Pierce: Montana Supreme Court Reaffirms Conduct‑Based “Knowingly” for SIWOC and Clarifies Limits on Alcohol-Use Evidence

Introduction

In State v. D. Pierce, 2025 MT 257 (Supreme Court of Montana, Nov. 12, 2025), the Court reversed a conviction for sexual intercourse without consent (SIWOC) and remanded for a new trial. The decision centers on two pivotal trial rulings:

• Jury instructions: The district court instructed the jury that the defendant acted “knowingly” if he was aware of a “high probability” that his conduct would cause a particular result—an instruction the Supreme Court has repeatedly deemed improper for sexual offenses.
• Evidentiary rulings: The district court excluded proposed defense character and habit evidence of the complainant’s prior alcohol use and, on that basis, excluded a defense expert. The Supreme Court affirmed these exclusions on the record presented, while signaling what a permissible expert proffer might look like on remand.

At trial, the State’s core theory was that K.R. was so intoxicated she was incapable of consent. Pierce’s defense emphasized that he did not know she was unable to consent, pointing to the pair’s evening messages, a phone call, her driving and activities upon returning home, and testimony that she did not appear intoxicated to several witnesses. The Supreme Court held the “high probability” mental-state instruction incorrectly lowered the State’s burden on the essential knowledge element and was not harmless given the evidence disputes. A partial dissent would have affirmed on harmless-error grounds.

Summary of the Opinion

The Court (Justice Jim Rice) reversed Pierce’s conviction and remanded for a new trial.

• Issue 1 – Mental state instruction: The district court erred by giving a result-based “knowingly” instruction that told jurors a defendant acts knowingly when aware of a “high probability” that his conduct will cause a particular result. For SIWOC, “knowingly” must be defined in conduct-based terms. Because the erroneous instruction relieved the State of proving an essential element—defendant’s awareness that the sexual intercourse was without consent or with a person incapable of consent—the error violated due process and was not harmless on this record.
• Issue 2 – Character and expert evidence: The court did not abuse its discretion by excluding character/habit evidence of K.R.’s past drinking (Rules 404 and 406) or by excluding the defense expert as proffered. The defense’s theory below framed prior drinking as a “pertinent character trait” to argue conformity on the charged occasion, which is impermissible propensity reasoning. The Court noted that a differently framed expert proffer—e.g., explaining how tolerance affects outward signs of intoxication for a non-propensity purpose—might be considered on remand if properly raised and preserved.

Justice Beth Baker, joined by Chief Justice Swanson and Justice McKinnon, concurred on the evidentiary issues but dissented on the instructional issue, concluding that the error was harmless given K.R.’s testimony that she said “stop,” Pierce’s response (“you asked for it”) and his continuing.

Analysis

Precedents Cited and Their Influence

• State v. Rowe, 2024 MT 37: The Court reiterated that sexual offenses require a conduct-based definition of “knowingly,” not a result-based one. Rowe set the analytical frame that the mental state in sexual assault crimes centers on awareness of one’s conduct, not awareness of a probabilistic “result.”
• State v. Hamernick, 2023 MT 249: A close analogue. The Court reversed where the jury was told the State need only prove the defendant was aware of a “high probability” that intercourse was without consent. Hamernick emphasizes that SIWOC is “sexual intercourse with the awareness that it is without that person’s consent,” a standard that can be inferred from circumstances but cannot be diluted into “high probability.” In Pierce, the prosecutor echoed the improper “high probability” framing in closing, reinforcing the need for reversal.
• State v. Deveraux, 2022 MT 130: Clarified that SIWOC is a conduct-based offense: the particularized conduct—engaging in intercourse without consent—defines the crime. Result-based mental-state instructions don’t fit this structure.
• State v. Gerstner, 2009 MT 303: Similar principle in sexual assault: the crime targets the act of sexual contact itself; thus, the applicable mental state is tied to awareness of conduct, not result probabilities.
• State v. Bryson, 2024 MT 315: On evidence: affirmed exclusion of a complainant’s prior drinking habits under Rules 404/406 to avoid unfair prejudice while allowing robust cross-examination about the charged incident. Bryson also confirms there is no difference in the “knowingly” requirement whether SIWOC is charged as “without consent” or “incapable of consent.”
• Standards of review and due process:
  • Jury instructions: State v. Doyle (abuse of discretion; reversible only if substantial rights affected); City of Missoula v. Zerbst (instructions that relieve the State of proving each element beyond a reasonable doubt violate due process); State v. Ilk; State v. Rothacher.
  • Evidentiary rulings: State v. Gomez; State v. Given (abuse of discretion framework).
  • Right to present a defense: State v. Johnson (1998); State v. Colburn; State v. Aguado (balance defendant’s rights and evidentiary limits; later overruled on another ground). Preservation: State v. Ferguson (cannot change theories on appeal).

