United States v. Harris: Probable Cause from Lane-Change Violations and Marijuana Odor in the Post-Hemp Era

I. Introduction

In United States v. Michael Harris, No. 24-5944 (6th Cir. Dec. 19, 2025) (unpublished), the United States Court of Appeals for the Sixth Circuit addressed two recurring Fourth Amendment questions:

When does a traffic maneuver involving a dedicated left-turn lane give officers probable cause to make a traffic stop?
Does the odor of burnt marijuana alone still provide probable cause to search a vehicle, notwithstanding the legalization of hemp?

The case arose from a joint federal–local firearms operation at a gun show in Knoxville, Tennessee. Officers suspected that Michael Harris was involved in unlawful firearms activity (possibly a straw purchase) and followed him from the gun show, looking for a traffic violation that would justify a pretextual stop. They asserted that Harris made an improper left turn from a straight-only lane instead of using a marked left-turn lane. During the ensuing stop, an officer smelled burnt marijuana, searched the vehicle, and ultimately uncovered firearms, ammunition, and nearly a kilogram of methamphetamine.

Harris moved to suppress the evidence, arguing that:

there was no lawful basis for the traffic stop; and
even if the stop was lawful, the odor of burnt marijuana did not create probable cause to search the vehicle in light of legal hemp.

The district court denied the motion to suppress, and Harris entered a conditional guilty plea, preserving his right to appeal that ruling. The Sixth Circuit affirmed, offering a pointed application of Tennessee traffic law, the collective-knowledge doctrine, and a recent published decision (United States v. Santiago) regarding marijuana odor in the hemp era.

II. Summary of the Opinion

Judge Boggs, writing for a unanimous panel (Judges Boggs, Bush, and Readler), affirmed the denial of the motion to suppress and Harris’s convictions. The court held:

Traffic stop: The officers had probable cause to stop Harris’s vehicle because Detective Marcus Parton personally observed Harris making an “immediate and abrupt” left turn from a straight-only lane, cutting across a marked left-turn lane, in violation of Tenn. Code Ann. § 55‑8‑140(5)(a). The district court’s decision to credit Parton’s testimony was not clearly erroneous.
Collective knowledge: Even though Parton did not personally conduct the stop, his knowledge of the traffic violation was properly imputed to the officers who executed the stop under the “collective knowledge” doctrine.
Vehicle search: The odor of burnt marijuana detected by an officer as he approached the vehicle provided probable cause to search it. The panel considered itself bound by United States v. Santiago, 139 F.4th 570 (6th Cir. 2025), which held that a marijuana-like odor, even after hemp legalization, establishes probable cause that marijuana is present.
Result: Because both the stop and search were lawful, the evidence was admissible. The court therefore affirmed Harris’s convictions for possession with intent to distribute methamphetamine and being a felon in possession of firearms and ammunition.

III. Factual and Procedural Background

A. Gun Show Surveillance and Initial Suspicion

On April 24, 2022, officers from the Knox County Sheriff’s Office (KCSO), Knoxville Police Department (KPD), and the Bureau of Alcohol, Tobacco, and Firearms (ATF) conducted a joint undercover operation at a gun show in the Knoxville Expo Center. Their mission was to detect illegal gun activity, particularly straw purchases—transactions in which a person legally eligible to buy a firearm acquires it on behalf of someone who is prohibited from possessing guns.

Undercover officers observed a man walking from booth to booth, showing and describing firearms via FaceTime to someone not physically present. Officers considered this behavior indicative of a possible straw purchasing scheme: the unseen person could be directing the purchases while avoiding the background check and paperwork.

After the man purchased multiple firearms and left the gun show, officers followed him. They ran his out-of-state plates and discovered the vehicle was a rental, further heightening suspicion. At some point, the vehicle pulled into a Popeyes restaurant. Some radio transmissions indicated that the van went through the drive-through and left with food. Detective Parton, however, testified that he only saw the vehicle enter and exit the parking lot, leading him to believe this was a “heat check”—a counter-surveillance maneuver to see whether law enforcement was tailing him.

B. The Alleged Traffic Violation

Parton followed the vehicle to an intersection that had:

a designated straight-only lane (a through-lane), and
a separate designated left-turn lane.

