United States v. Rivera: Tenth Circuit Endorses “Blind” Grooming-Expert Testimony and Clarifies Rule 702/703 Reliance on Third-Party Technical Data

I. Introduction

In United States v. Rivera (10th Cir. 2025) the Court of Appeals addressed a constellation of evidentiary objections raised by a defendant convicted of sexually exploiting a 12-year-old. Although the judgment is designated “non-precedential,” the panel’s careful discussion carries persuasive force on four recurring trial issues:

Admission of “blind” law-enforcement experts who testify about the generic phenomenon of child-sex-offender grooming without knowing the facts of the particular case.
Scope of an expert’s permissible reliance, under Rules 702 and 703, on information obtained after the Daubert hearing—here, a telephone call with a Verizon technician about automatic file conversion.
Application of Rule 414 and the Enjady factors to admit the victim’s testimony about uncharged, prior sexual abuse by the same defendant.
Limits imposed by Rules 608(b) and 403 on defense efforts to impeach a minor victim with specific acts of dishonesty unrelated to the charged conduct.

By affirming the district court on every point, the Tenth Circuit furnishes a practical template for trial judges and litigants confronting similar evidentiary battles in child-exploitation prosecutions.

II. Summary of the Judgment

Rivera, an adult, was convicted in the District of New Mexico of (1) coercion and enticement of a minor (18 U.S.C. § 2422(b)) and (2) two counts of producing child pornography (18 U.S.C. § 2251). On appeal he raised four primary claims:

Rule 702 error in admitting FBI Supervisory Special Agent Daniel O’Donnell’s “blind” grooming testimony.
Rule 702/703 (and Confrontation Clause) error concerning FBI Special Agent Sean Macmanus’s testimony that Verizon’s network can convert MP4 videos to 3GPP format without altering content.
Error in admitting, under Rule 414 (and Rule 404(b)), the victim’s account of an earlier sexual assault by Rivera.
Error in excluding defense impeachment evidence that the victim once lied about her age to a traffic officer.

Applying abuse-of-discretion review for the evidentiary rulings and plain-error review for the forfeited Confrontation claim, the panel (Holmes, C.J., Carson & Rossman, JJ.) affirmed across the board, emphasizing the district court’s robust Daubert gate-keeping, explicit Rule 403 balancing, and curative limiting instructions.

III. Analysis

A. Precedents Cited and Their Influence

Daubert v. Merrell Dow Pharm., 509 U.S. 579 (1993) – Grounded the district court’s gate-keeping inquiry for both experts.
United States v. Enjady, 134 F.3d 1427 (10th Cir. 1998) – Provided the six-factor framework (four probative, three prejudice) for Rule 403 balancing of Rule 414 evidence.
United States v. Rodriguez-Felix, 450 F.3d 1117 (10th Cir. 2006) and United States v. Nacchio, 555 F.3d 1234 (10th Cir. 2009) – Articulated standards of review for Daubert decisions.
United States v. Gutierrez de Lopez, 761 F.3d 1123 (10th Cir. 2014) – Cited for Confrontation Clause review methodology.
United States v. Piette, 45 F.4th 1142 (10th Cir. 2022) and United States v. Harjo, 122 F.4th 1240 (10th Cir. 2024) – Recent Tenth Circuit writing on Rule 414 that the panel followed.

B. The Court’s Legal Reasoning

1. “Blind” Grooming-Expert Testimony

Rivera argued that Agent O’Donnell’s generalized testimony, uninformed by any case-specific facts, lacked a reliable methodology. The panel rejected this, stressing:

The Advisory Committee notes expressly contemplate experts who “educate the factfinder about general principles” without applying them to the case facts.
Agent O’Donnell’s five-stage grooming model is anchored in peer-reviewed social-science literature (no rebuttal evidence questioned its acceptance).
The risk of “vouching” was minimal because the expert had no knowledge of the victim or investigation.

Key take-away: A law-enforcement professional may provide “blind”, background testimony on grooming so long as the model is grounded in accepted literature and the district court performs an on-record Rule 702/403 analysis.

2. Expert Reliance on Post-Daubert Information (Rules 702 & 703)

Agent Macmanus, initially qualified as a cellular-records expert, later confirmed with a Verizon technician that large MP4 files can be automatically down-converted to 3GPP by Verizon’s MMS servers. Rivera said this showed Macmanus lacked the expertise himself and deprived the defense of confrontation rights. The Tenth Circuit held:

Rule 703 expressly permits experts to base opinions on data “made aware of” them, including hearsay, if experts reasonably rely on such data in the field.
Macmanus’s specialized training (cyber-security certificates, prior courses by Verizon and Facebook) provided an independent expert foundation; the Verizon call merely confirmed his view.
No Confrontation Clause violation occurred because the Verizon employee’s statements were not offered for their truth independently; they were background “facts or data” under Rule 703, and Rivera failed to lodge a constitutional objection below or establish plain error.

