Wyo. Stat. » Wyo. Stat. / Title 07 - Criminal Procedure / Chapter 11 - TRIAL AND MATTERS INCIDENT THERETO / Article 3 - MENTAL ILLNESS OR DEFICIENCY
Wyoming Statutes

Wyo. Stat. § 7-11-305 (2026)

Pleas of not guilty and not guilty by reason of

✓ current as of May 2026
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mental illness or deficiency; burden of proof; expert witnesses.

     (a) When a defendant couples a plea of not guilty with a
plea of not guilty by reason of mental illness or deficiency,
proof shall be submitted before the same jury in a continuous
trial on whether the defendant in fact committed the acts
charged, on the remaining elements of the alleged criminal
offense and on the issue of mental responsibility of the
defendant. In addition to other forms of verdict submitted to
the jury, the court shall submit a verdict by which the jury may
find the defendant not guilty by reason of mental illness or
deficiency excluding responsibility.

     (b) The prosecution shall prove beyond a reasonable doubt
all the elements of the offense charged. Every defendant is
presumed to be mentally responsible. The defendant shall have
the burden of going forward and proving by the greater weight of
evidence that, as a result of mental illness or deficiency, he
lacked capacity either to appreciate the wrongfulness of his
conduct or to conform his conduct to the requirements of the
law.

     (c) Only the designated examiners who examined the
defendant pursuant to W.S. 7-11-303 or 7-11-304 are competent
witnesses to testify as to the defendant's mental
responsibility.

     (d) In addition, the state and the defendant may summon
other expert witnesses who did not examine the defendant. Such
experts are not competent to testify as to the mental
responsibility of the defendant; however, they may testify as to
the validity of the procedures followed and the general
scientific propositions stated by other witnesses.