Parton, in the through-lane behind the van, testified that when the light turned green, the van “immediately and abruptly” turned left from that lane, cutting across the marked left-turn lane. Under Tennessee law, when a special lane for left turns has been established, drivers must use that lane to turn left unless they “cannot safely enter” it. Tenn. Code Ann. § 55‑8‑140(5)(a).

Parton radioed that the driver had just made an illegal left turn. KPD officers, relying on that radioed information, followed the van to a gas station and conducted a traffic stop.

C. The Stop, Odor, and Search

At the gas station, officers approached the vehicle and found Harris in the driver’s seat, with a passenger. One officer detected a strong odor of burnt marijuana coming from the open window. On that basis, the officer told Harris he intended to search the van. When questioned, Harris admitted that he and his passenger had likely smoked marijuana the day before.

The officer then instructed Harris to step out of the vehicle for a frisk. Officers searched the van and discovered:

three wads of cash,
two cell phones,
a marijuana grinder,
ammunition, firearms, and firearm accessories, and
a pink suitcase.

When an officer began to search the suitcase, Harris re-entered the van and fled the scene, quickly crashing into two other vehicles. At the crash site, the officer finished searching the suitcase and found nearly one kilogram of methamphetamine.

D. District Court Proceedings

Harris was federally indicted for:

possession with intent to distribute 50 grams or more of methamphetamine,
possession of firearms in furtherance of a drug-trafficking offense, and
being a felon in possession of firearms and ammunition.

He moved to suppress all evidence resulting from the stop and search, contending:

Officers lacked reasonable suspicion or probable cause to justify the traffic stop—he disputed that he had committed a traffic violation;
Even if the stop were valid, the odor of burnt marijuana, indistinguishable from legal hemp, did not provide probable cause to search the car.

After an evidentiary hearing, the district court credited Detective Parton’s description of the turn, found that Harris had violated § 55‑8‑140(5)(a), and concluded that the officers had probable cause to stop the vehicle. The court also held that the odor of burnt marijuana established probable cause to search the vehicle. It therefore denied the motion to suppress.

Harris then pleaded guilty to possession with intent to distribute methamphetamine and being a felon in possession of firearms and ammunition, preserving his right to appeal the suppression ruling. He apparently did not pursue the firearms-in-furtherance charge in light of the plea structure. On appeal, Harris challenged only the denial of his suppression motion.

IV. Standards of Review and Framework

The Sixth Circuit began by reiterating the basic structure of appellate review for suppression rulings:

Findings of fact: Reviewed for clear error. Under United States v. Navarro-Camacho, 186 F.3d 701, 705 (6th Cir. 1999), a factual finding is clearly erroneous only when the appellate court, after reviewing the record, has a “definite and firm conviction that a mistake has been committed.”
Conclusions of law: Reviewed de novo, per United States v. Ickes, 922 F.3d 708, 710 (6th Cir. 2019). That means the appellate court gives no deference to the district court’s legal interpretations.
View of the evidence: When the district court denies a motion to suppress, the appellate court must review the evidence “in the light most favorable to the government.” United States v. Gunter, 551 F.3d 472, 479 (6th Cir. 2009).

This framework is crucial: Harris’s appeal was largely a frontal attack on the district court’s view of the facts—especially Detective Parton’s credibility and the characterization of the traffic maneuver. Under clear-error review and the government-favorable lens, such factual challenges are difficult to win.

V. Analysis of the Court’s Holdings

A. Legality of the Traffic Stop

1. Fourth Amendment and Pretextual Stops

The court grounded its analysis in the Fourth Amendment’s protection against “unreasonable searches and seizures” and the longstanding rule, from Katz v. United States, 389 U.S. 347, 357 (1967), that warrantless searches and seizures are per se unreasonable unless they fit within a recognized exception.

One such exception is the authority to conduct a warrantless traffic stop if officers have probable cause to believe a traffic violation has occurred. As the Supreme Court held in Whren v. United States, 517 U.S. 806, 810 (1996), the subjective motivation of the officers—here, their interest in potential firearm offenses—is irrelevant so long as there is objective probable cause for the traffic stop.

