Rule 16(a)(1)(G) Rebuttal Disclosures Are Limited to Countering Timely-Disclosed Defense Expert Opinions

1. Introduction

United States v. Crow addresses a recurring trial-management problem after the 2022 amendment to Federal Rule of Criminal Procedure 16: when, if ever, must the government provide pretrial notice of expert rebuttal opinions that arise only because a defense expert offers new, previously undisclosed opinions during trial?

The prosecution charged Mitchel Crow with sexual abuse of a minor under 18 U.S.C. § 2243(a) based on sexual acts occurring at a military base. The sexual conduct itself was undisputed (Crow admitted having sex), but the case turned on state of mind—whether Crow was awake and acting knowingly, or asleep and acting under “sexsomnia.” The parties presented competing experts: Dr. Clete Kushida for the defense and Dr. Michel A. Cramer Bornemann for the government.

The core appellate issue was procedural: whether the government violated Rule 16 by presenting rebuttal expert opinions at trial (about “malingering”) without having disclosed those opinions sufficiently in advance to allow meaningful preparation and cross-examination.

2. Summary of the Opinion

The court reasoned that amended Rule 16 ties the government’s rebuttal-disclosure duty to rebuttal “to counter testimony that the defendant has timely disclosed.” Here, the defense expert’s trial testimony expanded into new opinions on malingering and truthfulness that were not contained in his report. Because the defense had not timely disclosed those opinions, the government’s rebuttal to them did not trigger a pretrial disclosure duty under Rule 16(a)(1)(G)(i).

The court also rejected an attempt—raised only in the reply brief—to obtain reversal based on “unfairness” independent of Rule 16. That argument was deemed waived.

3. Analysis

3.1 Precedents Cited

United States v. Freeman

The panel cited United States v. Freeman, 70 F.4th 1265, 1286 (10th Cir. 2023), for the standard of review: interpretation of the Federal Rules of Criminal Procedure is reviewed de novo. This mattered because the appeal turned primarily on the meaning and triggering conditions of Rule 16(a)(1)(G)(i), not on discretionary trial management alone.

United States v. Frazier

The court cited United States v. Frazier, 387 F.3d 1244, 1269 (11th Cir. 2004), to explain the pre-2022 baseline: historically, Rule 16’s expert-disclosure obligation applied to the government’s case-in-chief, not rebuttal. That historical framing supported the court’s careful reading of the 2022 amendment as limited—a new rebuttal duty, but only within defined conditions.

Greenlaw v. United States

The panel invoked Greenlaw v. United States, 554 U.S. 237, 243 (2008), for the “principle of party presentation”: appellate courts generally rely on the parties to frame the issues. That principle underwrote the court’s decision to assume without deciding that the 2022 Rule 16 amendment applied to this case, because the district court and parties had not developed the “just and practicable” question for applying amendments to pending cases.

United States v. Leffler

The court relied on United States v. Leffler, 942 F.3d 1192, 1197-98 (10th Cir. 2019), to reject a late-shifted theory: Crow argued in his reply brief that reversal was warranted even absent a Rule 16 violation because the district court was unfair in limiting interview time. Under Leffler, that argument was waived because it was not raised in the opening brief as an independent ground for reversal.

3.2 Legal Reasoning

(a) The court’s framing of the triggering condition in amended Rule 16

The opinion turns on the amended text: Rule 16(a)(1)(G)(i) requires disclosure in writing of rebuttal expert testimony “to counter testimony that the defendant has timely disclosed under (b)(1)(C).” The panel treated this as a threshold requirement: the government’s rebuttal duty is not free-standing; it is conditional on the defense’s timely disclosure of the opinions being rebutted.

(b) The factual hinge: what the defense expert disclosed vs. what he actually testified to

The court drew a sharp line between:

• Disclosed opinion (pretrial): Dr. Kushida’s report opined that Crow’s actions “could have been the result of” sexsomnia / NREM parasomnias, and discussed consistency with sleep-related abnormal behavior.
• New opinion (at trial): Dr. Kushida went further into malingering and effectively offered an opinion bearing on Crow’s truthfulness—i.e., that he did not believe Crow was malingering in pursuit of a sexsomnia diagnosis.

The government’s expert, Dr. Bornemann, then offered new rebuttal opinions addressing that malingering-related testimony. Because the defense did not “timely disclose” malingering opinions, the court held the government was not required—under Rule 16(a)(1)(G)(i)—to pre-disclose rebuttal to them.