Legal Reasoning

1) “Knowingly” in SIWOC is conduct-based, not result-based

Montana’s general mental-state statute provides multiple definitions of “knowingly” (Section 45-2-101(35), MCA). For sexual offenses, the Court has repeatedly held that the conduct-based definition applies. The crime of SIWOC (Section 45-5-503, MCA (2019)) makes it unlawful to “knowingly” engage in intercourse either without consent or with a person incapable of consent. The “result-based” instruction—awareness of a “high probability” of a result—does not fit this statutory structure because it reduces what the State must prove from awareness that intercourse was without consent (or with a person incapable of consenting) to mere awareness that there was a risk of that condition.

In Pierce, the trial court gave a result-based instruction: “A person acts knowingly when the person is aware there exists a high probability that the person’s conduct will cause a specific result” (Instruction 15). This deviated from Rowe, Hamernick, Deveraux, and Gerstner. The improper instruction lowered the State’s burden and risked misleading jurors to convict on a belief that Pierce only needed to perceive a high likelihood of non-consent/incapacity.

2) Why the error was not harmless here

The State conceded instructional error but argued harmlessness. The majority disagreed. The trial evidence and themes placed Pierce’s knowledge squarely in dispute:

• K.R.’s and Pierce’s messaging and a phone call occurred shortly before the encounter; K.R. drove home, carried groceries, provided her address, and left the door unlocked; several witnesses (including the SANE nurse and a friend) did not perceive her as intoxicated hours later.
• Officer testimony at trial suggested K.R. appeared intoxicated, but the officer’s initial report did not note intoxication or odor of alcohol; another witness testified K.R. did not appear intoxicated around the police encounter.
• The State advanced a theory that K.R. was “too drunk to know what was going on,” while also maintaining she unambiguously withdrew consent by saying “stop.”

Against this backdrop, telling jurors they could convict if Pierce knew there was a “high probability” of non-consent/incapacity undermined the correct burden: the State had to prove he was aware that she did not consent or was incapable of consenting. The prosecutor’s repeated reliance on “high probability” in closing amplified the prejudice. Under Montana’s due process framework, such an instruction relieves the State of its duty to prove every element beyond a reasonable doubt and affects substantial rights—triggering reversal.

The dissent would have found harmless error based on evidence that K.R. said “stop,” Pierce replied “you asked for it,” pushed her head down, continued to “finish,” and initially denied being there. The majority did not weigh evidence anew; it focused on the risk that jurors, told to apply a lower mental-state threshold, might have convicted without finding the required awareness—particularly given the disputes over K.R.’s condition, Pierce’s knowledge of it, and the timing and content of any withdrawal of consent.

3) Character, habit, and expert evidence on alcohol use

The defense sought to introduce evidence of K.R.’s prior heavy drinking through lay witnesses and an expert (Dr. George) to show she functioned at high BAC levels and “acted in conformity” with those habits on the charged night. The district court excluded the prior-drinking evidence as inadmissible character and habit proof (Rules 404/406), and excluded the expert on relevance grounds given that exclusion. The Supreme Court affirmed those rulings.

Key points:

• No propensity route: The defense explicitly argued alcohol use as a “pertinent character trait” to prove conformity. That is classic Rule 404(a) propensity reasoning and was properly excluded.
• Habit (Rule 406): The court found prior drinking was not a narrowly-defined, semi-automatic “habit” of the type Rule 406 contemplates; and even if arguable, the prejudice risk was substantial.
• Balanced approach consistent with Bryson: The court permitted robust cross-examination about K.R.’s consumption and conduct on the night in question—the facts that matter—while excluding broad character/habit evidence about alcohol use divorced from the event.
• Expert proffer and preservation: On appeal, Pierce reframed the expert’s purpose: to explain how chronic alcohol use can mask outward signs of intoxication—directly countering the State’s “obvious incapacity” theory. But the Supreme Court held that this was not the theory presented below. The defense told the trial court the expert would show K.R. “acted in conformity” with prior heavy drinking—that is, a propensity purpose. Because the non-propensity rationale was not preserved, exclusion was affirmed. The Court noted that differently framed expert testimony might be considered on remand (e.g., to rebut testimony suggesting people with high tolerance show more impairment—an assertion the Court characterized as “illogical and facially questionable”).

Impact

• Jury instructions statewide: For SIWOC and related sexual offenses, trial courts must give conduct-based “knowingly” instructions and avoid “high probability” language. Prosecutors should train on this and revise any reliance on MCJI formulations that include result-based phrasing. Defense counsel should object to any “high probability” language and preserve the issue.
• Harmless error analysis: Where the defendant’s awareness of non-consent/incapacity is meaningfully disputed—and especially when the State frames the case around “obvious intoxication”—result-based instructions are unlikely to be deemed harmless.
• Evidence of alcohol use: Broad character or habit evidence of a complainant’s prior drinking remains disfavored and likely inadmissible when used to suggest conduct in conformity. However, narrowly tailored, non-propensity expert testimony explaining how tolerance affects outward signs of impairment may be admissible to help jurors assess what a defendant reasonably could perceive—if properly disclosed, relevant, and preserved.
• Prosecutorial argument: Prosecutors should avoid anchoring closing arguments in “high probability” formulations or probabilistic routes to “knowledge.” The proper focus is defendant’s awareness that intercourse was without consent or with a person incapable of consenting.
• Training for law enforcement witnesses: Opinions about “tolerance” and observable impairment must be grounded in reliable knowledge. Unsupported assertions (e.g., that higher tolerance produces “more signs of impairment”) risk reversal or impeachment, and may now invite defense experts on remand.

