The forensic expert witness must determine the legal issue; determine the specific legal criteria (from statutes, case law, etc.) required to resolve the legal issue; conduct the clinical examination of the defendant; and apply the findings of the clinical examination to the legal criteria. It is both difficult and important to determine whether there is a causal relationship between the findings of the clinical examination and the legal criteria where competency to stand trial is at issue. These legal criteria are generally stated as whether the defendant understands the charges and can assist in the defense. It is the forensic expert's responsibility to assess disorders of mood and thinking according to criteria such as present ability, fragility of the offender's emotional state, and foreseeability of improvement in therapy and drug therapy. The right of the patient/offender to refuse treatment further complicates the process, and raises questions of malingering and feigned amnesia. In addition to the defendant's lawyer, the prosecuting attorney and, occasionally, the judge may also use the competency to stand trial issue for tactical, dispositional, or plea bargaining purposes, rather than settling the issue of competency itself. Another legal problem is the misuse of the psychiatric report when the forensic expert is unable to protect its confidentiality, despite specific statute prohibitions. Yet another troublesome matter is the use of the competency question for reasons of preventive detention, where under the guise of an unsettled legal issue, patients are kept in detention because they are felt to be too 'dangerous' to be at large. Political problems of the competency issue include the need for self-regulation by the profession to insure adequate training and qualification of experts. Recommendations for improving the quality of expert witnesses and their testimony include: careful and precise application of clinical data to the legal criteria through clear and coherent reasoning of the court report and testimony; continuing medical and in-service education; separation of psychiatrist's evaluation and treatment functions; the increased research in the areas of human behavior and the law. Thirteen references are appended.