Pa. Cons. Stat. » 18 Pa. Cons. Stat. (CRIMES AND OFFENSES) / Chapter 3
Pennsylvania Consolidated Statutes

18 Pa. Cons. Stat. § 315 (2026)

 Insanity.

✓ current as of May 2026
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§ 315.  Insanity.

(a)  General rule.--The mental soundness of an actor engaged in conduct charged to constitute an offense shall only be a defense to the charged offense when the actor proves by a preponderance of evidence that the actor was legally insane at the time of the commission of the offense.

(b)  Definition.--For purposes of this section, the phrase "legally insane" means that, at the time of the commission of the offense, the actor was laboring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing or, if the actor did know the quality of the act, that he did not know that what he was doing was wrong.

(Dec. 15, 1982, P.L.1262, No.286, eff. 90 days)

 

1982 Amendment.  Act 286 added section 315. Section 4 of Act 286 provided that Act 286 shall apply to all indictments or informations filed on or after the effective date of Act 286.

Notes of Decisions
Cited in 54 cases (10 in the last 5 years), 1984–2025 · leading case: Commonwealth v. Smith, 17 A.3d 873 (Pa. 2011).
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Commonwealth v. Smith, 17 A.3d 873 (Pa. 2011). · cites it 4× “Although Appellant mentions that his mental impairments could have provided a defense of insanity, see Appellant's Brief at 44, he has not developed this assertion in any meaningful way. In order to prevail on an insanity defense, Appellant must prove by a preponderance of the…”
Commonwealth v. Reilly, 549 A.2d 503 (Pa. 1988). · cites it 8× “The issue presented in this appeal is whether section 315 of the Pennsylvania Crimes Code, 18 Pa.C.S. § 315, [1] which places the burden of proving insanity upon the criminal defendant by a preponderance of the evidence, violates Article I, section 9 of the Pennsylvania…”
Commonwealth v. Andrews, 158 A.3d 1260 (Pa. Super. Ct. 2017). · cites it 2× “18 Pa. C.S. § 315(a); see Hatfield, 579 A.”
Commonwealth v. Sanchez, 36 A.3d 24 (Pa. 2011). · cites it 2× “18 Pa.C.S. § 315; see, e.g., Commonwealth v.”
Clark v. Arizona, 548 U.S. 735 (2006). · cites it 2× “ARIZONA Opinion of the Court tive incapacity test,13 and 10 (including Arizona) have adopted the moral incapacity test alone.14 Fourteen juris dictions, inspired by the Model Penal Code,15 have in place an amalgam of the volitional incapacity test and some variant of the moral…”
Commonwealth v. Trill, 543 A.2d 1106 (Pa. 1988). · cites it 4× “Trill complains that the word "not" should have been omitted in accordance with 18 Pa.C.S. § 315(b), and the Pennsylvania Suggested Standard Jury Instructions.”
Commonwealth v. Frey, 904 A.2d 866 (Pa. 2006). · cites it 4× “" 18 Pa.C.S. § 315(a). Consistent with the common law M'Naughten test for legal insanity, Section 315(b) defines "legally insane" as "laboring under such a defect of reason, from disease of the mind, as not to know" either: (1) the nature and quality of the act; or (2) that the…”
Commonwealth v. Andre, 17 A.3d 951 (Pa. Super. Ct. 2011). · cites it 2× “” 18 Pa.C.S. § 315. As our Pennsylvania Suggested Standard Jury Instructions provide, “Stated more simply, a person is legally insane if at the time of committing an alleged crime that person is, as the result of mental disease or defect, either incapable of knowing what he or…”
Commonwealth v. Christy, 656 A.2d 877 (Pa. 1995). · cites it 2× “Appellant's evidence at the PCRA hearing was that he suffers from a "personality disorder" and has an "anti-social personality.”
Commonwealth v. Hughes, 865 A.2d 761 (Pa. 2004). “See 18 Pa.C.S. § 315(b). Thus, the PCRA court erred in viewing the competency determination as necessarily negating a defense of insanity.”
Commonwealth v. Terry, 521 A.2d 398 (Pa. 1987). · cites it 2× “18 Pa.C.S. § 315. [15] Because we determine that the expert testimony in this case is not relevant or competent under Pennsylvania law to establish the defense of lack of capacity to premeditate and deliberate, we need not and do not express an opinion concerning the…”
Commonwealth v. Baumhammers, 92 A.3d 708 (Pa. 2014). “See 18 Pa.C.S. § 315(a) (allocating the burden to the defendant to prove insanity); N.”
Show all 54 citing cases →
— 18 Pa. Cons. Stat. § 315(B) — 1 case
State v. Herrera, 1999 UT 64 (Utah 1999).
— 18 Pa. Cons. Stat. § 315(a) — 13 cases
Commonwealth v. Andrews, 158 A.3d 1260 (Pa. Super. Ct. 2017). “18 Pa. C.S. § 315(a); see Hatfield, 579 A.”
Commonwealth v. Sanchez, 36 A.3d 24 (Pa. 2011). “18 Pa.C.S. § 315; see, e.g., Commonwealth v.”
Commonwealth v. Baumhammers, 92 A.3d 708 (Pa. 2014). “See 18 Pa.C.S. § 315(a) (allocating the burden to the defendant to prove insanity); N.”
Commonwealth v. Frey, 904 A.2d 866 (Pa. 2006). “" 18 Pa.C.S. § 315(a). Consistent with the common law M'Naughten test for legal insanity, Section 315(b) defines "legally insane" as "laboring under such a defect of reason, from disease of the mind, as not to know" either: (1) the nature and quality of the act; or (2) that the…”
Commonwealth v. Reilly, 549 A.2d 503 (Pa. 1988). “The issue presented in this appeal is whether section 315 of the Pennsylvania Crimes Code, 18 Pa.C.S. § 315, [1] which places the burden of proving insanity upon the criminal defendant by a preponderance of the evidence, violates Article I, section 9 of the Pennsylvania…”
— 18 Pa. Cons. Stat. § 315(b) — 21 cases
Commonwealth v. Trill, 543 A.2d 1106 (Pa. 1988). “Trill complains that the word "not" should have been omitted in accordance with 18 Pa.C.S. § 315(b), and the Pennsylvania Suggested Standard Jury Instructions.”
Commonwealth v. Andrews, 158 A.3d 1260 (Pa. Super. Ct. 2017). “18 Pa. C.S. § 315(a); see Hatfield, 579 A.”
Commonwealth v. Hughes, 865 A.2d 761 (Pa. 2004). “See 18 Pa.C.S. § 315(b). Thus, the PCRA court erred in viewing the competency determination as necessarily negating a defense of insanity.”
Commonwealth v. Jermyn, 533 A.2d 74 (Pa. 1987).
Commonwealth v. Eichinger, J., Aplt, 108 A.3d 821 (Pa. 2014).
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