     (e) The designated examiner who examined the defendant may
testify as to and explain the nature of his examinations, his
diagnosis of mental illness or deficiency of the defendant, and
his opinion as to the defendant's ability to appreciate the
wrongfulness of his conduct or to conform his conduct to the
requirements of law. The designated examiner may be
cross-examined as to his competence and the credibility of his
diagnosis and his opinion.
Notes of Decisions
Cited in 17 cases (4 in the last 5 years), 1979–2024 · leading case: Hayes v. State, 599 P.2d 558 (Wyo. 1979).
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Hayes v. State, 599 P.2d 558 (Wyo. 1979). · cites it 30× “Anneberg's testimony was inadmissible under § 7-11-305, W.S. 1977; that it was admitted in violation of an Order in Limine; and that such was reversible error inasmuch as the evidence was insufficient to submit the case to the jury without such testimony.”
Solomon Preston Bolen v. The State of Wyoming, 2024 WY 48 (Wyo. 2024). · cites it 15× “2022) (citing Wyo. Stat. Ann. § 7-11-305 (b)). A defendant asserting the defense bears the burden of disproving the presumption that he was mentally responsible.”
Miller v. State, 755 P.2d 855 (Wyo. 1988). · cites it 9× “) [3] Section 7-11-305, W.S. 1977 (Cum.Supp. 1985), provides in part: "(b) The prosecution shall prove beyond a reasonable doubt all the elements of the offense charged.”
State v. Zespy, 723 P.2d 564 (Wyo. 1986). · cites it 18× “They found that he was not mentally responsible for his actions under § 7-11-305(b), W.S. 1977. The State determined, nevertheless, that it should proceed; and his jury trial began on January 14, 1985.”
Gabbert v. State, 420 P.3d 172 (Wyo. 2018). · cites it 10× “When a defendant pleads not guilty by reason of mental insanity, the prosecution bears the burden of proving beyond a reasonable doubt all the elements of the offense charged, while the defendant has the "burden of going forward and proving by the greater weight of evidence…”
Andrew Wayne Steplock v. The State of Wyoming, 2022 WY 12 (Wyo. 2022). · cites it 4× “” 2 Wyo. Stat. Ann. § 7-11-305 (c) states “[o]nly the designated examiners who examined the defendant pursuant to W.”
Jett Garriott Adams v. The State of Wyoming, 2023 WY 85 (Wyo. 2023). · cites it 5× “When a defendant enters a plea of not guilty by reason of mental illness or deficiency, he has the burden to prove, by a preponderance of the evidence, that as a result of that mental illness or deficiency he lacked “mental responsibility” for his criminal conduct, meaning he…”
Fulcher v. State, 633 P.2d 142 (Wyo. 1981). · cites it 4× “" Subsection (3) of this section appears as part of § 7-11-305(a), W.S. 1977, Cum.Supp. 1981: "(a) When a defendant couples a plea of not guilty with a plea of not guilty by reason of mental illness or deficiency, proof shall be submitted before the same jury in a continuous…”
Reiter v. State, 2001 WY 116 (Wyo. 2001). · cites it 2× “" The defendant is presumed to be mentally responsible, and bears the burden of proving by "the greater weight of evidence that, as a result of mental illness or deficiency, he lacked capacity either to appreciate the wrongfulness of his conduct or to conform his conduct to the…”
Polston v. State, 685 P.2d 1 (Wyo. 1984). · cites it 5× “The statute [2] providing the defense of not guilty by reason of "insanity" was repealed by the legislature with the adoption of § 7-11-305(a), W.S. 1977 [3] which substituted therefor the defense of not guilty by reason of "mental illness or deficiency.”
Anthony Rodriguez v. The State of Wyoming, 2022 WY 109 (Wyo. 2022). · cites it 4× “” Wyo. Stat. Ann. § 7-11-305 (b). Mr. Rodriguez had to disprove that presumption.”
Lewis v. State, 709 P.2d 1278 (Wyo. 1985). · cites it 4× “" Section 7-11-305(b): "(b) The prosecution shall prove beyond a reasonable doubt all the elements of the offense charged and the mental responsibility of the defendant.”
Show all 17 citing cases →
— Wyo. Stat. § 7-11-305(a) — 5 cases
Hayes v. State, 599 P.2d 558 (Wyo. 1979). “Anneberg's testimony was inadmissible under § 7-11-305, W.S. 1977; that it was admitted in violation of an Order in Limine; and that such was reversible error inasmuch as the evidence was insufficient to submit the case to the jury without such testimony.”
Fulcher v. State, 633 P.2d 142 (Wyo. 1981). “" Subsection (3) of this section appears as part of § 7-11-305(a), W.S. 1977, Cum.Supp. 1981: "(a) When a defendant couples a plea of not guilty with a plea of not guilty by reason of mental illness or deficiency, proof shall be submitted before the same jury in a continuous…”
Polston v. State, 685 P.2d 1 (Wyo. 1984). “The statute [2] providing the defense of not guilty by reason of "insanity" was repealed by the legislature with the adoption of § 7-11-305(a), W.S. 1977 [3] which substituted therefor the defense of not guilty by reason of "mental illness or deficiency.”
Engle v. State, 774 P.2d 1303 (Wyo. 1989).
Kind v. State, 595 P.2d 960 (Wyo. 1979).
— Wyo. Stat. § 7-11-305(b) — 7 cases
Miller v. State, 755 P.2d 855 (Wyo. 1988). “) [3] Section 7-11-305, W.S. 1977 (Cum.Supp. 1985), provides in part: "(b) The prosecution shall prove beyond a reasonable doubt all the elements of the offense charged.”
State v. Zespy, 723 P.2d 564 (Wyo. 1986). “They found that he was not mentally responsible for his actions under § 7-11-305(b), W.S. 1977. The State determined, nevertheless, that it should proceed; and his jury trial began on January 14, 1985.”
Lewis v. State, 709 P.2d 1278 (Wyo. 1985). “" Section 7-11-305(b): "(b) The prosecution shall prove beyond a reasonable doubt all the elements of the offense charged and the mental responsibility of the defendant.”
Brooks v. State, 706 P.2d 664 (Wyo. 1985).
Kind v. State, 595 P.2d 960 (Wyo. 1979).
— Wyo. Stat. § 7-11-305(c) — 2 cases
State v. Zespy, 723 P.2d 564 (Wyo. 1986). “They found that he was not mentally responsible for his actions under § 7-11-305(b), W.S. 1977. The State determined, nevertheless, that it should proceed; and his jury trial began on January 14, 1985.”
Solomon Preston Bolen v. The State of Wyoming, 2024 WY 48 (Wyo. 2024). “2022) (citing Wyo. Stat. Ann. § 7-11-305 (b)). A defendant asserting the defense bears the burden of disproving the presumption that he was mentally responsible.”
— Wyo. Stat. § 7-11-305(d) — 2 cases
State v. Zespy, 723 P.2d 564 (Wyo. 1986). “They found that he was not mentally responsible for his actions under § 7-11-305(b), W.S. 1977. The State determined, nevertheless, that it should proceed; and his jury trial began on January 14, 1985.”
Hayes v. State, 599 P.2d 558 (Wyo. 1979). “Anneberg's testimony was inadmissible under § 7-11-305, W.S. 1977; that it was admitted in violation of an Order in Limine; and that such was reversible error inasmuch as the evidence was insufficient to submit the case to the jury without such testimony.”
— Wyo. Stat. § 7-11-305(e) — 2 cases
Hayes v. State, 599 P.2d 558 (Wyo. 1979). “Anneberg's testimony was inadmissible under § 7-11-305, W.S. 1977; that it was admitted in violation of an Order in Limine; and that such was reversible error inasmuch as the evidence was insufficient to submit the case to the jury without such testimony.”
Jett Garriott Adams v. The State of Wyoming, 2023 WY 85 (Wyo. 2023). “When a defendant enters a plea of not guilty by reason of mental illness or deficiency, he has the burden to prove, by a preponderance of the evidence, that as a result of that mental illness or deficiency he lacked “mental responsibility” for his criminal conduct, meaning he…”
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