Date: May 5, 2026

Plain-Error Shield for Terry Frisks and Career-Offender Predicates: Aggregated Suspicion and “Realistic Probability” in Louisiana Cocaine Cases

1. Introduction

In United States v. Young (5th Cir. May 1, 2026) (per curiam) (unpublished), Kenric W. Young appealed after a conditional guilty plea to (1) possession with intent to distribute methamphetamine, and (2) possessing a firearm in furtherance of a drug-trafficking crime. Young challenged two rulings: (a) denial of his motion to suppress evidence recovered during a pat-down following a traffic stop, and (b) his designation as a career offender under the Sentencing Guidelines based on two Louisiana cocaine distribution convictions.

The central issues were (i) whether officers had reasonable suspicion that Young was armed and dangerous to justify a Terry frisk during a traffic stop, and (ii) whether a Louisiana cocaine statute is too broad to qualify as a “controlled substance offense” predicate—particularly given arguments that Louisiana’s definition of cocaine encompassed ioflupane.

Critically, Young conceded both objections were not preserved in the district court, forcing the Fifth Circuit to apply plain-error review—a standard that often determines the outcome as much as the underlying merits.

2. Summary of the Opinion

The Fifth Circuit affirmed. On suppression, it held there was no clear or obvious error in concluding officers had reasonable suspicion to frisk Young: the stop occurred at night in a high-crime area; Young did not promptly stop despite lights and sirens; he pulled into an “unknown driveway”; he exited immediately without instruction; there was a passenger; and officers observed a bulge in the front pocket of his sweatshirt.

On sentencing, the court rejected (under plain-error review) Young’s claim that a Louisiana cocaine distribution conviction is not a Guidelines predicate because Louisiana’s cocaine definition allegedly swept more broadly than the federal Controlled Substances Act (CSA) due to ioflupane. Even assuming overbreadth, the court relied on Fifth Circuit precedent requiring a defendant to show a “realistic probability” that the state actually prosecutes the asserted non-generic conduct. Young could not identify such a prosecution, so any error was not “clear or obvious.”

3. Analysis

3.1. Precedents Cited

A. Standards of review and deference

United States v. Keller: Cited for the proposition that an unpreserved suppression claim is reviewed only for plain error. This frames the appeal: Young needed to show an error that was “clear or obvious,” not merely debatable.
United States v. Gibbs: Used to emphasize heightened deference when suppression findings rest on “live oral testimony.” Because the district judge observed witness demeanor, it is harder to show clear error (and even harder to show plain error).

B. Terry frisks during traffic stops

Knowles v. Iowa (citing Terry v. Ohio): Supplies the basic rule that officers may conduct a pat-down during a traffic stop upon reasonable suspicion that an occupant may be armed and dangerous.
United States v. Castillo: Reinforces that “reasonable suspicion is a low threshold,” supporting the court’s acceptance of multiple modest indicators in combination.
District of Columbia v. R.W.: Quoted for the practical, real-world nature of reasonable suspicion— grounded in “everyday life” rather than technical legal parsing.
Michigan v. Long: Cited to highlight the recognized danger of vehicle-related stops and detentions, justifying officer caution.
United States v. Michelletti (en banc): Provides the articulation that officers need not be certain a person is armed; the question is whether a reasonably prudent officer could believe safety is at risk based on “specific and articulable facts.”
United States v. Thomas (citing United States v. Arvizu): Supports the aggregation principle—facts that may be innocent individually can amount to reasonable suspicion in the aggregate.
Illinois v. Wardlow: Supplies two key points the panel uses: high-crime location is a contextual factor in the Terry analysis, and courts permit “commonsense judgments and inferences about human behavior.”
United States v. Rideau: Cited for the practical observation that “weapons and violence abound” in high-crime areas, supporting increased caution.
Maryland v. Wilson: Used for the proposition that a passenger increases potential sources of harm, bolstering the frisk justification.

