The Forensic Minute October 2025 Issue: The Insanity Defense

---

The Legal Spotlight: Gunman Found Guilty After Failed Insanity Plea

In a recent Colorado case, a mass shooter attempted an insanity defense, but jurors rejected it and convicted him. The verdict underscores a long-standing reality: despite media portrayals, insanity pleas are infrequent and rarely successful. Research shows that the defense is raised in fewer than 1% of felony cases, and of those, only about 0.25% lead to acquittals. Even then, defendants almost never go free. Most are committed to psychiatric hospitals, often for much longer than a prison sentence would have lasted.

---

Systemic Tension & Forensic Challenges

Forensic psychologists face significant challenges when evaluating insanity and diminished capacity claims, largely because legal and clinical standards don’t align neatly. Retrospective evaluations require reconstructing a defendant’s mental state at the time of the offense, often with incomplete records, divergent collateral reports, and no possibility of direct observation. A diagnosis alone is insufficient: the law requires specific findings, such as whether a defendant could appreciate the wrongfulness of their actions or form the intent necessary for a crime. This gap between clinical evidence and legal criteria leaves room for disagreement among experts and fuels debates about reform. Critics argue that the current all-or-nothing framework is too rigid, leaving some defendants with severe mental impairments unrecognized by the courts, while others worry that expanding defenses risks public safety and undermines accountability.

---

Humanizing Justice Through Insanity Evaluations

Insanity evaluations help lawyers understand what was happening in a person’s mind when a crime happened. These evaluations look at whether someone had a mental illness that made it hard for them to know what they were doing or tell right from wrong. Even if the person doesn’t meet the full rule for being legally insane, the test can show if they were struggling with serious mental health problems. This helps lawyers explain why their client acted a certain way and gives the court a better picture of what really happened. Consequently, these evaluations can be viewed as a form of legal strategy. 

Insanity evaluation, to that end, can also help reduce how much blame a person gets for their actions. A forensic psychologist might find that the person was having strong emotions, hearing voices, or seeing things that weren’t real. Lawyers can use this information to ask for a lighter sentence or for the person to get treatment instead of going to prison. Showing that the person was sick rather than simply bad helps the court see them as a human being who needs help. In sum, by connecting mental health facts to the law, these evaluations help the court make fair and informed decisions.

---

References:

American Civil Liberties Union & ACLU Foundation of Kansas. (2019, June 7). Brief of amici curiae the American Civil Liberties Union and the ACLU Foundation of Kansas in support of petitioner (No. 18-6135). Supreme Court of the United States. https://www.supremecourt.gov/DocketPDF/18/18-6135/102424/20190607173553178_18-6135%20Amicus%20Brief.pdf

Asokan, T. V. (2016). The insanity defense: Related issues. Indian Journal of Psychiatry, 58(Suppl 2), S191–S198. https://doi.org/10.4103/0019-5545.196832

Bryant, R. P., & Hume, C. B. (1977). Diminished capacity—Recent decisions and an analytical approach. Vanderbilt Law Review, 30(2), 213–236. https://scholarship.law.vanderbilt.edu/vlr/vol30/iss2/3/

Callahan, L. A., Steadman, H. J., McGreevy, M. A., & Robbins, P. C. (1991). The volume and characteristics of insanity defense pleas: An eight-state study. Bulletin of the American Academy of Psychiatry and the Law, 19(4), 331–337. https://jaapl.org/content/jaapl/19/4/331.full.pdf

Gaskell, S. (n.d.). Insanity defense psychological evaluations by Dr. Steven Gaskell. Psycholegal Assessments, Inc. https://psycholegalassessments.com/areas-of-expertise/insanity-defense-psychological-evaluations/

Grachek, J. E. (2006). The insanity defense in the twenty-first century: How recent United States Supreme Court case law can improve the system. Indiana Law Journal, 81(4), 1479–1501. https://www.repository.law.indiana.edu/ilj/vol81/iss4/14

Gruver, M. (2024, September 23). Gunman in Colorado supermarket shooting is the latest to fail with insanity defense. Associated Press. https://apnews.com/article/colorado-grocery-store-shooting-verdict-insanity-defense-5165e084ef220a9d65432a2e748979c9

Hans, V. P. (1986). An analysis of public attitudes toward the insanity defense. Criminology, 24(2), 393–414. https://doi.org/10.1111/j.1745-9125.1986.tb01502.x

Justia. (2025, October). The insanity defense in criminal law cases. Criminal Law Center. https://www.justia.com/criminal/defenses/insanity/

Moran, M. (2002). Insanity standards may vary, but plea rarely succeeds. Psychiatric News, 37(8). https://doi.org/10.1176/pn.37.8.0024

Morse, S. J. (2008). Diminished capacity. In B. L. Cutler (Ed.), Encyclopedia of psychology and law. SAGE Publications. https://doi.org/10.4135/9781412959537.n84