Exigent Circumstances Permit Warrantless Real‑Time CSLI During Ongoing Bomb Threats; Overinclusive Rule 404(b) Instruction Not Plain Error — United States v. Mubarak (6th Cir. 2025)

Court: United States Court of Appeals for the Sixth Circuit

Panel: Chief Judge Sutton; Judges Batchelder and Larsen (opinion by Larsen, J.)

Date: October 21, 2025

Publication Status: Not recommended for publication (nonprecedential, but citable for persuasive value)

Introduction

In United States v. Yousif Amin Mubarak, the Sixth Circuit affirmed a jury verdict convicting the defendant of seven counts of transmitting threats in interstate commerce under 18 U.S.C. § 875(c). The case arises from an intense, week-long campaign of threatening and harassing calls to businesses, schools, and officials in and around Canal Winchester, Ohio. On appeal, Mubarak challenged three core rulings:

• Admission of extensive “other acts” evidence—uncharged threatening calls—under Federal Rule of Evidence 404(b) and Rule 403.
• Overinclusive jury instructions describing permissible uses of the Rule 404(b) evidence.
• Admission of real-time cell-site location information (CSLI) obtained without a warrant.

The Sixth Circuit affirmed across the board. Most notably, assuming without deciding that obtaining real-time CSLI is a Fourth Amendment “search,” the court held the warrantless collection was justified by exigent circumstances in the face of ongoing bomb threats—an emergency that did not evaporate simply because the suspect was discovered to be out of state. The court also upheld the admission of uncharged calls under Rule 404(b) and, despite an overinclusive limiting instruction, found no plain error.

Summary of the Opinion

• Rule 404(b) / Rule 403: Evidence of uncharged threatening calls—made with the same phone numbers during the same spree—was admissible to prove identity, intent, and (for certain calls) motive. Any unfair prejudice did not substantially outweigh probative value given the already-grave nature of the charged threats. The court did not reach the “intrinsic evidence” (res gestae) rationale because Rule 404(b)/403 sufficed.
• Jury Instructions (404(b) uses): The trial court’s limiting instructions listed additional purposes (e.g., opportunity, knowledge, preparation, plan, absence of mistake/accident) beyond those in the evidentiary ruling. Reviewing for plain error (no timely objection), the Sixth Circuit found no reversible error because the instructions also identified proper purposes, the defense did not rely on the added purposes, and the evidence of guilt was overwhelming.
• Real-Time CSLI and the Fourth Amendment: The panel declined to decide whether real-time CSLI is a search in light of Carpenter and Skinner. Assuming it was a search, exigent circumstances (active bomb threats) justified the warrantless real-time “pings.” The exigency did not end merely because Mubarak was outside Ohio. Even if continuing pings after the first were improper, any error would be harmless because the initial ping and Mubarak’s statements established the interstate element of § 875(c).
• Disposition: Convictions affirmed; concurrent sentences of 60 months each upheld.

Case Background

Over the course of September 10–16, 2021, Mubarak placed more than a hundred harassing or threatening calls. Targets included:

• County Municipal Judge Andrea Peeples (over multiple days, escalating to a direct death threat).
• Local businesses (e.g., a bar, Home Depot, Best Western) and later two schools (leading to evacuations) with bomb threats.
• The county Sheriff’s Office, including direct threats to a dispatcher, over a sustained period.

The calls often used the same phone numbers and were proximate in time. Mubarak left voicemails identifying himself and stating he was not in Ohio. He was arrested in Oregon. A jury convicted him on seven counts of transmitting threats in interstate commerce—three businesses, two schools, a sheriff, and a judge—and the court imposed concurrent 60‑month terms.

Detailed Analysis

I. Rule 404(b) “Other Acts” Evidence and Rule 403 Balancing

The government introduced evidence of uncharged, contemporaneous threatening calls to several local businesses, as well as to the Sheriff’s Office and Judge Peeples. The district court found the evidence admissible both as intrinsic/res gestae and under Rule 404(b). The Sixth Circuit affirmed on Rule 404(b) and Rule 403 grounds, and therefore did not reach the intrinsic‑evidence rationale.

