10 USC § 850a - Art. 50a. Defense of lack of mental responsibility

---
identifier: "/us/usc/t10/s850a"
source: "usc"
legal_status: "official_legal_evidence"
title: "10 USC § 850a - Art. 50a. Defense of lack of mental responsibility"
title_number: 10
title_name: "ARMED FORCES"
section_number: "850a"
section_name: "Art. 50a. Defense of lack of mental responsibility"
chapter_number: 47
chapter_name: "UNIFORM CODE OF MILITARY JUSTICE"
subchapter_number: "VII"
subchapter_name: "TRIAL PROCEDURE"
part_number: "II"
part_name: "PERSONNEL"
positive_law: true
currency: "119-84"
last_updated: "2026-04-17"
format_version: "1.1.0"
generator: "[email protected]"
source_credit: "(Added Pub. L. 99–661, div. A, title VIII, § 802(a)(1), Nov. 14, 1986, 100 Stat. 3905; Pub. L. 114–328, div. E, title LVII, § 5233, Dec. 23, 2016, 130 Stat. 2915.)"
---


# § 850a. Art. 50a. Defense of lack of mental responsibility

**(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.

---

**Source Credit**: (Added Pub. L. 99–661, div. A, title VIII, § 802(a)(1), Nov. 14, 1986, 100 Stat. 3905; Pub. L. 114–328, div. E, title LVII, § 5233, Dec. 23, 2016, 130 Stat. 2915.)

## Editorial Notes

### Amendments

2016—Subsec. (c). , 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 Amendment

Amendment by  effective on , as designated by the President, with implementing regulations and provisions relating to applicability to various situations, see  and Ex. Ord. No. 13825, set out as notes under .

### Effective Date

> “
> 
> , 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 [
> 
> ].”

, , , provided that: