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.
For the intern
If consulted at 3am about a patient in custody claiming incompetence, immediate action is rarely needed unless there's acute agitation or suicidality requiring crisis intervention. Document the patient's current mental state and ability to communicate, then defer formal forensic evaluation until morning when you can obtain collateral records and consult attending staff. Competency and insanity evaluations are complex assessments requiring structured protocols—not emergency determinations. Remember: you're documenting clinical observations, not making legal judgments about competency or criminal responsibility.
Common pitfalls
- Confusing competency to stand trial (CST) with the insanity defense—CST addresses present ability to participate in proceedings, while insanity concerns mental state at the time of the offense. They're evaluated at different time points and answer different legal questions.
- Assuming psychosis equals incompetence—many psychotic defendants retain factual and rational understanding of proceedings per Dusky standards. Competency hinges on functional abilities, not diagnosis alone.
- Forgetting this isn't a therapeutic relationship—you must clearly inform evaluees that confidentiality is limited, your role serves the court or retaining attorney, and your findings will be disclosed in legal proceedings.
- Making the ultimate legal determination—stating "the defendant is competent" oversteps your role. Provide clinical data and expert opinion addressing legal criteria; judges make competency determinations.
Make it stick
Imagine you're covering the inpatient psychiatry service. A public defender calls you, concerned about their client who was just admitted after being arrested for assault and is now refusing to speak, claiming "the government is listening to my thoughts." The defender asks if their client is "insane" and therefore can't go to court. This is your chance to shine. You recognize that "insane" is a lay term, and the legal question is likely about Competency to Stand Trial (CST), not the insanity defense. You explain that CST evaluates their current ability to understand the court proceedings and assist their lawyer, while the insanity defense would assess their mental state at the time of the alleged assault. You also clarify that a mental illness doesn't automatically mean someone is incompetent.
If you remember one thing
Competency to Stand Trial (CST) assesses a defendant's current mental capacity to participate in legal proceedings, while the insanity defense evaluates their mental state at the time of the alleged crime. Your role as a clinician is to provide expert opinion on the functional abilities related to these legal standards, not to make the ultimate legal determination.