Governing Standards

• Rule 404(b): Prohibits using other acts to prove propensity but allows admission for non‑character purposes such as motive, intent, identity, knowledge, plan, absence of mistake, etc.
• Huddleston v. United States (1988): When evidence is offered for a proper Rule 404(b) purpose, it is then subject to ordinary relevance and Rule 403 scrutiny.
• Rule 403: Permits exclusion if probative value is substantially outweighed by unfair prejudice. The Sixth Circuit gives trial courts “very broad discretion,” taking “a maximal view” of probative value and “a minimal view” of unfairly prejudicial effect. See United States v. Libbey‑Tipton (2020) and United States v. Sassanelli (1997).
• Standard of Review: The Sixth Circuit acknowledged ongoing intra‑circuit ambiguity as to whether the Rule 404(b) purpose determination is reviewed de novo or for abuse of discretion (contrasting cases include Clay, Mandoka, and Allen). The court found no error under either standard.

Application to Mubarak

• Identity and Intent: Uncharged calls to other local businesses were closely linked to the charged conduct (same numbers, same spree, similar content), supporting the inference that the same person made the charged calls (identity) and did so with the requisite intent.
• Motive: Uncharged calls to the Sheriff’s Office and Judge Peeples reflected animus arising from prior encounters, which was relevant to motive for the charged threats.
• Unfair Prejudice Argument: Mubarak argued risk of prejudice—especially given his Arabic name and accent—by painting him as attempting to “blow up an entire community.” The court held any incremental prejudice was minimal in light of the already‑admitted, unchallenged evidence of multiple bomb threats to local businesses and schools. This was not the “rare case” warranting reversal of the trial court’s Rule 403 judgment call.

Bottom line: The uncharged acts (the spree’s scope and content) were highly probative of identity, intent, and (in part) motive, and their probative value was not substantially outweighed by any unfair prejudice.

II. Overinclusive Limiting Instruction on Rule 404(b) Evidence and Plain-Error Review

The trial court’s cautionary and final instructions listed permissible uses for the Rule 404(b) evidence that exceeded the court’s earlier evidentiary ruling. Specifically, beyond identity, intent, and motive, the instructions referenced opportunity, knowledge, preparation, plan, absence of mistake, and lack of accident—purposes not actually relied on by the court when admitting the evidence. The Sixth Circuit noted this deviates from the Sixth Circuit Pattern Criminal Jury Instruction § 7.13, which directs courts to specify only the purposes for which the evidence was admitted.

Standard of Review and Framework

• Preservation: Although defense counsel objected to admission of the Rule 404(b) evidence, he did not object to the wording of the limiting instructions. Under United States v. Davis (2008) and United States v. Fraser (2006), the lack of an instruction‑specific objection forfeits the issue, triggering plain‑error review.
• Plain Error: The appellant must show a clear error affecting substantial rights, and even then, reversal is discretionary, reserved for errors that seriously affect the fairness, integrity, or public reputation of judicial proceedings. See United States v. Aaron (2009), Greer v. United States (2021), and Puckett v. United States (2009).
• Jury Instruction Plain Error Standard: The court asked whether, taken as a whole, the instructions were so clearly erroneous that they likely produced a “grave miscarriage of justice.” United States v. Robinson (6th Cir. 2025).

Application to Mubarak

• The instructions correctly allowed consideration for identity, intent, and motive—proper purposes here.
• The additional listed purposes (opportunity, knowledge, preparation/plan, absence of mistake/accident) did not match the trial’s live disputes—e.g., the defense did not argue lack of opportunity or mistake.
• Borrowing from United States v. Johnson (1994), where similarly overinclusive and contradictory instructions did not warrant reversal, the court emphasized: proper purposes were identified; there was no timely defense objection after admission; and the evidence of guilt was overwhelming.

Bottom line: While the court cautioned against overbroad limiting instructions, it found no plain error given the circumstances.

III. Real-Time CSLI, Carpenter, Skinner, and the Exigent-Circumstances Exception

The government obtained four hours of real-time CSLI by “pinging” Mubarak’s phone the night of September 12–13, placing him in Washington State. This evidence helped establish the “interstate commerce” element of 18 U.S.C. § 875(c).