Thus, even assuming the officers were intentionally “looking for” a pretextual traffic violation to investigate Harris’s suspected gun activity, that tactic is constitutionally permissible if a real traffic infraction occurred.

2. Tennessee Left-Turn Lane Law

The key state-law provision is Tenn. Code Ann. § 55‑8‑140(5)(a), which provides in relevant part:

“Where a special lane for making left turns ... has been established[,] a left turn shall not be made from any other lane unless a vehicle cannot safely enter the turn lane[.]”

The statute does two things:

It imposes a general rule: If a left-turn lane exists, you must use it when turning left.
It creates a narrow exception: A driver may turn left from a different lane only if it is not safe to enter the designated turn lane.

Detective Parton testified that:

Harris was in the straight-only lane when he stopped at the red light,
There was a left-turn lane available,
When the light turned green, Harris “immediately and abruptly” turned left, cutting across the left-turn lane instead of using it, and
To the best of Parton’s knowledge, there were no other vehicles in the left-turn lane, so it was available and safe to use.

Based on that testimony, the panel held that Harris’s conduct “falls squarely within the plain text of the statute.” He turned left from the straight-only lane despite the presence of an available, safe left-turn lane—precisely what § 55‑8‑140(5)(a) forbids.

3. The “Unsafe Entry” Exception and Credibility

Harris argued that the lane configuration and his positioning might have allowed an interpretation whereby he entered the left-turn lane before turning, or that the lane might not have been safe to enter. The Sixth Circuit rejected this, emphasizing:

The district court credited Parton’s testimony that there were no other cars in the left-turn lane, and that the turn was made directly from the straight-only lane across the turn lane.
Under Gunter, any ambiguity in the testimony must be resolved in favor of the government when the suppression motion has been denied.
Harris offered no evidence contradicting Parton’s account beyond his own appellate argument.

In a footnote, the court addressed Harris’s argument that Parton’s testimony could be “interpreted differently.” Harris focused on Parton’s statement that the vehicles were “within the area to be in the turn lane” and “weren’t so far back from the light that you couldn’t make your way to the turn lane.” Harris tried to spin that into suggesting he was or could lawfully be in the left-turn lane when he turned.

The panel rejected this reading, explaining that Parton was merely clarifying that, before stopping, the vehicles were at a point on the road where entering the turn lane would have been possible and lawful—not that Harris actually did so. Parton further testified that Harris’s vehicle stopped “pretty close up to the white line at the red light,” supporting the view that he was in the straight-only lane at the stop and then cut across the turn lane when the light changed.

Because there was no clear error in the district court’s credibility determinations or factfinding, the appellate court was bound to accept the factual premise that a violation of § 55‑8‑140(5)(a) occurred.

4. Probable Cause and Collective Knowledge

Having concluded that a traffic violation occurred, the court held that there was probable cause to stop the vehicle. Importantly, Detective Parton did not personally execute the stop; instead, two KPD officers acted on his radioed report of an “illegal turn.”

The panel invoked United States v. Lyons, 687 F.3d 754, 765–66 (6th Cir. 2012), to rely on the collective-knowledge doctrine. Under that doctrine:

The knowledge and observations of one officer can be imputed to other officers who act in reliance on that information, especially in coordinated investigations.
The officer who actually performs the stop need not personally witness the traffic violation, so long as another officer involved in the investigation did and communicated that information.

Thus, Parton’s probable cause to believe a traffic violation occurred was properly imputed to the KPD officers who made the stop. This allowed the stop to pass Fourth Amendment scrutiny even if the stopping officers did not independently observe the traffic infraction.

B. Probable Cause to Search: Odor of Burnt Marijuana in the Hemp Era

1. Harris’s Argument: Marijuana vs. Hemp Odor

Harris’s second principal argument was that in a legal landscape where hemp is lawful and smells like marijuana, the odor of burnt marijuana alone no longer provides probable cause to search a vehicle. In other words, if the smell could equally indicate legal conduct (hemp) or illegal conduct (marijuana), it should not, by itself, justify an intrusive search.

