A Duty to Cure Jury Confusion on Elements: United States v. Kirby (10th Cir. 2025)

Introduction

In United States v. Kirby, No. 24-7070 (10th Cir. Dec. 16, 2025), the Tenth Circuit vacated a federal involuntary manslaughter conviction arising from a fatal motorcycle crash in Indian Country because the district court refused to clarify a deliberating jury’s explicit confusion about a core element of the offense. The case squarely addresses a recurring trial problem: when a jury asks, in plain terms, what a legal element means, and binding law supplies a clear answer, may the court simply tell the jurors to “re-read the instructions”?

The panel (Judge Phillips writing for the court, joined by Judge Matheson, with Judge Rossman concurring) held that under such circumstances the district court has an affirmative duty to resolve the confusion “with concrete accuracy,” drawing heavily on Bollenbach v. United States, 326 U.S. 607 (1946), and prior Tenth Circuit decisions. Because Oklahoma law clearly defines “under the influence” in DUI cases to require actual impairment of driving ability—not mere presence of intoxicants in the blood—and because the trial court declined to give that definition when the jury directly asked for it, the court found an abuse of discretion that was not harmless.

The opinion thus refines Tenth Circuit doctrine on supplemental jury instructions in criminal trials and clarifies how federal courts must handle state-law elements incorporated into federal offenses tried in Indian Country.

Summary of the Opinion

• Parties and posture. Danny Gene Kirby, an enrolled tribal member, was convicted in the Eastern District of Oklahoma of involuntary manslaughter in Indian Country, 18 U.S.C. §§ 1112, 1151, 1153, based on an underlying Oklahoma misdemeanor DUI offense: driving under the combined influence of alcohol and other intoxicating substances. He appealed his conviction to the Tenth Circuit under 28 U.S.C. § 1291.
• Facts in brief. After an afternoon drinking at Lake Eufaula and a brief motorcycle ride, Kirby lost control on a dark curve; his passenger and girlfriend, S.B., was thrown and later died. His blood alcohol content was 0.028 (well below the per se 0.08 limit), and toxicology showed several drugs, but the forensic toxicologist could not say he was impaired at the time of the crash.
• The jury’s question. During deliberations, the jury asked whether “under the influence” meant:
  • (a) it is unlawful so long as the substances are in his system, or
  • (b) the jury must determine whether he was actually affected by the substances to be impaired/unlawful.
  Defense counsel urged the court to clarify that Oklahoma law requires impairment rendering a person incapable of safely driving. The court instead told the jury: “You have all the instructions you need to return a verdict.”
• Holding. The Tenth Circuit held:
  • The district court abused its discretion by failing to answer the jury’s explicit legal question on a central element when a clear Oklahoma definition of “under the influence” was available.
  • The error was not harmless even under the more government-friendly nonconstitutional harmless-error standard; the government could not show by a preponderance that the error did not contribute to the guilty verdict.
  • The conviction was therefore vacated and the case remanded for further proceedings.
• Concurring opinion. Judge Rossman concurred in full but emphasized that, in general, district courts retain broad discretion to refer juries back to existing instructions; the duty to provide a new instruction arises only in limited circumstances—where there is clear jury confusion about a central issue and a clear legal answer not already supplied.

Analysis

1. Background: The Charge and the Trial

(a) The underlying federal and state law

Kirby was indicted for involuntary manslaughter in Indian Country under 18 U.S.C. § 1112(a), which criminalizes:

“the unlawful killing of a human being without malice … in the commission of an unlawful act not amounting to a felony.”

Because the offense occurred in Indian Country and involved an Indian defendant, 18 U.S.C. § 1153 (the Major Crimes Act) applied. For the underlying “unlawful act not amounting to a felony,” the government relied on an Oklahoma misdemeanor DUI provision:

Okla. Stat. tit. 47, § 11-902(A)(5): driving “under the combined influence of alcohol and any other intoxicating substance which may render such person incapable of safely driving or operating a motor vehicle.”

Thus, whether Kirby was guilty of involuntary manslaughter under the “unlawful act” theory turned on whether he was “under the combined influence” within the meaning of Oklahoma law at the time he was driving.

(b) Evidence of intoxication and impairment

• Kirby drank several beers; one friend saw him take a single puff from a marijuana vape, though others did not.
• Witnesses agreed he appeared sober when the group left the lakeside bar; he rode at or below the speed limit.
• At the crash scene, the trooper observed nervousness, anxiety, bloodshot eyes, an odor of alcohol, fumbling with a wallet, and agitation. Kirby declined some field sobriety tests but agreed to a breathalyzer and blood draw.
• The blood test later revealed:
  • BAC of 0.028%;
  • Two opiates, an amphetamine, two antidepressants, and three marijuana-related drugs.
• The forensic toxicologist could not opine to a reasonable degree of certainty that Kirby was impaired at the time of the accident.

Thus, there was clear evidence of ingestion of intoxicants, but ambiguous evidence of actual impairment affecting safe driving.

(c) The two theories of involuntary manslaughter

The indictment and instructions gave the jury two alternative routes to an involuntary manslaughter conviction:

1. Unlawful act theory: killing S.B. while committing the Oklahoma DUI offense (driving under the combined influence of alcohol and other intoxicating substances); or
2. Lawful act in an unlawful manner theory: killing S.B. while engaging in a lawful act (driving) in an unlawful manner or without due caution and circumspection.

The jury ultimately convicted only on the first theory and unanimously rejected the alternate negligence-based theory, a fact the panel later read as supporting the conclusion that the jury was not convinced Kirby was unable to drive safely.

2. The Critical Issue: The Jury’s Question About “Under the Influence”

The instructions incorporated the statutory language and told the jury it must decide whether Kirby was driving “under the combined influence of alcohol and any other intoxicating substance which may render such person incapable of safely driving or operating a motor vehicle.”

After several hours of deliberations and after receiving a supplemental instruction on a different issue (gross vs. ordinary negligence), the jury posed a focused legal question:

“When stating under the influence, does this mean that as long as it is in his system it is unlawful or do we need to determine if he was affected by substances to be impaired or unlawful?”

Defense counsel argued that Oklahoma law required actual impairment—being rendered incapable of safely operating the vehicle—and proposed clarifying language to that effect. The trial judge:

• Expressed concern that answering would “participat[e] too much” in deliberations;
• Feared “interpreting” the statute and deviating from its text;
• Noted that the jury had used the term “impaired,” which did not appear in the statute;
• Concluded that the initial instructions “track[ed] the statute” and that whether there was any difference between Kirby’s proposed wording and the statute was “not for [him] to decide.”

The court therefore responded simply: “You have all the instructions you need to return a verdict.” Minutes later, the jury returned a guilty verdict on the DUI-based involuntary manslaughter theory.

3. Precedents Cited and Their Influence

(a) Bollenbach v. United States, 326 U.S. 607 (1946)

Bollenbach is the Supreme Court’s foundational case on a trial judge’s responsibility to respond to jury questions. There, the jury in a federal conspiracy case twice expressed confusion about whether the defendant’s post-transportation conduct could make him guilty of conspiracy to transport stolen securities. The district court provided an erroneous and confusing answer, leading to a quick guilty verdict.

The Supreme Court reversed, articulating several key principles that drive the Kirby decision:

• The judge is “the governor of the trial” and has a duty to “assur[e] its proper conduct and [to] determin[e] questions of law.”
• “[T]he judge’s last word is apt to be the decisive word.” If it is “misleading,” a correct but “unilluminating abstract charge” earlier in the trial does not cure the harm.
• Most notably:

  “When a jury makes explicit its difficulties a trial judge should clear them away with concrete accuracy.”

• A conviction may not rest on “an equivocal direction to the jury on a basic issue.”

Kirby invokes these passages to underscore that the trial court cannot remain neutral when the jury clearly signals confusion about an element of the offense and a correct, concrete answer is readily available.

(b) United States v. Zimmerman, 943 F.2d 1204 (10th Cir. 1991)

In Zimmerman, a jury deliberating in a conspiracy case asked whether a person who observes a crime has a legal duty to report or stop it and whether failure to do so makes that person a participant in the crime. The trial judge, despite recognizing the question went to the “heart of the conspiracy concept,” merely referred the jury back to the existing instructions.

On appeal (under plain-error review), the Tenth Circuit reversed, holding:

• The jury’s question indicated genuine confusion about a central point of law.
• There was a clear legal answer: there is no general legal duty to report or stop a crime.
• Under Bollenbach, the court had an obligation to “clear away” the confusion; failure to do so risked a conviction “based on an incorrect legal basis.”

Kirby draws on Zimmerman to reinforce that it is insufficient for a court to direct jurors back to an instruction that, though legally correct in the abstract, does not actually answer their concrete legal question about how to apply the law to the facts.

(c) United States v. Duran, 133 F.3d 1324 (10th Cir. 1998)

In Duran, the defendant raised an entrapment defense. The jury repeatedly asked whether a confidential informant counted as a government “agent” for the purposes of entrapment. The court failed to define “agent,” leaving the jury with the mistaken impression that an “agent” must be a formal government employee.

The Tenth Circuit held:

• The jury’s questions “made clear” it was confused about “the legal contours of the entrapment defense.”
• The court should have defined “agent” to make clear that it includes an informant acting at the government’s direction.
• “Vague answers or mere exhortations to continue deliberating are plainly inadequate” when the jury displays misunderstanding of “relevant legal principles.”

Duran thus supplies a Tenth Circuit–specific restatement of the Bollenbach rule, which Kirby quotes and applies directly.

(d) United States v. Ness, 124 F.4th 839 (10th Cir. 2024)

Ness is cited as a contrast. There, the indictment alleged unlawful firearm possession “[o]n or about” a certain date. The pattern jury instruction defined “on or about” as “reasonably near” that date. The jury, faced with social media evidence from months earlier, asked how far back “on or about” extended. The court answered only that the jury had all the evidence it needed.

On appeal, the Tenth Circuit:

• Agreed the court’s response was “nonresponsive,” but
• Held that the judge properly refused to go beyond the pattern “reasonably near” language, because any more specific definition (e.g., “within a few weeks”) would have been legally inaccurate; the phrase is inherently context-dependent.

Kirby distinguishes Ness on a crucial ground: in Ness there was no single, clearly correct, more concrete legal answer the judge could have given; in Kirby there was.

Thus, the court in Kirby articulates an important limiting principle: the duty to supplement arises only where:

1. the jury’s question reveals genuine confusion about a central legal point, and
2. a clear, controlling legal answer exists that can concretely resolve the confusion.

(e) Oklahoma DUI precedents on “under the influence”

A significant part of the opinion is devoted to demonstrating that Oklahoma law clearly defines “under the influence” for DUI purposes. Key cases include:

• Gault v. State, 274 P. 687 (Okla. Crim. App. 1929) – equates “under the influence” with “drunk” for purposes of driving offenses.
• Luellen v. State, 81 P.2d 323 (Okla. Crim. App. 1938) – rejects the idea that DUI statutes attach guilt to any slight influence of alcohol:

  “[D]riving an automobile under the influence of intoxicating liquor does not [mean] any degree of influence, however slight; the defendant must be under such influence that it affects, to an appreciable degree, his ability to drive safely.”

  The court adopted a widely cited definition, now standard in Oklahoma law:

  An individual is “under the influence” when alcohol or drugs “has so far affected the nervous system, brain or muscles of the driver … as to impair, to an appreciable degree, his ability to operate his car in the manner that an ordinarily prudent and cautious man, in the full possession of his faculties, using reasonable care, would operate … under like conditions.”

