1. Introduction

This sentencing appeal arises from a search-warrant execution at the San Juan apartment where Heclouis Joel Nieves-Díaz was residing. Police found, among other items, 149 rounds of .223 ammunition, a machine gun conversion device (“chip”), and approximately 849 small baggies of cocaine. Nieves pleaded guilty to: (1) felon-in-possession of ammunition (18 U.S.C. §§ 922(g)(1), 924(a)(2)), (2) possession of a machine-gun conversion part (18 U.S.C. §§ 922(o), 924(a)(2)), and (3) possession with intent to distribute cocaine (18 U.S.C. § 841(a)(1), (b)(1)(C)).

After an earlier appeal (United States v. Nieves-Díaz (Nieves I), 99 F.4th 1 (1st Cir. 2024)) vacated his first sentence due to an incorrectly applied Guidelines enhancement, the district court resentenced Nieves to 66 months—an upward variance of 25 months above the top of the new Guidelines range (33–41 months). The principal issue on this second appeal was procedural reasonableness: whether the sentencing judge adequately explained and individualized the upward variance, particularly the reliance on the quantity of ammunition where no firearm was found.

2. Summary of the Opinion

The court declined to (a) reach substantive reasonableness, (b) cap the sentence on remand, or (c) reassign the case to a different judge.

3. Analysis

3.1 Precedents Cited (and How They Shaped the Decision)

• United States v. Nieves-Díaz (Nieves I), 99 F.4th 1 (1st Cir. 2024): The prior appeal held the district court erroneously applied U.S.S.G. § 2K2.1(b)(6)(B) (ammo/firearm “in connection with” another felony) because the record did not support that the ammunition potentially facilitated drug trafficking. The panel also cautioned that any upward variance on remand would require a “case-specific explanation” or an explicit “policy disagreement.” In the present decision, the court clarified that Nieves I did not bar an upward variance based on ammunition quantity; it merely rejected the specific enhancement’s factual predicate.
• United States v. Flores-Quiñones, 985 F.3d 128 (1st Cir. 2021) and United States v. Cruz-Ramos, 987 F.3d 27 (1st Cir. 2021): Provided the framework: appellate review proceeds first through procedural reasonableness, and preserved claims are reviewed for abuse of discretion.
• United States v. Pupo, 995 F.3d 23 (1st Cir. 2021) (quoting United States v. Díaz-Rivera, 957 F.3d 20 (1st Cir. 2020)): Anchored the core procedural rule: a sentencing court errs by “failing to adequately explain the chosen sentence—including an explanation for any deviation from the [GSR].”
• United States v. Nelson, 793 F.3d 202 (1st Cir. 2015): Reaffirmed that the variance decision and its extent are “judgment call[s]” reviewed for reasonableness, but only if the explanation allows meaningful review.
• United States v. Mercado-Cañizares, 133 F.4th 173 (1st Cir. 2025): Supplied the proportionality principle the panel applied: the court must clearly identify the ammunition amount as a rationale and ensure the explanation is “commensurate with the magnitude of variance.”
• United States v. Polaco-Hance, 103 F.4th 95 (1st Cir. 2024) and United States v. Gonzalez-Flores, 988 F.3d 100 (1st Cir. 2021): These cases were cited by the district court to justify considering ammunition quantity when the Guidelines do not account for it. The First Circuit agreed ammunition quantity can justify a variance, but held the district court still had to explain why it mattered here—especially given the absence of a firearm.
• United States v. Maldonado-Velazquez, 164 F.4th 154 (1st Cir. 2026) (quoting United States v. Bruno-Campos, 978 F.3d 801 (1st Cir. 2020)): Provided the “heartland” concept: serious firepower and substantial ammunition quantities may remove a case from the Guidelines’ ordinary range of cases.
• Ammunition-quantity variance precedents (all involving firearm possession): United States v. García-Mojica, 955 F.3d 187 (1st Cir. 2020); United States v. Contreras-Delgado, 913 F.3d 232 (1st Cir. 2019); United States v. Morales-Vélez, 100 F.4th 334 (1st Cir. 2024); United States v. Santa-Otero, 843 F.3d 547 (1st Cir. 2016). The panel used these cases to show that prior approvals of ammo-based variances typically rested on either (a) increased dangerousness because the ammunition augmented a weapon’s lethal capacity, (b) sheer quantity, or (c) distinctive features (e.g., loaded magazines). That background underscored what was missing here: an explanation tied to the no-firearm fact pattern.
• United States v. Colón-Cordero, 91 F.4th 41 (1st Cir. 2024) and United States v. Montero-Montero, 817 F.3d 35 (1st Cir. 2016): Colón-Cordero supplied the requirement that a district court engage with a defendant’s “dominant” argument. Montero-Montero supported vacatur where an appellate court cannot discern the sentencing court’s reasoning and should not “guess,” especially with a marked variance.
• Criminal-history and recidivism support: United States v. Bermúdez-Meléndez, 827 F.3d 160 (1st Cir. 2016); United States v. Fargas-Reyes, 125 F.4th 264 (1st Cir. 2025); United States v. Polaco-Hance, 103 F.4th 95 (1st Cir. 2024). These cases supported the panel’s guidance that the district court may, on remand, reasonably rely on Nieves’s history (including supervised-release failures and quick reoffending) as a variance consideration.
• Community factors (gun violence) limits: United States v. Zapata-Vázquez, 778 F.3d 21 (1st Cir. 2015) and United States v. Flores-Machicote, 706 F.3d 16 (1st Cir. 2013): These cases confirm that courts may emphasize community deterrence so long as it does not displace individualized consideration; the court need not find the defendant personally committed community violence to consider deterrence.
• Remand scope / not reaching substantive reasonableness: United States v. Carrasquillo-Sánchez, 9 F.4th 56 (1st Cir. 2021).
• No instruction to impose a specific (or capped) sentence: United States v. Helton, 782 F.3d 148 (4th Cir. 2015); United States v. Mojica-Ramos, 103 F.4th 844 (1st Cir. 2024) (quoting United States v. Kurkculer, 917 F.2d 295 (1st Cir. 1990)); contrasted with the rare cap-imposing scenario in United States v. Rivera-Berríos, 968 F.3d 130 (1st Cir. 2020).
• Reassignment standard: Yosd v. Mukasey, 514 F.3d 74 (1st Cir. 2008) (quoting Liteky v. United States, 510 U.S. 540 (1994)); United States v. Vázquez-Méndez, 915 F.3d 85 (1st Cir. 2019); United States v. Castillo-Torres, 8 F.4th 68 (1st Cir. 2021); United States v. Alvira-Sanchez, 804 F.3d 488 (1st Cir. 2015); and the “typical remand” example United States v. Muñoz-Fontanez, 61 F.4th 212 (1st Cir. 2023). These authorities drove the denial of reassignment absent unreliable information or entrenched bias.

