Competency Screening Test (CST)

The Competency Screening Test (CST) was developed to address the unnecessary pretrial detention and commitment of individuals charged with crimes but likely to be judged fit to stand trial. This forensic instrument was designed and tested to provide objective measures based on the legal criteria for determination of a defendant’s capacity to participate in his or her own defense against criminal charges. Psychological diagnoses of mental illness or mental retardation may indicate incompetency for trial but may not be sufficient for such a finding by a court. Therefore, this test was developed to reduce the risk of inappropriate findings based on mental state alone.

The right of a person to be mentally as well as physically present to face his or her accusers was recognized as early as 1764 in British Common Law. In 1960, for the first time, the U.S. Supreme Court enunciated the constitutional requirement of competency to stand trial in Dusky v. United States (1960) and spelled out the legal standard that the defendant must have “sufficient present ability to consult with his lawyer with a reasonable degree of rational understanding” and “a rational as well as a factual understanding of the proceedings against him.”

CST Description and Development

The CST consists of 22 items in a sentence-completion format designed as a self-reporting paper-and-pencil instrument.

The content of each item relates to some aspect of the task of a defendant preparing for and going to trial as a result of criminal charges. Each item is based on a factor within the legal definition of fitness for trial and the psychological conditions that may contribute to significant impairment of that ability.

Scores on the 22 items were subjected to a factor analysis using a varimax orthogonal rotation. Six factors emerged that were consistent with the defendant’s ability to stand trial:

  1. Relationship to one’s attorney in establishing a defense
  2. Understanding and awareness of the nature of the court proceedings
  3. Affective response to the court process in dealing with accusations and feelings of guilt
  4. Judgmental qualities in engaging in the strategy and evaluation of the trial
  5. Trust and confidence in the attorney
  6. Recognition of the seriousness of the situation

Each of the 22 items is scored on a 3-point scale, from 0 to 2, based on one or more of these factors.

A response that clearly relates to one of the legal criteria receives a score of 2. Responses characterized as redundant, circular, or impoverished but not clearly inappropriate are scored 1. A zero score would be given for an answer that reveals characteristics such as self-defeating behavior, substantial disorganization, or a thought disorder that would interfere with the ability to contribute to one’s defense. For example, on Item 2, “When I go to court, the lawyer will…,” an appropriate response is “defend me” and would be scored a 2, reflecting the nature of the proceedings and the role of the attorney. A contrasting response, “put me away,” would receive a zero score. This item addresses the legal criterion of a defendant’s ability to assist an attorney in his or her own defense. The psychological referent focuses on trust and the ability to engage with another, in this case the lawyer. Understanding of the role of legal representation is also an element in this item.

Scores are summated and can total in a range from 0 to 44. Qualitative differences were found at about 20; thus, a score of 20 or below is judged as incompetency for trial. Reliability by trained researchers was .93, significant at the .001 level.

As a screening instrument, the purpose of the CST is to avoid hospitalization of those defendants who may be tested in the court and most likely deemed to be competent, rather than delay the trial of those individuals. The test results of the CST and judges’ decisions on return to trial were generally consistent. Focusing on the criteria for competency to stand trial also offered specific guidelines for making a judgment that could avoid pretrial detention. Several validation studies have followed the original test construction and research and have supported the efficacy of the CST.

Further Research

Additional research has been undertaken by psychologists to aid the courts in the assessment of fitness for trial. John Monahan and his colleagues at the University of Virginia have constructed an instrument based on the parameters of understanding, reasoning, and appreciation, consistent with the psychological underpinnings of the legal criteria for competency to stand trial.


  1. Dusky v. United States, 362 U.S. 402 (1960).
  2. Lipsitt, P. D., Lelos, D., & McGarry, A. L. (1971). Competency for trial: A screening instrument. American Journal of Psychiatry, 128(1), 105-109.
  3. Nottingham, E. J., IV, & Mattson, R. E. (1981). A validation study of the Competency Screening Test. Law and Human Behavior, 5, 329-335.
  4. Otto, R. K., Poythress, N. G., Nicholson, R. A., Edens, J. E., Monahan, J., Bonnie, R.J., et al. (1998). Psychometric properties of the MacArthur Competence Tool-Criminal Adjudication. Psychological Assessment, 10, 435-143.
  5. Randolph, J. J., Hicks, T., Mason, D. J. (1982). The Competency Screening Test: A validation study in Cook County, Illinois. Criminal Justice and Behavior, 9, 495-500.

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