Although the criminal law recognizes that it is unjust to commit to trial a person who is mentally unfit or who was insane at the time of an alleged offense, the criminal justice system has had difficulty in the determination of fitness, insanity, and dangerousness. The law is not precise in its definitions of mental disorder. Mental health professionals have been used as experts in the criminal justice system, but their definitions are also imprecise. These definitional problems have an impact at every stage of the criminal justice process. The use of particular clinical diagnoses is often influenced more by institutional pressures than by scientific and clinical criteria; for example, clinicians often use a diagnosis that will achieve the court disposition they favor. Dispositions also depend on the availability of custodial and treatment facilities. The definitional problems are exemplified in efforts to define and predict dangerousness. Due to institutional pressures, clinicians err on the side of caution by overpredicting dangerousness. This circumstance suggests the reform of dangerous-offender legislation and procedures, which are based on the assumption that medical professionals do have the ability to forecast behavior reliably and accurately. 56-item reading list