SSA (Static, Stable and Acute)

Addiction rehabilitation foundation GGZ

The Static/Stable/Acute (SSA) is a combination of static and dynamic instruments to estimate the risk of future sexual and violent offending behaviour in perpetrators of sexual offences. The combination is used by the probation service, among other things, to determine the intensity of supervision and counselling upon return to society and to evaluate progress in the trajectory.

Last change on 15th of December 2025, at 9:19 (CET) | Publication Standard 1.0

• Publication category: Impactful algorithms
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• Status: In use

General information

Theme

Law

Begin date

2018-04

Contact information

[e-mail]

Responsible use

Goal and impact

In order to assess the risk of future sexual and violent offence behaviour in perpetrators of sexual offences, the Static 99r/Stable 2007/Acute 2007 (SSA) is used in the probation service. The use of this tool is deployed only by probation workers who are trained for this purpose and have completed the training with a certificate. The SSA combination can be used to determine whether, and if so which, interventions the probation service considers necessary to influence, manage, and contribute to the client's resocialisation risk. In addition, the SSA combination is of value in determining goals and intensity of supervision and counselling of the client and evaluating progress during the probation programme. The instruments are therefore used both in the counselling phase and during supervision. The three tools were originally Canadian and translated into Dutch in 2014.

The probation organisations in the Netherlands all use the SSA. These include the institutions of Stichting Verslavingsreclassering GGZ, Reclassering Nederland and Stichting Leger des Heils Jeugdbescherming & Reclassering.

Considerations

Research shows that an estimate based on the results of a scientific instrument combined with the professional's estimate is better than one based solely on the professional's experience. The calculation model behind the recidivism figures is based on scientific research into factors influencing recidivism. The outcome of the SSA is not leading in the final risk assessment, the advice given and the actions of the probation worker. The model supports professional judgement.

STATIC-99R

Estimating the recidivism risk of sex offenders is of great social importance. A good assessment prevents new victims. The STATIC-99R can be used to estimate the recidivism risk of a person who has committed a sexual offence. The STATIC-99R has a broad scientific basis internationally and, together with the STABLE-2007 and the ACUTE-2007, is widely used within the justice chain.

STABLE-2007

Counselling and treating perpetrators of sexual offences involves major challenges. The STABLE-2007 provides tools for drawing up a counselling plan. The instrument measures dynamic risk factors in perpetrators of sexual offences. These are factors that can change over time and can be worked on together with the client to achieve behavioural change and thus control potential risks. They are the factors that give input to the supervision plan, for example. Treating dynamic risk factors effectively reduces the risk of recidivism and thus increases social safety.

ACUTE-2007

Supervising people who have committed sexual offences is of great importance in preventing recidivism. This is a task that can be imposed on the probation service by the court. An important question during supervision is when supervision should be more or less intensive. The ACUTE-2007 helps determine this intensity.

Human intervention

When using the SSA, there is always meaningful human intervention. Thus, the professional always makes the final decision on the risk assessment and the most appropriate advice and interventions for the client. It is not just about the outcome of the SSA, the probation officer also answers questions in all other areas of life that could potentially be protective or risk-increasing and ultimately - all things considered - arrives at a balanced assessment of the risk of recidivism.

Only staff trained in and certified to use the SSA may work with the combination of instruments. When using the instruments, the instrument manual should always be used. Employees themselves interpret and substantiate the risk of recidivism based on a total score that emerges from the instruments using table books that belong to the instrument.

During training, attention is also paid to interpreting results, reporting as well as the fact that a risk assessment is an estimate in which one compares characteristics of an individual against a group average of a group of persons with similar characteristics.

The professional always makes the final decision on the individual risk assessment and the most appropriate advice for the client and does not automatically follow the score according to the instrument. This includes consultation with colleagues (four-eye principle). The choice is substantiated whereby the various considerations are discussed and described (including the risk assessment model used as well as any other relevant information that came to light in the study).

Risk management

Only trained and certified staff should use and apply the instruments and associated materials. When applying the instruments, the manuals obtained after completing the training should be used. SSA training is provided in the Netherlands by platform sexology. More information about the training can be found in their flyer (via https://dfzs.nl/files/pfs-flyer-04-2024.pdf). This training is part of a more extensive curriculum that starts with training in working with perpetrators of sexual offences.

There are contraindications to using the tools. For example, the SSA were developed for use with adult male offenders (18 years or older) who have been charged or convicted of at least one sexually (or sexually motivated) offence against a child or non-consenting adult. To minimise the risk of the tools being applied to individuals for whom it is not intended, only certified staff are allowed to apply the tools and the multi-weight principle is applied.

The results of the SSA are shown in the appendix of the advisory report that goes to the client (the suspect or convict), the prosecutor and judge. In this way, it is clear and transparent to everyone which instruments the probation service has worked with and on which the probation service's advice is based. To prevent other people from misinterpreting the results, the report contains the description of how the advice was produced, a clear rationale for the advice and also how the outcome of instruments such as the SSA was taken into account in it.

Through knowledge circles and contact with the Platform Forensic Sexology, developments around the instrument are monitored and any updates are made.