(c) Rejection of the “opened the door”/cross-examination justification

Crow argued that malingering was elicited only to rehabilitate the defense expert after cross-examination about “secondary gain.” The panel distinguished secondary gain (incentive) from malingering (feigning symptoms / untruthfulness): conceding an incentive is not the same as opining that the defendant is or is not lying. On the court’s view, the defense introduced the first explicit malingering/truthfulness opinion at trial—beyond what had been disclosed—so Rule 16’s rebuttal-disclosure trigger still was not satisfied.

(d) The court’s “assume applicability” move and its practical effect

Rule amendments applied to cases “thereafter commenced,” but could be applied to pending cases “insofar as just and practicable.” The Tenth Circuit did not decide that question; it assumed the amendment applied and still found no Rule 16 violation. Practically, that approach insulated the judgment from the transitional-amendment issue and produced a rule that applies cleanly even in post-2022 prosecutions: rebuttal disclosure is keyed to what the defense actually disclosed.

(e) The limited scope of the decision

The court emphasized that the appeal was anchored to Rule 16(a)(1)(G)(i). Although the parties later discussed supplementation (Rule 16(c)) in briefing, the court did not reach it, because Crow “relied only on Rule 16(a)(1)(G)(i).” Thus, Crow is best read as a decision about the trigger for rebuttal disclosure, not a complete map of the government’s supplementation obligations.

3.3 Impact

• Defense disclosure discipline: The decision creates strong incentives for defense teams to ensure expert reports and Rule 16(b)(1)(C) disclosures encompass any opinions reasonably expected at trial—especially opinions that could open new rebuttal lines (e.g., malingering, credibility-adjacent assessments, diagnostic validity).
• Constraining “surprise rebuttal” claims: Post-2022, defendants may be tempted to argue that the new rebuttal-disclosure duty broadly prohibits surprise rebuttal. Crow narrows that: the duty runs only to rebuttal of timely-disclosed defense opinions.
• Trial-court management remains important but must be preserved: The panel’s waiver holding signals that “unfairness/time-to-interview” arguments must be raised as independent appellate issues from the outset, not saved for a reply brief.
• Potential future litigation on Rule 16(c): Because the court did not reach supplementation, future cases may test whether and when Rule 16(c) requires updating disclosures for evolving rebuttal opinions even when the defense opinion was not “timely disclosed.”

4. Complex Concepts Simplified

• Rebuttal evidence: Evidence presented after the opposing party’s case to respond to or “counter” what the opponent presented. Here, the government used rebuttal expert testimony to respond to defense expert testimony.
• Rule 16(a)(1)(G)(i) (2022 amendment): Requires the government, upon request, to provide written summaries of expert testimony it intends to use in its case-in-chief and in rebuttal—but rebuttal disclosure is limited to testimony countering “timely disclosed” defense expert testimony.
• “Timely disclosed”: Disclosed within the deadlines and scope required by Rule 16(b)(1)(C) and any scheduling orders—meaning not merely “mentioned at trial,” but actually provided in pretrial disclosure materials.
• Malingering: Feigning or exaggerating symptoms for external gain. In this case, it was tied to whether Crow might falsely claim a sleep disorder to avoid culpability.
• Sexsomnia / parasomnia: A sleep-related disorder in which a person may engage in sexual behavior while asleep; “parasomnia” is a broader category of abnormal behaviors during sleep.
• De novo review: The appellate court decides the legal question anew, without deferring to the district court’s interpretation.
• Waiver vs. forfeiture (as used here): The court treated the late-raised “unfairness” claim as waived because it was not raised in the opening brief; separately, it rejected the government’s claim that Crow forfeited the Rule 16 argument because trial objections preserved timing/substance concerns.
• Nunc pro tunc correction: A clerical correction reissued effective as of the original filing date; it does not change the substantive legal rule announced.

5. Conclusion

United States v. Crow establishes a clear limiting principle for the 2022 amended Rule 16 expert rebuttal-disclosure requirement in the Tenth Circuit: the government’s pretrial rebuttal disclosure duty is triggered only when rebuttal will counter defense expert opinions that were themselves timely disclosed. When a defense expert expands into new territory at trial—here, malingering/truthfulness—the government may rebut without having provided pretrial notice of rebuttal opinions aimed at that undisclosed testimony.

The decision also underscores an appellate practice point: if a defendant seeks reversal on fairness or trial-management grounds independent of Rule 16, that theory must be developed in the opening brief—or it risks waiver under United States v. Leffler.