Competency to stand trial is a constitutional requirement of the due process clause of the Fourteenth Amendment. In the criminal justice system, psychologists play a crucial role in the determination of a defendant's competency whenever the issue is raised during a criminal trial. The findings of this study show that the most important predictor of judges' decisions on competency to stand trial was psychologists' evaluations. Defendants' criminal history and prior experience of incompetency adjudication also correlated with judges' adjudication on the competency of current charges. A defendant was less likely to be adjudicated as competent to stand trial if he/she previously had been found incompetent to stand trial. Demographic variables such as race had no relationship to judges' decisions. 4 tables, 6 notes, 35 references, and appended trial competency instrument and its sections and questions