The Two-Tiered Violence Risk Estimates (TTV) is a measure designed to assess the likelihood of future violence in offenders. It falls under the integrated-actuarial method of risk assessment, whereby an actuarial estimate is used as an anchor for the risk prediction, and dynamic risk factors are used for risk management purposes. Unlike other measures of an actuarial nature, the TTV was developed by evaluating common risk factors contained in existing risk measures, such as the Statistical Information on Recidivism Scale, as well as risk factors with a strong relation to violence in the literature. The scale was developed using a sample of 247 male offenders. Approximately half of the development sample reoffended in general, while around one third of the sample violently reoffended.

The TTV contains two subscales. The first subscale, the Actuarial Risk Estimate (ARE), consists of 10 historical items relating to an offenders’ social and criminal history. Items relating to criminal history include age of first adult conviction, number of prior incarcerations, number of prior assault convictions, community supervision failure, and criminal associations. Items relating to social history include childhood antisocial behavior, adolescent antisocial behavior, history of alcohol abuse, failure to complete high school, and interpersonal difficulties. The majority of items are dichotomously scored as present or not present, with the exception of the age at first adult conviction, number of prior incarcerations, and number of prior assault conviction items.

Total scores on the ARE range from 0 to 13. The development sample obtained a mean ARE score of 8.3 (standard deviation = 3.3) with a standard error or measurement of 1.04. These total scores are associated with probabilities of recidivism at 6 months, 1 year, 2 years, and 3 years. For example, a total score of 13 is associated with a likelihood of violent recidivism of 37% after 1 year and 55% at 3 years post-release. Confidence intervals are calculated for the total score for the ARE by adding and subtracting one point (the standard error or measurement for the measure) from the total score. The 95% confidence intervals provide the range of recidivism probabilities for the offender based on the offender’s total score. For example, if an offender scores 6 on the ARE, the offender would then have a range of probable scores from 5 to 7. A score of 5 is associated with a probability of recidivism of 3.5% at 6 months post-release, while a score of 7 would be associated with a probability of reoffending of 5.5% at the same time period. Therefore, it can be said that the probability of violent recidivism for this individual offender is between 3.5% and 5.5% within the first 6 months after release.

The second subscale, the Risk Management Indicators (RMI), consists of 13 items that have the potential to be dynamic in nature. The RMI items include aspects of the Central Eight risk factors, such as employment, substance abuse, family instability, associates, attitudes, and leisure, as well as other important dynamic risk factors, including financial, mental health, resistance to intervention, mood, social support, environment, and stressors. RMI items are scored as not present, present and requiring monitoring, or present and requiring intervention. The RMI can be periodically rescored in order to reflect changes in these dynamic factors due to treatment and interventions.

The ARE of the TTV correlates strongly with similar actuarial measures, such as the Statistical Information on Recidivism and the Violence Risk Appraisal Guide, obtaining correlation coefficients of over .60. The RMI has been shown to correlate strongly with similar dynamic measures, including the Risk Management scale of the Historical-Clinical-Risk Management-20, with correlation coefficients of over .60.

Validation research on the TTV has shown that it has moderate to high levels of predictive accuracy in predicting both general and violent recidivism in offenders. The common metric for evaluating predictive validity is with area under the curve values. This number gives the likelihood that a randomly selected reoffender will have a higher score than a randomly selected non-reoffender. The ARE has obtained area under the curve values between .63 and .80 for violent recidivism and between .62 and .73 for general recidivism. The RMI has shown similar results in validation studies, obtaining area under the curve values between .58 and .80 for violent recidivism and between .62 and .75 for general recidivism. The interrater reliability of the TTV is high, with an intraclass correlation coefficient over .90 for both the ARE and the RMI. The TTV has yet to be validated in more diverse populations, for example, Aboriginal or female offenders.

### References:

- Cheston, J., Mills, J. F., & Kroner, D. G. (2007, June).
*The two-tiered violence risk estimates: Preliminary validity of a dynamic-actuarial approach to measuring and managing violence risk*. Poster session presented at the North American Correctional and Criminal Justice Psychology Conference, Ottawa, Canada. - Churcher, F. P., Mills, J. F., & Forth, A. E. (2016). The predictive validity of the Two-Tiered Violence Risk Estimates Scale (TTV) in a long-term follow-up of violent offenders.
*Psychological Services, 13*, 232. - Glover, A., Churcher, F., Gray, A., Mills, J. F., & Nicholson, D. (2017). A cross-validation of the violence risk appraisal guide-revised within a correctional sample.
*Law and Human Behavior, 41*, 507–518. doi:10.1037/lhb0000257 - Mills, J. F., & Gray, A. L. (2013). Two-tiered violence risk estimates: A validation study of an integrated actuarial risk assessment instrument.
*Psychological Service*s*,**10*, 361–371. doi:10.1037/a0032608 - Mills, J. F., Kroner, D. G., & Morgan, R. D. (2011).
*Clinician’s guide to violence risk assessment.*New York, NY: Guilford Press.