K.S.A. » Chapter 21
Kansas Statutes Annotated

K.S.A. § 21-5209 (2026)

Defense of lack of mental state

✓ current as of May 2026
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21-5209. Defense of lack of mental state. It shall be a defense to a prosecution under any statute that the defendant, as a result of mental disease or defect, lacked the culpable mental state required as an element of the crime charged. Mental disease or defect is not otherwise a defense.

History: L. 2010, ch. 136, § 20; July 1, 2011.

Notes of Decisions
Cited in 22 cases (10 in the last 5 years), 2012–2024 · leading case: State v. Blansett, 435 P.3d 1136 (Kan. 2019).
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State v. Blansett, 435 P.3d 1136 (Kan. 2019). · cites it 11× “When a defendant encourages the jury to infer that the State's evidence is not credible because it failed to admit a certain piece of evidence, the State may refute the inference by informing the jury that the defense has the power to introduce evidence.”
State v. Genson, 513 P.3d 1192 (Kan. 2022). · cites it 5× “The court did not grant review of Genson's challenge to the constitutionality of K.S.A. 2020 Supp. 21-5209 or of his claims that section 5 of the Kansas Constitution Bill of Rights encompasses a right of jury nullification.”
Kahler v. Kansas, 589 U.S. 271 (2020). · cites it 2× “Suppose, for example, that the defendant shot someone dead *1026 and goes on trial for murder.”
State v. Vonachen, 476 P.3d 774 (Kan. 2020). · cites it 2× “THE INSANITY DEFENSE CLAIMS For the first time on appeal, Samuel argues he was unconstitutionally denied an ability to pursue what he characterizes as a traditional insanity defense because K.S.A. 2019 Supp. 21-5209 sets out a different approach of how to use mental disease or…”
State v. Kahler, 410 P.3d 105 (Kan. 2018). · cites it 2× “K.S.A. 2015 Supp. 21-5209. Finally, as Kleypas did here, mental illness can be asserted as a mitigator.”
State v. Cheever, 284 P.3d 1007 (Kan. 2012). “22-3220: “It is a defense to a prosecution under any statute that the defendant, as a result of mental disease or defect, lacked tire mental state required as an element of the offense charged.”
State v. Stanley, 478 P.3d 324 (Kan. 2020). “McLinn claimed the premeditation element was a required culpable mental state of the crime—in addition to the culpable mental state of intentional—which could be negated by a mental disease or defect under K.S.A. 2013 Supp. 21-5209. We engaged in a lengthy consideration of the…”
State v. Genson, 481 P.3d 137 (Kan. Ct. App. 2020). · cites it 9× “Arguing that he should not have been held criminally responsible because of his mental illness, Genson challenges the constitutionality of K.S.A. 2019 Supp. 21-5209 (stating the mental disease and defect defense) and K.”
State v. Boswell, 499 P.3d 1122 (Kan. 2021). “See K.S.A. 2020 Supp. 21-5209. The requisite mental state for premeditated first-degree murder is that the person acted intentionally.”
State v. Waterman, 540 P.3d 378 (Kan. Ct. App. 2023). · cites it 4× “Flesher's testimony was irrelevant and properly excluded by the district court under K.S.A. 2022 Supp. 21-5209, the statute governing the defense of lack of mental state.”
State v. Kirkland (Kan. Ct. App. 2022). · cites it 15× “The first asked the district court to find K.S.A. 2015 Supp. 21-5209 unconstitutional because it permits an insanity defense only to negate whatever intent the charged crime requires.”
State v. Jones (Kan. Ct. App. 2021). · cites it 10× “Jones also challenges the constitutionality of K.S.A. 2016 Supp. 21-5209 and the Kansas Sentencing Guidelines Act.”
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