• Stanfield v. State, 576 P.2d 772 (Okla. Crim. App. 1978); Bernhardt v. State, 719 P.2d 832 (Okla. Crim. App. 1986); Slusher v. State, 814 P.2d 504 (Okla. Crim. App. 1991); Stewart v. State, 372 P.3d 508 (Okla. Crim. App. 2016) – these decisions reaffirm and apply the Luellen definition across various DUI contexts, including DUI-drugs. Stewart, notably, applies this “under the influence” definition to a statute that, like § 11-902(A)(5), concerns non-alcohol intoxicants.

The Tenth Circuit emphasizes that these Oklahoma cases, together with the Oklahoma Uniform Jury Instructions (OUJI-CR 6-35 and 6-18), establish a stable and clear definition: mere ingestion of an intoxicating substance does not make a driver “under the influence”; the substances must have actually impaired the driver’s ability to operate the vehicle safely to an appreciable degree.

The government argued that because Oklahoma’s uniform instruction for this specific combined-influence offense (OUJI-CR 6-19) does not itself repeat the “under the influence” definition language, the definition was not clearly required here. The panel rejected that argument as formalistic and instead treated the term “under the influence” as a term of art that carries the same definition throughout the state’s DUI scheme, including in Kirby’s offense.

4. The Court’s Legal Reasoning

(a) Standard of review and the abuse of discretion analysis

The court reviewed the district court’s handling of the jury question for abuse of discretion, consistent with Tenth Circuit precedent on jury instructions:

• The court abuses its discretion where its decision rests on an “error of law,” a “clearly erroneous finding of fact,” or “manifests a clear error in judgment.” (Clay, 148 F.4th 1181, 1190 (10th Cir. 2025)).
• That standard applies equally to instructions given before deliberations and responses to jury questions after the jury retires (Zimmerman).

The panel applied that framework in two steps:

1. Was the jury obviously and reasonably uncertain about a central legal rule?
   Yes. The note explicitly asked whether “under the influence” is satisfied by the mere presence of substances in Kirby’s system or requires actual impairment. This went directly to an element of the Oklahoma DUI offense underlying the federal manslaughter count.
2. Was there a clear legal answer the court could have given?
   Yes. Oklahoma law (through decades of cases and uniform instructions) clearly answers that “under the influence” demands proof of impairment rendering the driver incapable (to an appreciable degree) of safely operating a motor vehicle. The court could have supplied that definition or substantially equivalent language.

Given those two premises, directing the jury simply to “revisit” the same ambiguous wording that had sparked confusion in the first place was, in the panel’s view, a “clear error in judgment,” and therefore an abuse of discretion under Bollenbach, Zimmerman, and Duran.

(b) Why the existing instructions were insufficient

The government argued that the original instructions, read as a whole, implicitly required impairment, and that jurors could infer the correct rule from:

• The term “under the combined influence”;
• The phrase “intoxicating substance”;
• The clause “which may render such person incapable of safely driving”; and
• A separate sentence indicating that the blood test could be considered “as to the issue of whether the Defendant’s ability to drive a motor vehicle was impaired.”

The panel rejected these arguments, focusing on textual and practical reasoning:

• Ambiguity of the statutory clause. Grammatically, the “which may render” clause could be read as modifying:
  • only “any other intoxicating substance,” or
  • the entire phrase “under the combined influence of alcohol and any other intoxicating substance.”
  In either case, the clause speaks in terms of what the substances “may” do in general, not what they in fact did to Kirby.
• Mere presence vs. actual effect. Even if “intoxicating” and “influence” imply an ability to affect a person, they do not resolve the jury’s central question: must the jury find those substances actually did impair this defendant’s ability to drive safely on this occasion? Oklahoma law answers “yes”; the raw statutory language does not answer the question “with concrete accuracy.”
• “Clues” in unrelated portions of the instructions are insufficient. The sentence about the blood test bearing on the “issue” of impairment appears in a paragraph addressing only how to treat chemical test results. The panel held this kind of indirect “clue” buried in an instruction is not an adequate substitute when the jury has asked, directly, what the element means. “Jury instructions aren’t a puzzle for jurors to solve,” the court wrote; jurors “are not like pigs, hunting for truffles” in the legal language.