The Doctrinal Landscape

• Carpenter v. United States (2018): Government access to historical CSLI is a Fourth Amendment “search.” Carpenter, however, explicitly left open whether access to real-time CSLI is a search.
• United States v. Skinner (6th Cir. 2012): Pre‑Carpenter decision holding access to real-time CSLI is not a search. Carpenter did not expressly overrule Skinner on real‑time data.
• Panel’s Approach: The court declined to decide (1) whether Carpenter’s reasoning extends to real‑time CSLI or (2) whether Carpenter is an intervening decision enabling reconsideration of Skinner. Instead, assuming the real‑time access was a “search,” it held the exigent‑circumstances exception justified the warrantless pinging.

Exigent Circumstances and Ongoing Emergency

• Legal Rule: Warrantless searches are reasonable when exigencies make law enforcement needs compelling—e.g., to protect individuals threatened with imminent harm. Carpenter itself cites bomb threats as classic exigencies. See Carpenter, 585 U.S. at 319–20.
• Standard of Review: Factual findings are reviewed for clear error; legal conclusions de novo. United States v. Pollard (6th Cir. 2000).

Application to Mubarak

• Ongoing Emergency: The court characterized the situation as “an ongoing emergency involving multiple bomb threats.” The threats were active, repeated, and extended to multiple targets (businesses, schools, law enforcement).
• Geographic Distance Does Not Dissipate Exigency: The first ping showing the suspect outside Ohio did not end the emergency. Bombs could have been planted locally; the suspect had claimed to direct others (e.g., “two guys with suicide bombs” at a Best Western) and posed a danger to people wherever he was located.
• Harmless Error Alternative: Even if the exigency did not justify continued pinging after the first location fix, any error would be harmless because:
  • The initial (unchallenged) ping placed Mubarak outside Ohio, satisfying the interstate element of § 875(c); and
  • He repeatedly said he was not in Ohio (e.g., at a girlfriend’s house in Redmond, Washington).

Bottom line: The panel left the doctrinal status of real‑time CSLI unresolved but held exigent circumstances permitted warrantless real‑time tracking during active bomb threats, and in any event, any overcollection beyond the initial ping was harmless.

Precedents and Authorities Cited, and Their Influence

• Huddleston v. United States, 485 U.S. 681 (1988): Clarifies that Rule 404(b) evidence, when offered for a proper purpose, is subject to Rules 402 and 403. Guided the court to conduct a Rule 403 balancing after finding proper non‑propensity purposes.
• United States v. Clay, 667 F.3d 689 (6th Cir. 2012); United States v. Mandoka, 869 F.3d 448 (6th Cir. 2017); United States v. Allen, 619 F.3d 518 (6th Cir. 2010): Reflect the Sixth Circuit’s unsettled standard of review on Rule 404(b) decisions. The panel noted the ambiguity but found no error under either standard.
• United States v. Libbey‑Tipton, 948 F.3d 694 (6th Cir. 2020); United States v. Sassanelli, 118 F.3d 495 (6th Cir. 1997): Emphasize the deferential Rule 403 approach—maximizing probative value and minimizing unfair prejudice—supporting admission of the uncharged calls.
• United States v. Davis, 547 F.3d 520 (6th Cir. 2008); United States v. Fraser, 448 F.3d 833 (6th Cir. 2006): Preservation rules for objections to jury instructions. Because counsel did not object to the wording of the instructions, plain‑error review applied.
• United States v. Aaron, 590 F.3d 405 (6th Cir. 2009); Greer v. United States, 593 U.S. 503 (2021); Puckett v. United States, 556 U.S. 129 (2009): Set out the plain‑error standard and its stringent requirements. The panel used these to reject reversal on the instruction error.
• United States v. Robinson, 133 F.4th 712 (6th Cir. 2025): Articulates the “grave miscarriage of justice” benchmark for plain error in jury instructions. Applied to uphold the verdict.
• United States v. Johnson, 27 F.3d 1186 (6th Cir. 1994): Overinclusive 404(b) instruction did not require reversal where proper purposes were included, there was no objection post‑admission, and the proof of guilt was strong. Directly analogized.
• Carpenter v. United States, 585 U.S. 296 (2018): Historical CSLI is a search; acknowledges exigent‑circumstances exceptions for emergencies like bomb threats. The panel leveraged Carpenter’s exigency discussion to uphold warrantless real‑time CSLI.
• United States v. Skinner, 690 F.3d 772 (6th Cir. 2012): Holds real‑time CSLI is not a search (pre‑Carpenter). The panel did not resolve Skinner’s continued vitality but assumed a search to decide via exigency.
• Ne. Ohio Coalition for the Homeless v. Husted, 831 F.3d 686 (6th Cir. 2016): On when intervening Supreme Court decisions permit revisiting circuit precedent. Cited to note, but not resolve, whether Carpenter allows revisiting Skinner.
• United States v. Pollard, 215 F.3d 643 (6th Cir. 2000): Standard of review for exigent circumstances (clear error for facts; de novo for law). Applied here.
• Sixth Circuit Pattern Criminal Jury Instructions § 7.13: Instructs judges to list only the admissible purposes for Rule 404(b) evidence. The panel flagged the departure from this guidance.

