Residency · Residency · Psychiatry
Competency to Stand Trial and the Insanity Defense
Introduction
Forensic psychiatry occupies the intersection of mental health and the legal system. Two of its most critical concepts are competency to stand trial (CST) and the insanity defense. Though frequently conflated by the public, they address fundamentally different legal questions: CST concerns a defendant's present mental state, while the insanity defense concerns the defendant's mental state at the time of the offense.
Competency to Stand Trial
Legal Foundation
Rooted in the Sixth Amendment right to a fair trial. Defined by Dusky v. United States (1960): the defendant must have a rational and factual understanding of the proceedings and be able to consult with counsel with a reasonable degree of rational understanding. CST is the most frequently raised forensic psychiatric issue in criminal law.
Clinical Assessment
Factual understanding: Can the defendant identify courtroom personnel, understand charges, and comprehend potential penalties? Rational understanding: Can the defendant appreciate the adversarial nature of the process and make reasoned decisions? Ability to assist counsel: Can the defendant communicate coherently, recall relevant events, and participate in the defense?
Structured Assessment Tools
MacArthur Competence Assessment Tool-Criminal Adjudication (MacCAT-CA). Competence Assessment for Standing Trial for Defendants with Mental Retardation (CAST-MR). Evaluation of Competency to Stand Trial-Revised (ECST-R).
Competency Restoration
Defendants found incompetent are typically committed for competency restoration treatment. Pharmacotherapy (usually antipsychotics) is the primary intervention. Sell v. United States (2003): involuntary medication for restoration is permissible only under strict criteria. If restoration is not achievable, civil commitment proceedings may follow.
The Insanity Defense
Historical Development
| Standard | Year | Core Test | Burden of Proof | Current Status |
|---|---|---|---|---|
| M'Naghten Rule | 1843 | Did not know nature/quality of act OR did not know it was wrong | Varies by jurisdiction | Most widely used (majority of US states) |
| Irresistible Impulse | 1887 | Could not control conduct despite knowing it was wrong | Varies | Used as supplement to M'Naghten in some states |
| Durham Rule | 1954 | Act was the "product of" mental disease or defect | Prosecution | Largely abandoned (only New Hampshire) |
| ALI/Model Penal Code | 1962 | Lacked substantial capacity to appreciate criminality OR conform conduct | Defense (preponderance) | Used in many federal circuits and some states |
| Federal (IDRA) | 1984 | Unable to appreciate nature/quality or wrongfulness | Defense (clear and convincing) | Federal courts post-Hinckley |
M'Naghten Rule (1843): defendant did not know the nature and quality of the act or did not know it was wrong. Irresistible Impulse Test: defendant could not control conduct despite knowing it was wrong. Durham Rule (1954): the act was the product of mental disease or defect (largely abandoned) Model Penal Code (ALI) Standard: defendant lacked substantial capacity to appreciate criminality or conform conduct to the law.
Current Standards by Jurisdiction
Most U.S. states use a version of M'Naghten or the ALI standard. Four states have abolished the insanity defense entirely (Kansas, Montana, Idaho, Utah) The federal standard (Insanity Defense Reform Act of 1984) requires the defendant to prove insanity by clear and convincing evidence.
Guilty but Mentally Ill (GBMI)
Alternative verdict available in some jurisdictions. Defendant is found guilty but receives mental health treatment during incarceration. Criticized as providing no meaningful legal advantage over a standard guilty verdict.
Conducting the Forensic Evaluation
Key Differences from Clinical Assessment
The evaluee is not your patient; there is no therapeutic relationship. Informed consent must include notification of the limits of confidentiality and the purpose of the evaluation. The report is prepared for the retaining attorney or the court, not for the evaluee.
Report Writing
Present findings objectively; avoid advocacy. Clearly distinguish clinical observations from forensic opinions. Address the specific legal standard of the jurisdiction.
Key Clinical Pearls
Competency is a legal determination made by the judge, not the psychiatrist; the evaluator provides an expert opinion. The insanity defense is raised in fewer than 1% of felony cases and succeeds in approximately 25% of those. Malingering must always be considered in forensic evaluations; use validity testing and collateral information. A defendant can be psychotic and still competent to stand trial if symptoms do not impair the Dusky criteria.
References
- Mossman D, Noffsinger SG, Ash P, et al. AAPL practice guideline for the forensic psychiatric evaluation of competence to stand trial. J Am Acad Psychiatry Law. 2007;35(4 Suppl):S3-S72.
- Resnick PJ, Knoll JL. Insanity defense evaluations: toward a model for evidence-based practice. Brief Treat Crisis Interv. 2005;5(1):92-110.
- Pirelli G, Gottdiener WH, Zapf PA. A meta-analytic review of competency to stand trial research. Psychol Public Policy Law. 2011;17(1):1-53.
- Appelbaum PS. Assessment of patients' competence to consent to treatment. N Engl J Med. 2007;357(18):1834-1840.