In effect, the court held that the instructions, while tracking the statutory language, were ambiguous in the precise way the jury identified, and thus inadequate to resolve the jurors’ clearly articulated dilemma.

(c) State-law definitions and the federal court’s role

The government tried to minimize the force of Oklahoma cases by relying on United States v. Sain, 795 F.2d 888 (10th Cir. 1986), which said state interpretations of assimilated statutes may have “minimal weight” in federal prosecutions. The panel distinguished Sain:

• Sain concerned “specific provisions of state law” that go beyond “elements of an offense and the range of punishment.”
• In contrast, the meaning of “under the influence” is a substantive element definition, precisely the type of state-law guidance that § 1153(b) requires federal courts to adopt when employing state offenses as predicates.

Thus, the Tenth Circuit treated the Oklahoma definition as controlling for purposes of determining what the government had to prove and what the jury had to be told about the element’s meaning.

(d) Harmless-error analysis

The court did not decide whether the error was constitutional in nature (e.g., misinstruction on an element implicating the Sixth Amendment right to a jury determination of each element), because it found the government could not meet even the lower, nonconstitutional harmless-error standard.

Under that standard, the government had to show by a preponderance of the evidence that the error did not substantially influence the verdict and did not leave the appellate court with “grave doubt” about whether it did. The panel’s reasoning:

• Everyone agreed Kirby had intoxicants in his system. If the jury believed mere presence was enough, it could have convicted without sending a question.
• The jury’s note signals doubt about impairment. At least one juror, and likely more, actively questioned whether Kirby was actually impaired, not just “positive” for substances. Otherwise, the question was unnecessary.
• The evidence of impairment was equivocal.
  • Low BAC;
  • Expert could not opine that Kirby was impaired; and
  • Witness testimony that he seemed sober when leaving the bar.
  At the same time, there were observations consistent with intoxication, creating a disputed factual issue for the jury.
• The timing suggests the legal answer, not a factual re-evaluation, drove the verdict. After the court refused to clarify and told jurors they had all the instructions they needed, they returned a guilty verdict within minutes. The panel drew on Bollenbach, which treated a similar timeline (long deliberations, then swift verdict after confusing supplemental instruction) as strong evidence that the jurors relied on the last word from the judge to break their deadlock.
• The rejection of the alternate theory supports the conclusion that jurors did not find Kirby dangerously incapable of driving safely. The jury unanimously acquitted Kirby on the “lawful act in an unlawful manner” theory—another way of expressing that they were not convinced his driving behavior, apart from intoxication, was grossly negligent or unsafe. This further suggests that if jurors had believed he was clearly incapable of safe driving due to intoxication, they would likely have embraced that theory as well.

The court concluded it had “strong” reason to believe the jury may have convicted under an incorrect legal standard—that mere presence of intoxicants satisfied “under the influence”—and that the government could not show otherwise. Accordingly, the error was not harmless and required vacatur of the conviction.

(e) The concurring opinion’s refinement

Judge Rossman’s concurrence underscores an important limiting principle to the majority’s holding:

• Generally, district courts may answer a jury’s question by referring it back to existing instructions; this is often appropriate and within their discretion.
• An abuse of discretion arises in more “limited circumstances,” such as where:
  • The jury’s confusion concerns a central issue in the case;
  • There is a clear, correct legal answer not already provided by the instructions; and
  • The instructions themselves, though not legally erroneous, do not resolve that confusion.
• She stresses the dual risks a trial judge must balance:
  • Failing to resolve genuine confusion (risking an unjust conviction), and
  • Introducing new error or over-emphasizing one instruction (risking distortion of the charge as a whole).

