False Precision in Violence Risk Testimony: Saying More Than the Method Supports

Stephan M. Carlson, MD, MBA, FAPA · Violence and Threat Risk

A violence risk instrument sorts a person into a group and reports how often, over a defined window, people in that group were later violent. The witness who converts that group rate into "this individual is 87% likely to reoffend" has not added precision—he has invented it, and the invention is usually where the opinion breaks. What a risk instrument actually produces Most structured violence risk tools fall into two families, and neither delivers an individualized probability. Actuarial instruments place a subject into a risk bin and report the recidivism rate for the validation sample in that bin—a group frequency, bounded by wide confidence intervals at the individual level. Structured p

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