C. Career offender, categorical approach, CSA benchmark, and overbreadth

Mathis v. United States: Cited for the categorical approach—comparing statutory elements of the prior conviction to the generic Guidelines definition rather than underlying facts.
United States v. Minor: Supplies two crucial points: (1) a statute that covers a “greater swath of conduct” than the generic offense is not a predicate; and (2) because the Guidelines do not define “controlled substance,” the CSA definition “in effect at the time of sentencing for the instant offense” is the reference.
Brown v. United States: Cited for discussion of ioflupane as a “radioactive cocaine derivative” used in medical diagnostics—supporting Young’s theory of potential overbreadth.

D. “Realistic probability” requirement and plain-error posture

United States v. Castillo-Rivera (en banc): The linchpin for rejecting Young’s sentencing claim on plain error. It requires the defendant to show a “realistic probability” that the state applies the statute to non-generic conduct—typically by identifying actual prosecutions or authoritative applications.
United States v. Gladney: Applied directly to ioflupane-style arguments, holding that without examples of state prosecutions, any error is not clear or obvious under plain-error review.
United States v. Taylor: Raised in the opinion’s footnote as a possible tension with United States v. Castillo-Rivera, because some courts have questioned whether Taylor undermines the “realistic probability” requirement in certain contexts.
United States v. Williams: Cited as an example of district-court disagreement about whether United States v. Taylor abrogated United States v. Castillo-Rivera.
United States v. Kerstetter: Cited for limiting Taylor to comparisons between two federal statutes and rejecting its use where one statute is state law.
United States v. Augillard: Cited for the Fifth Circuit’s conclusion that neither United States v. Taylor nor Brown v. United States abrogated United States v. Castillo-Rivera.

3.2. Legal Reasoning

A. Suppression: why the frisk was upheld

The panel’s suppression analysis is best understood as a two-step filter:

Substantive Fourth Amendment rule: Under Terry v. Ohio as carried through Knowles v. Iowa, officers may frisk during a traffic stop if they have reasonable suspicion that the person is armed and dangerous. The court stresses that this is a “low threshold” (United States v. Castillo) and turns on practical inference rather than technicalities (District of Columbia v. R.W.).
Procedural overlay: plain error + deference: Because Young did not preserve the objection, he had to show a clear or obvious mistake, and the court also invoked strong deference where the district court relied on live testimony (United States v. Gibbs). This combination makes reversal unlikely unless the frisk was plainly unjustified.

On the facts, the court did not treat the sweatshirt “bulge” as sufficient by itself; it treated the bulge as one factor in an aggregate inference. The court relied on the high-crime context (Illinois v. Wardlow; United States v. Rideau), the inherent danger of vehicle stops (Michigan v. Long), Young’s delayed yielding to emergency lights, his choice to pull into a driveway rather than promptly stop, his immediate exit without instruction, and the presence of a passenger (Maryland v. Wilson). Under United States v. Thomas and United States v. Arvizu, these arguably innocent facts can accumulate into reasonable suspicion.

Young’s key counterargument—that pockets commonly contain innocuous items and thus a pocket bulge should not trigger a frisk—was rejected as too abstract. The court responded with Wardlow’s “commonsense judgments” framing: pockets can also conceal weapons, and the broader context made officer concern reasonable.

B. Sentencing: why the career-offender challenge failed

The panel accepted the structure of Young’s theory: under the categorical approach (Mathis v. United States), if Louisiana’s definition of cocaine covered ioflupane (and the CSA definition used for Guidelines purposes did not), then Louisiana’s statute might be overbroad relative to the generic “controlled substance offense” definition as operationalized by the CSA at the time of sentencing (United States v. Minor).

But the court did not decide the overbreadth question on the merits. Instead, it resolved the case on plain-error principles using Fifth Circuit doctrine: even with a plausible textual overbreadth argument, a defendant must show a “realistic probability” the state would actually prosecute the non-generic conduct (United States v. Castillo-Rivera). Young offered no Louisiana cases prosecuting distribution of ioflupane (or otherwise applying the statute outside the CSA-aligned definition). Therefore, any misclassification was not “clear or obvious,” especially in light of the Fifth Circuit’s own ioflupane-related decision in United States v. Gladney.

