. The research will focus upon the following groups of offenders, amongst others:

  • All persons who were prosecuted in 1997 and received a sanction (fixed penalty, fine, Community Service Order, term of imprisonment etc.)

  • Persons in custody who have left a prison or remand centre since 1996

  • Persons subject to a hospital order that ended after 1974

  • All young people who have been released from a youth detention or treatment centre since 1997

  • Persons prosecuted for a traffic offence in 1997

  • Offenders prosecuted in 1997 due to contravention of the Opium Act or the Abuse of Chemical Substances (Prevention) Act

  • Offenders who were prosecuted frequently during 1997-2001 (‘prolific offenders’)

  • Those that committed (serious) violent or sexual offences

  • Persons sentenced in 1994 for exhibitionism on at least one occasion

  • Participants of “Binnenste Buiten”, which is a reintegration-into-work scheme for young adult detainees

  • Participants of “nieuw Positief Initiatief”, a phased detention programme for long-term prisoners

  • Persons committing public nuisance offences who have taken part in group training sessions in social skills

  • Former clients of the Juvenile Rehabilitation Service, whose programme ended during the first quarter of 2000

14In total, hundreds of thousands of offenders are involved in the research. The measurements of the first four sub-projects are repeated on an annual basis so the further course of the criminal careers of these individuals can be charted. The involvement with the judicial authorities of the most persistent multiple offenders (adults and juveniles) is also monitored on a permanent basis.

The use of a predictive model

Based upon population data obtained from the DOI, the WODC has developed its own predictive model. In the case of all offenders prosecuted in 1997, research has been undertaken as to the influence of certain offender characteristics upon the likelihood of recidivism. Based upon the links that were established, it is now possible to produce a prognosis, for all categories of offenders, of the percentage of offenders that will have reoffended within 2 or 4 years. If we compare this predicted rate of recidivism with the actual rate that is observed within that group, it becomes clear whether the respondents have done better or worse than would have been expected by virtue of their background. If the actual rate of recidivism is lower than the predicted one, then this may be the result of the sanction that the offenders have undergone.

The WODC calculates the prognosis, based upon the following characteristics of the persons in the study:

  • Gender, current age and country of birth

  • Number of previous involvements with judicial authorities during their youth, i.e. before their 18th birthday

  • The number of involvements within the judicial authorities since the age of 18

  • The type of offence in the original case, compared to that of the current (outstanding) case

  • The year in which the first crime in the individual’s criminal career was recorded

  • The year in which the most recent (outstanding) case was recorded

It appears from the population study that these factors are the ones that display the closest link to the probability of recidivism. This is however a model that can only be used in the case of adult offenders. A separate model for recidivism amongst juvenile offenders is under development. The predictive model is useful in situations in which it is impossible to form a good control group. If these possibilities do exist, then it is preferable to make use of them. The predictive model consists of only a small number of (static) characteristics. It does not provide a perfect prediction of recidivism. It can never entirely be excluded that other factors may exist that will influence the extent of recidivism.

Supply of data on recidivism

15In order to guarantee the comparability of the outcomes of the research into outflow results of judicial interventions, it is important that the reoffender is always defined in the same manner. For the purposes of the Recividism Monitor, data are always taken from the same source, fixed criteria are used and the same statistics calculated as standard. Researchers from outside the WODC who are involved in evaluating penal interventions and who wish to access the recidivism data, may contact the WODC. Agreements will then be made as to the delivery of the DOI data, about any additional analyses required, and about the compiling of reports.

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Document annexe

  • Graphs (application/pdf – 945k)
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1   This is a translation of a leaflet available on the site of the WODC ( The original reference: De WODC-Recidivemonitor. B.S.J. Wartna, M. Blom, N. Tollenaar, Den Haag, WODC, 2004.

2   Dutch title: ‘Onderzoek- en Beleidsdatabase Justitiële Documentatie’ – OBJD.

3   Cases that have not yet been settled are not included in this analysis. Cases resulting in the joinder of cases are assigned the outcome of the case to which they were joined.

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Bouke Wartna, Martine Blom, Nikolaj Tollenaar et Stefan Bogaerts, « The Dutch Recidivism Monitor (WODC 2004) », Champ pénal/Penal field [En ligne], Vie de la recherche, mis en ligne le 26 novembre 2005, consulté le 22 janvier 2018. URL :

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Bouke Wartna

Project Manager +31 (0)70-3707604 Further information can be obtained from: Research and Documentation Centre (WODC).

Martine Blom

Nikolaj Tollenaar

Researcher +31 (0)70-3706564

Stefan Bogaerts

Head of CRSA research department

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