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Title 10, Armed ForcesRelease 119-102

§850a Art. 50a. Defense of Lack of Mental Responsibility

Title 10 › Subtitle A — General Military Law › PART II — PERSONNEL › CHAPTER 47 — UNIFORM CODE OF MILITARY JUSTICE › SUBCHAPTER VII — TRIAL PROCEDURE › § 850a

Last updated Aug 21, 2026|Official source

Summary

A person at a court-martial can claim that, because of a severe mental illness or defect at the time, they could not understand what they were doing or that it was wrong. Mental illness by itself is not enough. The accused must prove this claim by clear and convincing evidence. If this issue is raised, the judge must tell the court—or decide if it is a judge-only trial—to find the accused guilty, not guilty, or not guilty only because they lacked mental responsibility. A majority of members present, or the sole judge in a judge-only trial, must agree the defense is proved for that not-guilty finding.

Full Legal Text

Title 10, §850a

Armed Forces, Source: USLM XML via OLRC

(a)It is an affirmative defense in a trial by court-martial 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)The accused has the burden of proving the defense of lack of mental responsibility by clear and convincing evidence.
(c)Whenever lack of mental responsibility of the accused with respect to an offense is properly at issue, the military judge shall instruct the members of the court as to the defense of lack of mental responsibility under this section and charge them to find the accused—
(1)guilty;
(2)not guilty; or
(3)not guilty only by reason of lack of mental responsibility.
(d)Subsection (c) does not apply to a court-martial composed of a military judge only. In the case of a court-martial composed of a military judge only, whenever lack of mental responsibility of the accused with respect to an offense is properly at issue, the military judge shall find the accused—
(1)guilty;
(2)not guilty; or
(3)not guilty only by reason of lack of mental responsibility.
(e)Notwithstanding the provisions of section 852 of this title (article 52), the accused shall be found not guilty only by reason of lack of mental responsibility if—
(1)a majority of the members of the court-martial present at the time the vote is taken determines that the defense of lack of mental responsibility has been established; or
(2)in the case of a court-martial composed of a military judge only, the military judge determines that the defense of lack of mental responsibility has been established.

Legislative History

Notes & Related Subsidiaries

Editorial Notes

Amendments

2016—Subsec. (c). Pub. L. 114–328, in introductory provisions, struck out “, or the president of a court-martial without a military judge,” after “the military judge”.

Statutory Notes and Related Subsidiaries

Effective Date

of 2016 AmendmentAmendment by Pub. L. 114–328 effective on Jan. 1, 2019, as designated by the President, with implementing

Regulations

and provisions relating to applicability to various situations, see section 5542 of Pub. L. 114–328 and Ex. Ord. No. 13825, set out as notes under section 801 of this title.

Effective Date

Pub. L. 99–661, div. A, title VIII, § 802(b), Nov. 14, 1986, 100 Stat. 3906, provided that: “Section 850a of title 10, United States Code, as added by subsection (a)(1), shall apply only to offenses committed on or after the date of the enactment of this Act [Nov. 14, 1986].”

Reference

Citations & Metadata

Citation

10 U.S.C. § 850a

Title 10, Armed Forces

Last Updated

Aug 21, 2026

Release point: 119-102