The footnote underscores an additional procedural point: even if one believes United States v. Taylor undermines United States v. Castillo-Rivera, the panel stressed Young did not make that argument, and in any event the existence of judicial disagreement (citing United States v. Williams) cuts against “clear or obvious” error. The panel also pointed to Fifth Circuit authority narrowing Taylor’s reach (United States v. Kerstetter) and reaffirming that Taylor and Brown do not abrogate Castillo-Rivera (United States v. Augillard).

3.3. Impact

Fourth Amendment (frisks in traffic stops): The opinion reinforces that, in the Fifth Circuit, courts may uphold frisks based on the totality of contextual factors—high-crime area, delayed compliance, atypical behavior (exiting without instruction), passengers, and observable bulges—even when any single factor could be innocently explained. The decision is especially significant in practice because it signals how hard it is to overturn suppression rulings on appeal under plain error, particularly when the district court credited live testimony.
Sentencing (career offender predicates and ioflupane arguments): The opinion continues the Fifth Circuit’s trajectory of requiring a realistic probability showing for state-statute overbreadth arguments—even when defendants point to ioflupane-related mismatches discussed in Brown v. United States. On appeal, absent preserved error and absent state cases demonstrating broader enforcement, defendants will struggle to establish “clear or obvious” error.
Doctrinal stability amid Taylor debate: By citing United States v. Kerstetter and United States v. Augillard, the panel signals that (at least in this circuit) United States v. Taylor is not a general-purpose tool to displace United States v. Castillo-Rivera in state-statute categorical cases. That reduces the likelihood of successful Taylor-based challenges in Fifth Circuit sentencing appeals unless and until the Supreme Court speaks more directly to the “realistic probability” requirement for state statutes.

4. Complex Concepts Simplified

Plain error: A demanding appellate standard applied when a party failed to object in the trial court. The appellant must show an error that is not just wrong, but “clear or obvious,” and that it affected substantial rights (and typically that it seriously affects the fairness or integrity of proceedings). In Young, this standard did much of the work.
Reasonable suspicion: A lower threshold than probable cause. Officers need specific, articulable facts that, taken together, reasonably suggest danger or criminal activity. The court emphasized it is grounded in practical judgment (District of Columbia v. R.W.) and may arise from aggregated innocuous facts (United States v. Thomas; United States v. Arvizu).
Terry frisk / pat-down: A limited search of outer clothing for weapons, permitted during a stop when officers reasonably suspect the person is armed and dangerous (Terry v. Ohio; Knowles v. Iowa).
Categorical approach: A method for deciding whether a prior conviction qualifies as a sentencing predicate by comparing the statute’s elements to the “generic” definition used in federal law, ignoring the particular facts of what the defendant did (Mathis v. United States).
Overbreadth (in the categorical sense): A state statute is “overbroad” if it criminalizes more conduct than the generic federal definition—meaning someone could be convicted under state law for conduct that would not qualify under the federal predicate definition (United States v. Minor).
Realistic probability test: A Fifth Circuit requirement that, even if statutory text seems broader, a defendant must show the state actually applies the statute to the broader conduct—often by identifying cases or authoritative examples (United States v. Castillo-Rivera). Young failed here because he provided no Louisiana prosecution involving ioflupane distribution.

5. Conclusion

United States v. Young illustrates how appellate outcomes can turn on posture. On suppression, the Fifth Circuit reaffirmed that a Terry frisk during a traffic stop may be justified by a constellation of contextual risk factors—particularly in high-crime settings and where driver behavior heightens uncertainty—and that such determinations are hard to upset on plain-error review. On sentencing, the court reinforced that ioflupane-based overbreadth arguments against Louisiana cocaine predicates will not succeed on plain error without a United States v. Castillo-Rivera-style “realistic probability” showing, especially given the Fifth Circuit’s continued view (via United States v. Augillard) that United States v. Taylor and Brown v. United States do not abrogate Castillo-Rivera in state-statute categorical cases.