3. Prior Sexual Assault Evidence under Rule 414

The panel endorsed the district court’s meticulous Enjady balancing:

Proof Strength: Victim’s testimony sufficed under the preponderance standard—no corroboration is required.
Probative Value: The 2021 hands-on assault explained the trust relationship and why the victim later complied with Rivera’s sexting demands.
Dispute Seriousness: Identity and nature of the relationship were vigorously contested.
No Less Prejudicial Alternative: Only the victim could supply the narrative context.
Prejudice Factors: Limiting instructions curbed propensity misuse; the testimony was brief; and the issues were not likely to confuse jurors.

The court thus found the evidence “highly probative” and not unfairly prejudicial—a textbook application of Rule 414.

4. Impeachment of the Victim (Rules 608(b) & 403)

Rivera wanted to show the jury a cruiser video in which the 12-year-old lied about her age during an unrelated traffic stop. Under Rule 608(b) extrinsic proof of specific conduct is inadmissible, and even cross-examination questions rest on the trial court’s Rule 403 discretion. The panel upheld exclusion because:

The lie was a “garden-variety juvenile falsehood” with scant probative value on truthfulness regarding sexual accusations.
The risk of unfair prejudice and juror distraction was substantial.
Trial courts enjoy broad latitude in managing peripheral impeachment.

C. Impact of the Judgment

Solidifies acceptance of “blind” grooming experts in the Tenth Circuit, lowering prosecutorial burdens when the expert simply educates the jury on grooming dynamics.
Expands practical use of Rule 703 for technical experts who corroborate opinions with informal consultations—courts are unlikely to require live confrontation with every behind-the-scenes technician.
Confirms that hands-on abuse and child-porn production are sufficiently related to be mutually admissible under Rule 414.
Reaffirms narrow impeachment windows for juvenile witnesses; trial courts may exclude low-probative dishonesty evidence to prevent “mini-trials” on collateral matters.

IV. Complex Concepts Simplified

1. “Blind” Expert

A blind expert testifies to general principles without learning case-specific facts. This avoids any appearance of having coached the victim or tailored opinions, reducing vouching concerns. The trade-off is that the expert cannot apply those principles to the facts in controversy; the jury must do so.

2. Rule 702 vs. Rule 703

Rule 702 governs admissibility of the opinion itself—the expert must be qualified, and the opinion must be reliable and helpful.
Rule 703 governs the sources the expert may consult—even inadmissible hearsay—so long as experts in that field would reasonably rely on it.

3. Automatic File Conversion (MP4 → 3GPP)

Large video files sent via MMS often exceed carrier size limits; Verizon’s servers transcode such files to 3GPP (smaller, lower resolution) before delivery. The content remains substantively identical—only the wrapper/codec changes.

4. Rule 414 and the Enjady Factors

Unlike Rule 404(b), Rule 414 expressly authorizes courts to admit a defendant’s other child-molestation acts to show propensity. Yet, courts must still apply Rule 403 through the six Enjady sub-factors to ensure fairness and proportionality.

5. Rule 608(b) Limitations

Parties may ask a witness about specific dishonest acts, but they must accept the witness’s answer; no documents, videos, or other extrinsic proof can be introduced. Judges routinely exclude marginal impeachment to prevent juror confusion.

V. Conclusion

Although unpublished, United States v. Rivera supplies a highly instructive roadmap for federal trial courts navigating expert admissibility, Rule 414 propensity evidence, and witness impeachment in child exploitation cases. Key lessons include:

Generalized grooming science—delivered by a blind, law-enforcement expert— comfortably satisfies Rule 702 when the district court articulates its reliability findings.
Experts may buttress opinions with later-acquired hearsay so long as that method is standard in the field and disclosed to opposing counsel.
Hands-on molestation and digital exploitation are logically intertwined; Rule 414 reaches both.
Collateral acts of juvenile dishonesty are weak impeachment and face steep Rule 403 headwinds.

For prosecutors, the opinion validates strategic use of educational experts and Rule 414 evidence; for defense counsel, it signals the need for early, focused Daubert challenges and plain-error preservation; and for trial judges, it underscores the importance of building a detailed evidentiary record that can survive deferential appellate review.