Legal Reasoning: How the Court Reached Its Conclusions

• On 404(b)/403: The spree’s uncharged calls were probative of identity (same phone numbers; similar threats; tight temporal and spatial connection) and intent (demonstrating purposeful communication of threatening content), and certain law‑enforcement/judicial calls showed motive (grievances with specific officials). Under the Sixth Circuit’s Rule 403 approach, the incremental prejudice was minimal relative to the charged bomb threats themselves.
• On the limiting instruction: Although broader than the evidentiary ruling and pattern guidance, the instruction did not push the jury toward propensity reasoning and included proper purposes. Absent a focused objection and given overwhelming evidence, reversal under plain‑error review was unwarranted.
• On real‑time CSLI: The panel avoided weighing in on the unsettled “real‑time CSLI as search” question and instead assumed a search and applied Carpenter’s exigency framework. Active, multi‑target bomb threats constitute a paradigmatic ongoing emergency. Cross‑state location did not negate the threat; nor was any post‑first‑ping collection outcome‑determinative given the interstate element and defendant’s own statements.

Impact and Forward-Looking Implications

1. Fourth Amendment and Digital Location Data

• Practical Green Light in Emergencies: Law enforcement in the Sixth Circuit can take comfort that, at least during bona fide ongoing emergencies such as bomb threats, warrantless real‑time CSLI acquisition will be upheld under the exigent‑circumstances exception.
• Doctrinal Question Remains Open: The panel declined to reconcile Skinner with Carpenter regarding real‑time CSLI. Future, published cases may address whether real‑time CSLI is a search. For now, agencies should continue to evaluate whether exigencies are present and, if time allows, seek warrants to avoid suppression risk.
• Scope and Duration of Exigency: The opinion suggests exigency can persist even when a suspect is located out of state, particularly where threats involve third parties or planted devices. Nonetheless, agencies should document reasons justifying continued pings and reassess necessity as information develops.
• Harmless-Error Backstop: Where the interstate element is satisfied by the first location fix and/or admissions, additional pings may be “harmless” in prosecutions under § 875(c). But harmlessness is case‑specific and not a substitute for careful front‑end justification.

2. Evidence: Rule 404(b) and “Spree” Conduct

• Spree Evidence as Identity/Intent Proof: The decision reinforces that a cluster of closely‑connected, similar acts within a short timeframe—using the same phone numbers and containing similar threats—can be powerful, admissible proof of identity and intent.
• Limiting Instruction Discipline: Trial judges should tailor Rule 404(b) limiting instructions to the precise purposes for which evidence was admitted. Overinclusive lists risk error—even if here the error was not plain.
• Defense Preservation: Defense counsel should specifically object to the language of limiting instructions. A general Rule 404(b) objection may be insufficient to preserve an instructions claim, leaving the defendant to the steep hill of plain‑error review.

