Competency to stand trial is a long-established legal principle in the U.S. criminal justice system that ensures that a criminal defendant’s right to a fair trial is protected. Fundamental justice requires that criminal defendants should be able to understand the charges against them, appreciate the nature and range of penalties, and communicate with their attorney. If they do not have the capacity in any of these areas, they may be found incompetent to proceed and the judicial proceedings are suspended until they are treated and competency is restored. While competency to stand trial is the most commonly used term, competency in the criminal trial process encompasses all stages of participation in the legal process, including pretrial, trial, sentencing, and appeals. It is also a consideration if a defendant chooses to represent him or herself. Indeed, the term itself is misleading because few defendants actually go to trial, as the vast majority of cases are resolved through plea bargaining. The competency issue is raised when an officer of the court (defense, prosecution, or judge) has reason to believe there is a bona fide doubt as to a defendant’s competence. Once raised, defendants are typically referred for an evaluation by a mental health professional. Legal precedence has established that the basis of a finding of incompetency must be the presence of a major mental illness or substantial cognitive deficit. However, the mere presence of either of these conditions is not sufficient, as a functional approach to assessing competency dictates that the mental illness or cognitive deficit must be shown to affect the defendant’s specific legal competencies. It is entirely possible, for example, that some defendants with a psychosis or other severe mental illness may nevertheless be able to proceed with their case if the mental illness does not impair the legal abilities necessary to go forward.