Academic journal article Violence and Victims

Violence Prediction Methods: Statistical and Clinical Strategies

Academic journal article Violence and Victims

Violence Prediction Methods: Statistical and Clinical Strategies

Article excerpt

The paper suggests that the conventional wisdoms that we cannot and should not predict violence are wrong. We can predict violence, and we should predict violence. It is the unfortunate case, however, that we cannot do it very well, and this is true whether the predictions are made subjectively or statistically. Since the prediction of violence (and of other antisocial behaviors) is so pervasive in our justice and mental health systems, it is important that we attempt to do it better-that is, more efficiently and more effectively. In this paper we show that there is value to both clinical and statistical strategies toward the prediction problem, and suggest ways by which both may be improved. Attention to issues of fundamental measurement, to the base rate, to selection ratios, and to the methods of combining predictive information will be needed if the suggested improvements are to be realized. Finally, we propose that the statistician and the clinician need to pay attention to and learn from one another.

The conventional wisdom with respect to the prediction of violence is that we cannot do it. This is, of course, utter nonsense. The urban dweller who fails to cross the street after noticing a nasty-looking assemblage of young toughs on the sidewalk ahead either is very brave or very foolish. The circumspect street-crosser, on the other hand, wisely has made a prediction that violence may occur and has taken steps to avoid it. Not only can we predict violence, virtually all of us do engage in the prediction of violence. Depending upon our positions in society, the law may even require us to do so.

Out of the conventional wisdom that we cannot predict violence has arisen the ethical stricture that we may not predict violence. This too is utter nonsense. Our circumspect urban dweller, being an ethical person, followed this advice recently and promptly was mugged. On recovery and reflection, the urban dweller found the ethical principle indefensible, and returned to the prediction of violence.

It is in the consequences of prediction, not the fact of it, that ethical problems are raised. Predicting violence to himself, Bernhard Goetz prevented it not by crossing the street, but by shooting several young men on a subway train. Many feel that this response was disproportionate to the situation, and that his actions are to be condemned. And yet the Supreme Court has ruled that the death penalty may be imposed based on a prediction of future violence (Jurek v. Texas, 1976).

In our opinion, the responses of both Goetz and the Supreme Court to a prediction of violence are indefensibly extreme, because of the high likelihood of error.1 We also believe that the urban dweller who walks purposefully into the midst of a gang of young toughs is foolish-even if the act is based on a rational assessment of the low probability of attack. We feel similarly (although perhaps with more sympathy) about the urban dweller who, predicting violence on every corner, literally hides in a barricaded home. All of these are inappropriate responses to the prediction of violence. The circumspect street-crosser, we feel, has made an appropriate-and relatively benign-response to prediction.

We would propose a new "conventional wisdom." (1) We can predict violence. (2) We should predict violence. (3) Since our predictions are highly inaccurate, we should seek ways to make them better. (4) We must acknowledge that mistakes will be made when we predict, and acknowledge also that they will be made if we do not predict. (5) The ethical issue should concentrate on the consequence of prediction, but cannot be divorced from the issue of the accuracy with which we can predict.

References in support of the first proposition can be found in Gottfredson and Gottfredson (1988), Monahan (1981), and Wolfgang and Weiner (1982). Proposition (2) states an ethical position; for discussion, see Miller (1987), Miller and Morris (1988), Monahan (1981; 1982; 1984), Moore (1985), Morris and Miller (1985), Singer (1987), Tonry (1987), and Underwood (1979). …

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