The legal standard for competency to stand trial has varies from state to state. In Florida, a defendant's competency to proceed is contingent upon both sufficient present ability to consult with his or her lawyer with a reasonable degree of rational understanding and a rational or factual understanding of the proceedings against him or her. In order to provide the court with adequate information pertaining to a defendant's competency to proceed, it is important for the psychologist completing the evaluation to consider the defendant's capacity to appreciate the charges or allegations, appreciate the range and nature of possible penalties, understand the adversary nature of the legal process, disclose to his or her attorney facts pertinent to the proceeding, display appropriate courtroom behavior, and testify relevantly.

The competency to proceed evaluation consists of three separate parts. The first part of the evaluation consists of a brief social history in which the psychologist gathers information about the defendant's legal history, mental health history, employment history, school history, and substance use history. The second part of the evaluation consists of questions pertaining to the defendant's understanding of the court process and the roles of the various professionals involved with the legal system. The third part of the evaluation consists of a brief mental status examination in which the psychologist gathers information about the defendant's attention, concentration, memory, orientation, and reasoning ability. Related to the scope of information needed to form conclusions in a competency evaluation, psychological testing is rarely needed.

The requirements upon the psychologist when they offer an opinion supportive of incompetency vary from state to state. In the state of Florida, the psychologist must also address and describe three additional issues. First, the psychologist must delineate the mental illness or mental retardation thought to be responsible for the incompetency. Second, the psychologist must list the recommended treatments for the mental illness or retardation and their availability in the community and elsewhere, including a discussion of various treatment alternatives. Third, the psychologist must describe the likelihood that the defendant will attain competence after receiving the recommended treatments, and the length of time that it may take to restore the defendant to competence.