While there are many different methods of risk assessment, they tend to fall into two broad categories: clinical and actuarial (Milner & Campbell, 1995; Grubin, 1999). Clinical prediction requires the observation of an offender by a psychiatrists or a psychologist; clinicians assess risk based on their professional training, theoretical knowledge and experience with offenders. Actuarial (or statistical) prediction, 'involves predicting an individual's behavior on the basis of how others have acted in similar situations...or an individual's similarity to members of violent groups' (Milner & Campbell, 1995, p. 21). Actuarial prediction involves the use of statistical models and risk factor tools. The following is a brief description of these two assessment methods, accompanied by a discussion of the accuracy of each.