Sexual Violence Risk-20

The Sexual Violence Risk-20 (SVR-20) is a set of structured professional judgment guidelines for conducting sexual violence risk assessments in criminal and civil forensic contexts. The SVR-20 is not a quantitative test that yields norm-referenced or criterion-referenced scores. Rather, it was developed as an aide memoire to help systematize the risk assessment of individuals who (allegedly) have committed an act of sexual violence. More important, the concept of risk assessed by SVR-20 is not limited to likelihood of a new offense, as is commonly the case in actuarial (i.e., statistically based) tests. Other aspects of risk, such as level of victim harm, victim specificity, frequency, imminence, and likelihood are also addressable by this instrument.

SVR-20 Development

The SVR-20 comprises 20 items or factors considered to be minimally comprehensive in a sexual violence risk assessment. These items were gleaned from a systematic review of the scientific and professional literature in the area of sexual violence, sex offender recidivism, and sexual offender treatment. The guidelines for assessment and treatment of sexual offenders proposed by many different jurisdictions were also examined. The 20 factors selected for inclusion in the SVR-20 are divided into three domains: Psychosocial Adjustment, Sexual Offenses, and Future Plans.

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The Psychosocial Adjustment section comprises factors that are primarily historical in nature but also relate to current functioning. These factors include sexual deviation, victimization as a child, psychopathy, major mental illness, substance use problems, suicidal/homicidal ideation, relationship problems, employment problems, past nonsexual violent offenses, past nonviolent offenses, and past supervision failures. Clearly, some of these factors are more stable than others (e.g., past offenses), and some of these factors are more related to current functioning (e.g., substance use problems).

The Sexual Offenses section comprises items that are all related to the person’s historical and current sexual offenses. These factors include high-density sex offenses, multiple (types of) sex offenses, physical harm to victim(s) in sex offenses, use of weapons or threats of death in sex offenses, escalation in frequency or severity of sex offenses, extreme minimization or denial of sex offenses, and attitudes that support or condone sex offenses.

The Future Plans section comprises 2 items: lacks realistic plans and negative attitude toward intervention. The assessor may also include “other considerations” unique to the individual case that are considered to be important to the determination of risk.

SVR-20 Administration

Administration of the SVR-20 begins with a gathering of relevant information. The manual contains recommendations concerning what information to gather and how to gather it. Evaluators then rate the lifetime presence of the 20 standard risk factors as well as any case-specific risk factors identified. A brief definition of each risk factor is included in the manual. Next, evaluators rate recent change in the risk factors to identify whether there has been any increase or decrease over time in the risks associated with each. After rating the presence of individual risk factors, evaluators make an overall judgment of risk that is meant to reflect the level of intervention required to manage risk in the case. For example, people are judged to be “low risk” when evaluators believe they require minimal intervention (e.g., monitoring), “moderate risk” when evaluators believe they require enhanced intervention (e.g., a high-intensity sex offender treatment group, frequent reporting to a probation officer), and “high risk” when evaluators believe the person requires urgent or extreme intervention (e.g., incapacitation, supervised residence, emergency treatment).

SVR-20 Critique

Content Validity

The SVR-20 has been criticized because its items vary greatly in terms of the extent to which they are associated with the probability of recidivistic sexual violence, according to meta-analytic research. For example, factors such as high-density sexual offenses, sexual deviation, and attitudes supportive of offending are reasonably well established as predictors of recidivism in sexual offenders, whereas physical harm to victim(s), extreme minimization or denial, and negative attitude toward treatment are not. But the latter factors were included because they can be very important in helping professionals to assess aspects of risk other than likelihood (i.e., nature, severity, imminence, frequency) as well as to develop risk management strategies.

Interrater Reliability

Research indicates that judgments regarding the lifetime presence of risk factors and overall risk can be made with good interrater reliability. The interrater reliability of judgments regarding recent change has not been evaluated.

Predictive Validity

Research has provided good support for the use of the SVR-20 in sexual violence risk assessment. Individual studies and meta-analyses have demonstrated that the SVR-20 predicts sexually violent recidivism about as well as, and in some cases better than, commonly used actuarial tests. In studies that compared evaluators’ overall judgments of risk with simple linear combinations of risk factors, typically, overall judgments have better predictive validity.


In the authors’ experience, most assessors find that the inclusion of a locally normed actuarial risk assessment test alongside the SVR-20 allows for a more comprehensive appraisal of risk, and we support this practice. There is no convergence of opinion as to what is the best practice in this area; however, it is clear to most clinicians that the use of a single instrument is not necessarily the best manner in which to protect the public from future offending and that a more comprehensive and conservative approach is warranted.


  1. Boer, D. P. (2006). Sexual offender risk assessment strategies: Is there a convergence of opinion yet? Sexual Offender Treatment, 1, 1-4.
  2. Boer, D. P., Hart, S. D., Kropp, P. R., & Webster, C. D. (1997). Manual for the Sexual Violence Risk-20: Professional guidelines for assessing risk of sexual violence. Vancouver, Canada: The Mental Health, Law, and Policy Institute, Simon Fraser University.

Return to the overview of Violence Risk Assessment in Forensic Psychology.