Many forensic psychologists appraise the risk of future violence for criminal offenders or psychiatric patients involved in the criminal justice system. There are several systems to be relied upon for adult forensic cases, and the impetus for this work began more than fifty years ago with the recognition that formulaic, mechanical or actuarial methods are more accurate than informal clinical judgement, experience and intuition, especially for violence. There are two kinds of formal (formulaic, mechanical) assessments for violence risk: actuarial and non-actuarial. The non-empirical methods, typical of such non-actuarial schemes, used in developing the HCR-20 contrast with actuarial techniques. No evidence supports the HCR-20 manual's requirements to render a final three-category judgement based on idiosyncratic factors, include a clinical interview, or regard perceived changes in so-called clinical and risk-management items as indicating altered risk.