This concurrence is aimed at preventing an over-reading of Kirby as requiring affirmative supplemental instructions in response to every jury question. It preserves substantial discretion for trial judges while acknowledging that, in the unusual constellation of facts here, more was required.

5. Impact and Future Implications

(a) Strengthening the duty to respond to jury confusion on elements

Kirby cements and slightly elaborates the Tenth Circuit’s “Bollenbach–Zimmerman–Duran” line of cases:

• When a deliberating jury clearly identifies its misunderstanding of a core element of the offense,
• And when that element has a clear doctrinal content (here, supplied by state case law and pattern instructions),
• The district court must offer a concrete and accurate clarification rather than simply re-directing jurors to the original instructions.

Trial judges in the Tenth Circuit will likely feel more pressure—especially in federal prosecutions incorporating state-law elements—to:

• Identify early which elements are terms of art under state law, and
• Build those definitions into the initial instructions, particularly where ambiguity is foreseeable.

If they do not, and ambiguity surfaces during deliberations, Kirby makes clear that refusing to clarify, when a clear answer is available, risks reversal.

(b) Clarification of “under the influence” in Oklahoma-based federal prosecutions

Kirby has immediate practical consequences for prosecutions arising in Oklahoma (and by analogy, elsewhere in the Tenth Circuit where state DUI law is incorporated):

• Federal prosecutors cannot treat the mere presence of intoxicants in a defendant’s system as sufficient for a DUI-based predicate offense; they must prove, and the jury must be told, that the substances actually rendered the defendant incapable of safely operating the vehicle, in line with Luellen and its progeny.
• Evidence of blood levels or positive drug tests, standing alone, is not enough; the government must present circumstantial or expert evidence linking those levels to appreciable impairment at the time of driving.
• Defense counsel will rightly insist on a formal “under the influence” definition where DUI statutes are implicated in federal court—especially in Indian Country prosecutions under § 1153.

(c) Federal courts’ use of state-law definitions under § 1153

Kirby also reinforces that when federal law incorporates state offenses as predicates (as it does under 18 U.S.C. § 1153), federal courts:

• Must look to state law not just for labels and penalty ranges, but also for the substantive contours of the offense elements; and
• Should attend to state high-court precedent and uniform jury instructions in defining those elements for juries.

While Sain cautions that certain state procedural or penalty provisions may not bind federal courts, Kirby clarifies that element definitions—like “under the influence”—are indeed the kind of substantive content federal courts must respect.

(d) Harmless-error doctrine and jury-note cases

Kirby’s harmless-error discussion will likely be cited in future appeals involving:

• Juror notes that reveal confusion about an element,
• Followed by a minimal or nonresponsive judicial reply, and
• A swift verdict thereafter.

The opinion demonstrates the kind of circumstantial inference appellate courts are willing to make:

• Jury sends a note → suggests deadlock or serious doubt.
• Judge’s response does not answer the legal question → does not resolve doubt.
• Quick verdict after response → suggests the jury resolved the case by adopting what they (perhaps incorrectly) understood the law to be, not by re-evaluating the evidence.

In combination with Bollenbach, Kirby endorses the view that such a pattern can make it difficult for the government to prove harmlessness, especially where the underlying evidence is not overwhelming.

(e) Trial-management guidance: what Kirby does not require

Both the majority and the concurrence implicitly signal what Kirby does not hold:

• It does not require judges to answer every jury question with a new instruction; many questions are properly answered by referring the jury back to existing, clear, and complete instructions.
• It does not require judges to craft novel legal glosses where the law itself is open-textured or context-dependent (as in Ness’s “on or about” issue).
• It does not endorse defense counsel’s exact proposed wording as mandatory; rather, it insists that the substance of the state-law definition—actual impairment of safe driving ability—must be conveyed.

Thus, Kirby is best read as a strong case applying a previously existing principle to unusually clear facts, not as a wholesale reworking of the law of supplemental jury instructions.

