“Overwhelming Evidence” and the Harmless-Error Shield:
United States v. Belas Rosier, No. 23-14234 (11th Cir. July 2, 2025)

Introduction

United States v. Belas Rosier is an unpublished Eleventh Circuit opinion that nevertheless furnishes a useful road map for two recurring criminal-procedure controversies: (1) the admissibility of expert “code-word” testimony that arguably speaks to the defendant’s mental state in violation of Federal Rule of Evidence 704(b); and (2) the scope of appellate review for substantive reasonableness of within-Guidelines sentences.

Rosier was convicted in the Southern District of Florida of one count of conspiracy to possess with intent to distribute mixtures containing large quantities of fentanyl and cocaine, and one count of possession with intent to distribute those substances. On appeal he argued (i) that Detective Negron’s expert testimony impermissibly interpreted text-message “code words” and opined on Rosier’s intent, and (ii) that his 180-month sentence was substantively unreasonable because the district court over-emphasised drug quantity. The Eleventh Circuit affirmed, holding that any Rule 704(b) violation was harmless beyond a reasonable doubt, and that the sentence was well within the district court’s discretion under 18 U.S.C. § 3553(a).

Summary of the Judgment

• Expert Testimony Issue. The panel assumed, without deciding, that Detective Negron’s testimony could have crossed the Rule 704(b) line, but ruled the admission harmless because of “overwhelming evidence of guilt.”
• Sentencing Issue. The 180-month sentence fell in the middle of the 151-to-188-month Guidelines range and was adequately explained; the court therefore found no abuse of discretion.
• Disposition. Conviction and sentence affirmed.

Analysis

1. Precedents Cited

1. United States v. Pon, 963 F.3d 1207 (11th Cir. 2020) – clarified harmless-error review for preserved errors.
2. United States v. Olano, 507 U.S. 725 (1993) – foundational harmless-error framework distinguishing constitutional from non-constitutional errors.
3. Gall v. United States, 552 U.S. 38 (2007) – abuse-of-discretion standard for sentencing.
4. Rita v. United States, 551 U.S. 338 (2007) – presumption that within-Guidelines sentences are reasonable when adequately explained.
5. United States v. Irey, 612 F.3d 1160 (11th Cir. 2010) – clarifies when a court commits a “clear error of judgment” in weighing § 3553(a) factors.
6. Other Eleventh Circuit cases – Castaneda, Kuhlman, Shaw, Grushko, Gonzalez, and Alberts – each reinforcing either harmless error or sentencing-reasonableness doctrines.

By invoking these authorities, the panel re-situated Rosier’s complaints within well-trodden jurisprudential lines: harmlessness under Olano and sentencing review under Gall/Rita.

2. Legal Reasoning

2.1 The Rule 704(b) / Code-Word Testimony Question

Rule 704(b) bars experts from stating “an opinion or inference as to whether the defendant did or did not have the mental state…that constitutes an element of the crime.” Detective Negron identified drug-slang meanings (“4” = four ounces of fentanyl; “9” = nine ounces, etc.) and repeatedly asserted that Rosier was the sender. Rosier argued this impermissibly conveyed that he knowingly conspired.

The Eleventh Circuit sidestepped the admissibility question and proceeded directly to harmless-error analysis. Applying the constitutional harmless-error standard, the panel asked whether the government proved “beyond a reasonable doubt” that the admission “did not contribute to the verdict.” In support it catalogued:

• 1,250 calls/texts linking the “Bizly” phone (registered to Rosier, sharing his birthday, linked to his residence) with known dealer Justin Garth;
• 524 g fentanyl, 43.99 g fentanyl analogue, and 286 g cocaine recovered from Rosier’s home;
• Numerous text strings whose drug-trafficking content was self-evident even without expert gloss.

Given this “overwhelming evidence,” the court concluded Negron’s opinions were “unimportant in relation to everything else.” This echoes Pon, where improper testimony was deemed harmless because of independent proof.

2.2 Substantive Reasonableness of the Sentence

Rosier’s Guidelines range was 151–188 months; the district court selected 180 months. Appellate review asks whether the court: (1) considered the § 3553(a) factors, and (2) abused its discretion by placing too much or too little weight on any factor.

The panel highlighted that the district court:

• Expressly said it had considered all § 3553(a) factors and the parties’ arguments;
• Focused on the “truly staggering” drug quantity, the “degree of sophistication,” proximity to “minor children,” and the need for general deterrence of fentanyl trafficking;
• Chose a term within the Guidelines range, creating a presumption of reasonableness under Rita.

Hence no “clear error of judgment” occurred.

3. Potential Impact

• Practical Guidance on Harmless Error. The opinion underscores that—even where expert testimony flirts with Rule 704(b)—a conviction will survive if the independent evidence is overwhelming. Defendants should therefore develop a thorough trial record challenging each piece of corroborating evidence, not merely the expert gloss.
• Strategic Significance for the Government. Prosecutors may view the case as an assurance that introducing code-word experts, though risky, will rarely trigger reversal if ample corroborative proof exists.
• Sentencing Advocacy. Defense counsel should recognize that within-range sentences remain “ordinarily” reasonable; meaningful appellate relief will require showing the district court ignored key mitigating data, relied on impermissible facts, or issued a guideline-range sentence that is “shockingly high.”
• Rule 704(b) Litigation. The court’s decision not to reach the merits leaves unresolved the precise line demarcating permissible code-word interpretation from forbidden mental-state opinions. Future appellants may seek to cultivate clearer factual records to obtain a precedential ruling.

Complex Concepts Simplified

Rule 704(b)

Prevents expert witnesses from testifying directly about a defendant’s intent, guilt, or mental state.

Harmless Error (Constitutional vs. Non-constitutional)

Constitutional. Government must show beyond a reasonable doubt the error did not affect the verdict.
Non-constitutional. Government must show there is no reasonable probability the outcome would have changed.

18 U.S.C. § 3553(a) Factors

Statutory considerations guiding federal sentencing: seriousness of the offence, deterrence, protection of the public, defendant’s history, and so forth.

Substantive Reasonableness

An appellate standard asking whether the chosen sentence is too long or too short in light of § 3553(a) factors—different from procedural reasonableness (whether the court followed correct steps).

Guidelines Range

The sentencing range produced by the U.S. Sentencing Guidelines after assigning an offence level and criminal history category.

Conclusion

Although non-precedential, United States v. Belas Rosier captures two recurrent themes in federal criminal appeals. First, even arguable violations of Rule 704(b) will not yield reversal where the government marshals strong corroborating evidence; “overwhelming evidence of guilt” remains the ultimate harmless-error shield. Second, within-Guidelines sentences continue to enjoy an “ordinary” presumption of reasonableness provided the district court articulates a plausible nexus to § 3553(a) factors. Practitioners should therefore view Rosier as a reminder that success on appeal often hinges on the strength of the trial record, not merely on discrete evidentiary or sentencing objections.