Legal basis

The basis for the probation service's use of risk assessment instruments lies in their legal duties. The legal tasks of advice and supervision are relevant here and are laid down in various articles in the Penal Code and the Code of Criminal Procedure, among others. A list of the relevant legal articles for each task is given below. A link to the main articles is included under reference legal basis.

Opinion:

The basis for processing the personal data of clients (suspects and convicted persons) for the purpose of the counselling task lies in a legal obligation (Article 6(1)(c) AVG) and/or the performance of a public law task (Article 6(1)(e) AVG) in conjunction with, among others, the following articles

Reclasseringsregeling 1995: articles 8 paragraph 1 sub a, 9 and 10;

Code of Criminal Procedure: articles 63 paragraph 6, 147, 177 paragraph 2, 310, 6:2:12 paragraph 2, 6:6:23a paragraph 3, 6:6:23c paragraph 3;

Penal Code: articles 38m paragraph 4, 38z paragraph 2;

Transfer of Enforcement of Criminal Judgements Act: section 19(1);

Penitentiary Institutions Act: article 18a

Penitentiary Measure, article 7 paragraph 2

Decree on Forensic Care: article 6.2a subsection 2 sub d (advice design supervision under article 43 subsection 4 Pbw)

Supervision:

The basis for processing the personal data of clients (suspects and convicts) for the purpose of supervision and counselling by the probation service lies in a legal obligation (Article 6 paragraph 1 sub c AVG) and/or the performance of a public law task (Article 6 paragraph 1 sub e AVG) in connection with

Reclasseringsregeling 1995: articles 8 paragraph 1 sub b, 11 and 12;

Penal Code: articles 14c paragraph 3 under b jo paragraph 6, 38 paragraph 2, 77z paragraph 3 under b, 77aa paragraph 3;

Code of Criminal Procedure: articles 80, 167 paragraph 2, 6:2:11 paragraph 2 sub b, 6:3:12 paragraph 3, 6:3:14, 6:6:10, 6:6:19 and 6:6:23b

Pardons Act: article 15 paragraph 1;

Penitentiary Institutions Act: articles 4 and 43 paragraph 4;

Penitentiary measure: articles 8 and 9;

Beginswet verpleging ter beschikking gestelden: article 51 paragraph 2;

Regulations for treatment of persons placed at risk: articles 59 to 61, 68 to 70;

Decree on forensic care: article 2.7;

Decree on enforcement of criminal decisions: articles 3:1 to 3:5.

Below is a reference to some of the most important articles of law:

Links to legal bases

• Probation Regulation 1995: https://wetten.overheid.nl/BWBR0007120/2019-06-26#Hoofdstuk3
• Art. 147 WvSv: https://wetten.overheid.nl/BWBR0001903/2025-07-01#BoekTweede
• Article 6:2:12 WvSv: https://wetten.overheid.nl/jci1.3:c:BWBR0001903&boek=6&hoofdstuk=2&titeldeel=Tweede&artikel=6:2:12&z=2025-07-01&g=2025-07-01
• Article 14c WvSr: https://wetten.overheid.nl/jci1.3:c:BWBR0001854&boek=Eerste&titeldeel=II&artikel=14c&z=2025-07-01&g=2025-07-01

Elaboration on impact assessments

DPIA (Data Protection Impact Assessment ) is carried out.

Operations

Data

The Static-99R contains 10 relatively easy-to-score mostly static variables, covering age, previously committed (sexual) offences, previous convictions, victim characteristics and whether a person has ever lived together.

The Stable contains 12 dynamic variables related to social contacts and social interactions, impulsive behaviour, problem-solving ability, involvement with or identification with others and questions focused on sexual behaviour.

The Acute consists of 7 questions related to social support, substance abuse, emotional state and sexual preoccupation.

Technical design

The SSA are built into the probation service's digital work environment. In it, questions are answered and total scores are calculated. Estimates regarding recidivism risk are made by the professional himself using this total score and the corresponding table books. Outcomes are recorded with substantiation.

The Static-99R contains 10 relatively easy-to-score predominantly static variables. The total score is the sum of the items and the total scores are divided into the nominal risk categories low, low-moderate, moderate-high and high. That total score can be compared to the appropriate norm group by the employee in a table and, based on that, the corresponding recidivism risk is displayed.

The Stable-2007 contains 12 dynamic variables (plus 1 additional item for offenders with victims under 14). These can be answered through, among other things, interviews with the client himself. In the Stable-2007 manual, staff can find information on the background of the questions. It also contains sample interview questions. The total score displayed is the sum of the items and the total scores are divided into the risk categories low, moderate and high. Based on this score, the supervision focus can be determined and the supervision plan can be evaluated. The instrument is used in conjunction with the STATIC-99R.

The Acute-2007 contains 7 acutely dynamic variables. The tool helps to set priorities in the (very) near future. The scoring manual includes examples of behavioural observations and questions that can be raised during contact with the offender. The scores on the items are added up and give an indication of the intensity of supervision needed at that time. The instrument is used in conjunction with the STATIC-99R and the STABLE-2007.

External provider

The three tools were originally Canadian and translated into Dutch in 2014. Platform for Forensic Sexology is the supplier: https://platformforensischeseksuologie.nl/