Complex Concepts Simplified

• Conduct-based vs. result-based “knowingly”:
  • Conduct-based: The defendant is aware of what he is doing (his conduct). In SIWOC, the critical question is whether he was aware he was engaging in sexual intercourse without the other person’s consent or with a person incapable of consenting.
  • Result-based: The defendant is aware his conduct is highly likely to cause a particular outcome. This formulation is improper for SIWOC because it lowers the State’s burden from awareness of non-consent to awareness of risk.
• Consent and incapacity:
  • Consent means words or overt actions indicating a freely given agreement. Lack of consent can be inferred from all circumstances.
  • Incapacity (e.g., “physically helpless”) includes unconsciousness or an inability to communicate unwillingness. The State must still prove the defendant’s awareness of the absence of consent or the person’s incapacity.
• Character vs. habit evidence:
  • Character (Rule 404): Evidence of a person’s trait (e.g., being a heavy drinker) is generally inadmissible to prove they acted that way on a specific occasion.
  • Habit (Rule 406): Evidence of a person’s regular, semi-automatic response to a specific situation may be admissible to show conformity on a particular occasion. “Drinking a lot” is typically too variable to count as a habit.
• Harmless error: Even if a legal error occurred, a conviction stands if the State shows beyond a reasonable possibility that the error did not affect the verdict. Where the error lowers the State’s burden on a contested element, courts are reluctant to deem it harmless.
• Preservation: Appellate courts generally review only the theories and objections made in the trial court. If the defense wants expert testimony admitted for a non-propensity purpose, it must make that purpose clear and tie it to the issues the jury must decide.

Practical Guidance for the Remand and Future Trials

• Model approach to “knowingly” in SIWOC:
  • Give a conduct-based definition: “A person acts knowingly with respect to conduct when the person is aware of his or her conduct.”
  • Pair with an elements instruction clarifying the State’s burden: “To convict, the State must prove beyond a reasonable doubt that the defendant was aware that the sexual intercourse was without the other person’s consent or that the other person was incapable of consenting. You may infer awareness from all the facts and circumstances.”
  • Avoid “high probability” language.
• Expert testimony on alcohol tolerance:
  • Permissible purpose: Educate jurors on how chronic alcohol use may affect outward signs of impairment, bearing on what a reasonable observer could perceive, and thus on the defendant’s awareness—without arguing the complainant “acted in conformity” with a drinking trait.
  • Foundation: Qualifications, reliable principles, and fit with disputed issues (e.g., countering testimony that tolerance produces “more” observable impairment).
  • Disclosure and motion practice: Offer a clear, non-propensity rationale; identify methodologies and expected opinions; anticipate Rule 403 balancing.
• Closing arguments:
  • Prosecution: Focus on awareness that consent was absent or that the complainant was incapable of consenting; tie to concrete facts (statements, conduct, contemporaneous reactions).
  • Defense: Emphasize concrete behaviors bearing on perceived capacity and consent (communications, coordinated tasks, demeanor), and challenge any leap from BAC to obvious incapacity.

The Dissent’s Perspective

Justice Baker agreed the instruction was wrong but would have affirmed, concluding the error was harmless. She highlighted evidence that, upon K.R. saying “stop,” Pierce shoved her head down, stated “you asked for it,” continued in order to “finish,” and initially denied being at the residence—facts she viewed as foreclosing any reasonable probability of a different outcome. The majority, however, emphasized that the jury was instructed under an impermissibly lowered burden amidst disputed evidence about K.R.’s condition and Pierce’s knowledge—requiring a new trial to ensure a verdict under the correct standard.

Conclusion

State v. Pierce cements Montana’s trajectory since Gerstner, Deveraux, Rowe, and Hamernick: SIWOC is a conduct-focused crime, and “knowingly” must be defined accordingly. Result-based “high probability” instructions are substantively wrong for sexual offenses and risk violating due process by lowering the State’s burden on a central element—awareness that intercourse was without consent or with a person incapable of consenting. Where knowledge is meaningfully disputed, such an error is unlikely to be harmless.

On evidence, Pierce underscores the careful balance trial courts must strike. Courts may—and often should—exclude broad propensity or habit evidence about a complainant’s prior drinking, while allowing thorough inquiry into the charged event. At the same time, the opinion signals that expert testimony on alcohol tolerance may be admissible for a non-propensity purpose if properly grounded and preserved, particularly to counter unreliable assertions about observable impairment.

The overarching takeaways: draft SIWOC instructions in conduct-based terms, avoid probabilistic “knowledge” verbiage, litigate expert issues with precision, and preserve the correct theories. Pierce thus both reaffirms Montana’s mental-state doctrine for sexual offenses and provides practical guidance for the evidentiary and instructional pitfalls that recur in intoxication-capacity prosecutions.