3.2 Legal Reasoning

The First Circuit’s holding is tightly procedural: the district court gave three main reasons for the 25-month upward variance—(i) Nieves’s criminal history/recidivism, (ii) the ammunition quantity, and (iii) Puerto Rico’s gun violence and deterrence needs. Because the record did not indicate the court would have imposed the same sentence without each factor, the panel required enough explanation to review each “ingredient” in the variance “mix.”

The explanation failed at the ammunition step. The sentencing court said the Guidelines did not account for the “amount of ammunition” and cited United States v. Polaco-Hance and United States v. Gonzalez-Flores. But it did not explain what about the 149 rounds mattered in this defendant’s circumstances—especially in light of Nieves’s “principal argument” that he had no firearm and therefore posed less danger.

The panel emphasized that prior ammo-variance cases typically involved a firearm and often linked extra ammunition to enhanced lethality, heightened risk, or features like loaded magazines. Here, “a novel circumstance” required the district court to articulate whether the aggravation came from: potential danger despite no gun, sheer quantity as an indicator of seriousness, linkage to drug trafficking operations, inference of access to weapons, or some other case-specific concern. With a “marked” variance, the appellate court refused to infer the rationale.

Importantly, the panel did not hold that ammo quantity can never justify a variance without a firearm; it held only that, on this record, the sentencing court did not explain its reasoning sufficiently to permit review.

3.3 Impact

• Heightened explanation duty in “no-firearm ammunition” cases: The decision signals that when ammunition quantity is used to justify an upward variance and the defendant credibly argues that the absence of a firearm reduces dangerousness, the sentencing court must address that contention and explain what makes the ammunition aggravating in context.
• Variance magnitude drives explanation detail: Reinforcing United States v. Mercado-Cañizares, the opinion underscores that a large upward variance (here, ~61% above the range’s top) requires an explanation commensurate with that degree of deviation.
• District courts retain discretion—but must build a reviewable record: The First Circuit preserved the possibility of the same sentence on remand, provided the judge explains the ammunition rationale and ties it to individualized § 3553(a) factors.
• Recidivism remains a robust variance basis: By expressly validating reliance on supervised-release history and “speed with which he reoffends,” the opinion strengthens the government’s and probation’s hand in arguing upward variances for rapid reoffending patterns, even when some violations are characterized as “technical.”
• Community deterrence remains permissible but not substitutive: The panel’s discussion (via Polaco-Hance, Zapata-Vázquez, and Flores-Machicote) confirms that Puerto Rico’s gun-violence context can inform deterrence, but must be balanced with the defendant’s specific conduct.

4. Complex Concepts Simplified

• GSR (Guidelines Sentencing Range): The advisory imprisonment range produced by the U.S. Sentencing Guidelines after calculating the offense level and criminal history category (here, 33–41 months at resentencing).
• Upward variance: A sentence above the GSR based on the statutory sentencing factors in 18 U.S.C. § 3553(a), not a Guidelines “departure.” Variances must be explained and individualized.
• Procedural vs. substantive reasonableness: Procedural review asks whether the court used the correct process (proper calculation, consideration of arguments, adequate explanation). Substantive review asks whether the length of the sentence is reasonable. The First Circuit vacated for a procedural flaw and therefore did not reach substantive reasonableness.
• “Heartland” of the Guidelines: The typical set of cases contemplated by a guideline. Courts sometimes justify a variance by explaining why a case falls outside that typical range (e.g., extraordinary ammunition quantity or dangerousness).
• “Principal/dominant argument” requirement: A sentencing court must grapple with a defendant’s key, outcome-relevant point—here, that ammunition without a firearm is allegedly less dangerous.
• Supervised release revocation: Post-imprisonment monitoring with conditions. Violations can lead to revocation and imprisonment; repeated violations can be evidence of heightened recidivism risk even if the violations are not new felonies.
• Guidelines amendment reference (U.S.S.G. app. C, Amend. 821 (Supp. 2023)): The opinion notes the criminal history category changed on remand due to a subsequent Guidelines amendment affecting how points were assessed for committing an offense while on supervised release.

5. Conclusion

United States v. Nieves-Díaz reinforces a core First Circuit sentencing principle: when a district court imposes a significant upward variance, it must provide an explanation robust enough to permit appellate review and must engage with the defendant’s main counterarguments. The opinion’s distinctive contribution is its focus on ammunition-quantity variances in the “novel” posture where no firearm is found—requiring the sentencing court to articulate why the ammunition is aggravating in the specific circumstances, rather than relying on generic statements that the Guidelines do not account for quantity. The decision preserves broad district-court discretion on remand but conditions its exercise on a transparent, individualized record.