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Title 10, Armed ForcesRelease 119-110

§949k Defense of Lack of Mental Responsibility

Title 10 › Subtitle A — General Military Law › PART II — PERSONNEL › CHAPTER 47A — MILITARY COMMISSIONS › SUBCHAPTER IV — TRIAL PROCEDURE › § 949k

Last updated Sep 22, 2026|Official source

Summary

Allows a person on trial by military commission to claim they lacked mental responsibility at the time of the offense because a severe mental disease or defect kept them from understanding what they were doing or that it was wrong. Mental illness by itself is not a separate defense. The accused must prove this defense by clear and convincing evidence. If the defense is raised, the judge will tell the panel to find the accused guilty, not guilty, or not guilty by reason of lack of mental responsibility. A not-guilty-by-reason verdict only happens if a majority of the members present when they vote agree the defense is proven.

Full Legal Text

Title 10, §949k

Armed Forces, Source: USLM XML via OLRC

(a)Affirmative Defense.—
It is an affirmative defense in a trial by military commission under this chapter that, at the time of the commission of the acts constituting the offense, the accused, as a result of a severe mental disease or defect, was unable to appreciate the nature and quality or the wrongfulness of the acts. Mental disease or defect does not otherwise constitute a defense.
(b)Burden of Proof.— (c) Findings Following Assertion of Defense.—
The accused in a military commission under this chapter has the burden of proving the defense of lack of mental responsibility by clear and convincing evidence.
(d)Majority Vote Required for Finding.—
The accused shall be found not guilty by reason of lack of mental responsibility under subsection (c)(3) only if a majority of the members present at the time the vote is taken determines that the defense of lack of mental responsibility has been established.

Legislative History

Notes & Related Subsidiaries

Editorial Notes

Prior Provisions

A prior section 949k, added Pub. L. 109–366, § 3(a)(1), Oct. 17, 2006, 120 Stat. 2615, related to the defense of lack of mental responsibility, prior to the general amendment of this chapter by Pub. L. 111–84.

Reference

Citations & Metadata

Citation

10 U.S.C. § 949k

Title 10, Armed Forces

Last Updated

Sep 22, 2026

Release point: 119-110