Complex Concepts Simplified

1. “Under the Influence” versus “Mere Ingestion”

In everyday terms:

• Mere ingestion means: a person drank alcohol or took a drug, and it shows up in a blood test.
• Under the influence (as defined by Oklahoma law) means: the alcohol/drug has actually affected the person’s brain, nerves, or muscles enough that their ability to drive like a careful, sober driver is noticeably worse.

Thus, someone might:

• Have a low BAC (like 0.028) or a small dose of a prescribed drug → substance is in their system, but
• Still be able to drive safely → not “under the influence” for DUI purposes.

2. “Abuse of Discretion”

Appellate courts often review a trial judge’s day-to-day decisions under a forgiving standard called “abuse of discretion.” It means:

• The appellate court does not ask what it would have done, but whether the trial judge’s decision:
  • Was based on the wrong law, or
  • Rested on clearly wrong facts, or
  • Was so unreasonable that it reflected a serious error in judgment.

In Kirby, the panel concluded that, given the clarity of Oklahoma law and the clarity of the jury’s question, refusing to answer and sending them back to the same ambiguous language was such an error in judgment.

3. Harmless Error (Nonconstitutional)

Even when a trial judge makes a mistake, an appellate court will not automatically reverse. For nonconstitutional errors, the question is:

• Is it more likely than not that the error did not affect the outcome?

If the government cannot show this (i.e., the appellate judges have “grave doubt” whether the error mattered), the conviction must be reversed. Kirby illustrates this: because the jury’s note, the timing of the verdict, and the equivocal evidence all suggest the legal misunderstanding likely drove the outcome, the error could not be deemed harmless.

4. Involuntary Manslaughter “in Indian Country”

“In Indian Country” is a jurisdictional term under federal law. When certain serious crimes occur in Indian Country and involve Native American defendants (or victims), federal courts have jurisdiction under 18 U.S.C. § 1153. Here:

• Kirby is a tribal member;
• The crash occurred within Indian Country in Oklahoma;
• Thus, the United States prosecuted involuntary manslaughter in federal court, relying on an Oklahoma DUI misdemeanor as the underlying “unlawful act not amounting to a felony” under § 1112.

5. Jury Instructions and Supplemental Instructions

A “jury instruction” is the judge’s explanation of the law the jury must apply to the facts. A “supplemental instruction” is a later explanation or clarification given after the jury begins deliberating, typically in response to a question.

Key points from Kirby about supplemental instructions:

• If the jury’s question shows confusion about a central legal point, and a clear answer exists, the court should answer directly, not just point back to ambiguous language.
• If the law is inherently vague or context-specific, the court may be justified in repeating the standard formulation without “narrowing” it further (as in Ness).

Conclusion

United States v. Kirby is a significant reaffirmation of a core trial principle: when jurors explicitly ask what an element of the offense means, and the law provides a clear answer, the court must give that answer, not leave jurors to guess. In the context of Indian Country manslaughter prosecutions premised on state DUI law, the case makes clear that “under the influence” in Oklahoma means actual, appreciable impairment of safe-driving ability—not merely having alcohol or drugs in one’s bloodstream.

Doctrinally, Kirby strengthens the Tenth Circuit’s jurisprudence on responding to jury questions, emphasizes the binding role of state substantive law in defining elements under § 1153, and illustrates how harmless-error analysis operates when a jury’s note and timing strongly suggest that a misunderstood legal standard drove the verdict.

For practitioners, Kirby is both a warning and a guide:

• Trial courts should identify and define state-law terms of art—especially in assimilated or incorporated offenses—up front, and must be prepared to clarify them if a jury later asks.
• Prosecutors may need to marshal stronger proof of actual impairment in DUI-based manslaughter cases and ensure the jury understands that element.
• Defense counsel now have solid precedent to challenge convictions where juries clearly struggled with element definitions and received no meaningful guidance.

Above all, Kirby underscores that justice in jury trials depends not only on accurate abstract legal statements but on timely, concrete answers to jurors’ real-world questions about what the law actually requires them to find.