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Prediction of Crime and Recidivism - Statistical Prediction

risk percent violent violence

Here we consider four studies representative of the best of actuarial prediction. Ernst Wenk, James Robison, and Gerald Smith in 1972 reviewed several massive studies on the prediction of violent crime undertaken in the California Department of Corrections. One study, begun in 1965, attempted to develop a "violence prediction scale" to aid in parole decision-making. The predictive items employed included commitment offense, number of prior commitments, heroin use, and length of imprisonment. When validated against discovered acts of actual violent crime by parolees, the scale was able to identify a small class of offenders (less than 3 percent of the total) of whom 14 percent could be expected to be violent. The probability of violence for this class was nearly three times greater than that for parolees in general, only 5 percent of whom, by the same criteria, could be expected to be violent. However, 86 percent of those identified as potentially violent were not, in fact, discovered to have committed a violent crime while on parole.

The State of Michigan Department of Corrections in 1978 introduced an actuarial prediction device, the Assaultive Risk Screening Sheet, for use in program assignment and parole decision-making. Data on 350 variables were collected for over two thousand male inmates released on parole for an average of fourteen months in 1971. Statistical analyses were performed on the data for half the subjects to derive an actuarial table relating to arrest for a new violent crime while on parole. The resulting factors were then applied to the other half of the subjects in order to validate the predictive accuracy of the scale. The six items in the table were: "crime description fits robbery, sex assault, or murder," "serious institutional misconduct," "first arrest before 15th birthday," "reported juvenile felony," "crime description fits any assaultive felony," and "ever married." Using combinations of these items it was possible to place the offenders into five discrete categories: very low risk (2.0 percent recidivism), low risk (6.3 percent), middle risk (11.8 percent), high risk (20.7 percent), and very high risk (40.0 percent).

A noteworthy advance in the development of actuarial risk assessment to predict violence in the community was reported by Quinsey, Harris, Rice, and Cormier. A sample of over six hundred men who were either treated or administered a pretrial assessment at a maximum security forensic hospital in Canada served as subjects. All had been charged with a serious criminal offense. A wide variety of predictive variables were coded from institutional files. The criterion variable was any new criminal charge for a violent offense, or return to the institution for an act that would otherwise have resulted in such a charge. The average time at risk after release was almost seven years. Twelve variables were identified for inclusion in the final statistical prediction instrument, including an offender's score on the Hare Psychopathy Checklist, alcohol abuse, and elementary school maladjustment. If the scores on this instrument were dichotomized into "high" and "low," the results indicated that 55 percent of the "high scoring" subjects committed violent recidivism, compared with 19 percent of the "low scoring" group.

Along these lines, a major meta-analysis of actuarial risk factors for crime and violence among mentally disordered offenders, (Bonta, Law, and Hanson) found those risk factors to be remarkably similar to well-known risk factors among the general offender population:

Criminal history, antisocial personality, substance abuse, and family dysfunction are important for mentally disordered offenders as they are for general offenders. In fact, the results support the theoretical perspective that the major correlates of crime are the same, regardless of race, gender, class, and the presence or absence of mental illness (p. 139).

Finally, Steadman and colleagues studied actuarial risk assessment among a sample of men and women discharged into the community from acute psychiatric facilities. Using 134 risk factors measured in the hospital, they were able to classify approximately three-quarters of the patients into one of two risk categories. "High violence risk" patients were defined as being at least twice as likely as the average patient to commit a violent act within the first twenty weeks following hospital discharge. "Low violence risk" patients were defined as being at most half as likely as the average patient to commit a violent act within the first twenty weeks following hospital discharge. Since 18.7 percent of all patients committed at least one violent act toward another during this period, this meant that high violence risk patients had at least a 37 percent likelihood of being violent and low violence risk patients had at most a 9 percent likelihood of being violent. The actual rate of violence observed in the high risk group was 44 percent and in the low risk group was 4 percent.

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