3. Practical Takeaways for Stakeholders

• Prosecutors: When confronting spree-like conduct, build the 404(b) record carefully—establish the tight temporal, spatial, and modus links to identity/intent; consider motive when calls target officials with known history.
• Law Enforcement: In emergencies, document exigency contemporaneously and reassess whether the emergency persists as new information (e.g., a first ping) arrives. If feasible, transition to a warrant once the exigency stabilizes.
• Trial Judges: Apply the Sixth Circuit’s “maximal probative/minimal prejudice” lens under Rule 403, but keep limiting instructions aligned with the admission rationale and pattern guidance.
• Defense Counsel: Preserve instruction objections with specificity; if arguing prejudice under Rule 403, identify concrete, case‑specific unfairness beyond the inherent gravity of the charged conduct.

Complex Concepts Simplified

• Rule 404(b) “Other Acts” Evidence: Generally, the jury cannot hear about a defendant’s other bad acts just to infer, “once a bad actor, always a bad actor.” But the same facts can be admitted for non‑character purposes—like proving who did it (identity), why (motive), or with what state of mind (intent).
• Rule 403 Balancing: Even if relevant, evidence can be excluded if its unfair prejudice substantially outweighs its value. “Unfair prejudice” means a tendency to lead the jury to decide on an improper basis (e.g., emotion), not merely that the evidence is damaging.
• Intrinsic (Res Gestae) Evidence: Facts so intertwined with the charged offense that they complete the story of the crime. If evidence is intrinsic, it falls outside Rule 404(b). This panel did not rely on this doctrine.
• Limiting Instruction: A direction telling jurors the specific, lawful reasons they may consider certain evidence, and the reasons they may not.
• CSLI (Cell‑Site Location Information): Data showing which cell towers a phone connects to, enabling inferences about the phone’s location. “Historical” CSLI looks back over time; “real‑time” CSLI pings the phone to learn where it is now.
• Exigent Circumstances: Emergencies allowing warrantless action, such as imminent threats to life or safety (e.g., bomb threats), where waiting for a warrant would risk harm.
• Plain Error: A high bar for unpreserved errors on appeal: the error must be clear, affect substantial rights, and seriously undermine the fairness or integrity of the proceedings.
• Harmless Error: An error that, even if it occurred, did not affect the verdict and thus does not warrant reversal.
• Interstate Commerce Element (§ 875(c)): The statute punishes transmitting threats “in interstate or foreign commerce.” Proof that calls originated outside the state (e.g., via real‑time location or admissions) satisfies this element.

Unresolved Questions and Limits of the Opinion

• Precedential Force: The decision is not recommended for publication; it is persuasive rather than binding within the Sixth Circuit.
• Real‑Time CSLI as “Search”: The court assumed, without deciding, that real‑time CSLI collection is a search. Future published decisions may address whether Carpenter’s reasoning extends beyond historical CSLI.
• Standard of Review for Rule 404(b): The intra‑circuit uncertainty (de novo vs. abuse of discretion for the “proper purpose” determination) remains unresolved.
• Intrinsic Evidence Doctrine: The panel did not reach whether the uncharged calls were admissible as “intrinsic,” leaving doctrinal contours for another day.

Conclusion

United States v. Mubarak offers a measured but meaningful reaffirmation of two principles in federal criminal practice. First, in the face of active, multi‑target bomb threats, warrantless acquisition of real‑time CSLI fits squarely within the exigent‑circumstances exception—even if the suspect is located out of state—particularly where threats involve third parties and potential planted devices. Second, spree‑based other‑acts evidence can be admissible to prove identity, intent, and motive when closely linked to the charged offenses, and overinclusive limiting instructions—while disfavored—will not prompt reversal absent a preserved, prejudicial error.

While nonprecedential, the opinion provides practical guidance to trial courts, law enforcement, and litigants on managing digital‑location evidence during emergencies and on calibrating Rule 404(b) admissions and instructions. It also highlights open doctrinal questions in the wake of Carpenter, particularly the constitutional status of real‑time CSLI outside exigent contexts, setting the stage for future, precedential clarification.