2. The Court’s Reliance on United States v. Santiago

The panel rejected Harris’s position by relying on a recent published decision: United States v. Santiago, 139 F.4th 570 (6th Cir. 2025). While Santiago involved probable cause for an arrest rather than a vehicle search, the panel emphasized two core points from that case:

The officers in Santiago testified they had never encountered anyone smoking hemp in the field. Based on that experience, the court concluded that to a reasonable officer, a marijuana-like odor overwhelmingly indicates marijuana, not hemp.
The Santiago court further stated that, in both search and arrest contexts, officers have probable cause to believe “that marijuana is present where they smell it.”

By quoting and embracing this language, the panel in Harris treated Santiago as controlling on the broader question of whether marijuana odor alone can establish probable cause. It held that the odor of burnt marijuana emanating from Harris’s vehicle gave officers probable cause to believe that marijuana was present, which in turn justified a search of the vehicle.

The panel expressly invoked the Sixth Circuit’s “prior panel” rule, referencing Moltan Co. v. Eagle-Picher Indus., Inc., 55 F.3d 1171, 1176 (6th Cir. 1995): a later panel is bound by a published decision of an earlier panel unless overruled by the court en banc or by the Supreme Court. Thus, any theoretical argument that hemp legalization should change the probable-cause analysis was foreclosed by Santiago.

3. Fourth Amendment Vehicle Search Doctrine (Implied but Not Elaborated)

Although the opinion does not spell out the specific doctrinal label, the search of Harris’s vehicle fits cleanly within the well-known automobile exception to the warrant requirement:

If officers have probable cause to believe a vehicle contains evidence of a crime, they may search it without a warrant.
The odor of marijuana (or marijuana-like odor treated as marijuana under Santiago) supplies that probable cause.

Thus, once the officer smelled burnt marijuana and Harris essentially confirmed recent marijuana use, the automobile exception authorized a warrantless search of the vehicle, including containers (such as the pink suitcase) where drugs might reasonably be found.

C. The Court’s Treatment of Harris’s Counterarguments

Harris’s counterarguments were largely factual or policy-oriented:

He disputed the officer’s description of the traffic maneuver, suggesting alternative interpretations.
He argued that hemp legalization restricts the logical power of marijuana-like odor to establish probable cause.

The panel dismissed these arguments mostly on doctrinal grounds:

On the facts of the traffic stop, the court deferred to the district court’s credibility resolution and factfinding. Under clear-error review, reweighing witness credibility is exceedingly difficult.
On the hemp-odor issue, the panel declared itself “bound” by Santiago, foreclosing substantial re-argument in a three-judge panel setting.

The resulting opinion is thus more an application and consolidation of existing doctrine than a rethinking of Fourth Amendment principles.

VI. Precedents Cited and Their Role

1. Katz v. United States, 389 U.S. 347 (1967)

Katz stands for the principle that warrantless searches and seizures are presumptively unreasonable, subject to “a few specifically established and well-delineated exceptions.” The Harris panel cites Katz to frame the analysis: both the traffic stop and the vehicle search had to fit within established exceptions (traffic-stop authority, automobile exception) or they would violate the Fourth Amendment.

2. Whren v. United States, 517 U.S. 806 (1996)

Whren held that as long as police have probable cause to believe a traffic violation has occurred, the stop is valid regardless of the officer’s subjective motives (such as a desire to investigate other crimes).

This is critical for operations like the gun show surveillance here. Officers openly sought a traffic violation as a pretext for further investigation. Under Whren, that is constitutionally permissible so long as a real violation—here, the lane-change violation under Tennessee law—did occur.

3. United States v. Ickes, 922 F.3d 708 (6th Cir. 2019)

The panel cites Ickes for the basic standard of review: mixed standard—clear error for facts, de novo for legal conclusions—in appeals of suppression decisions. The citation underscores the deference afforded to trial courts on factual matters.

4. United States v. Navarro-Camacho, 186 F.3d 701 (6th Cir. 1999)

Navarro-Camacho provides the classic articulation of clear-error review: a factual finding is clearly erroneous only if the reviewing court has a firm conviction that an error occurred, even if there is evidence supporting the finding. This high bar anchors the court’s refusal to disturb the district court’s acceptance of Parton’s testimony.

5. United States v. Gunter, 551 F.3d 472 (6th Cir. 2009)

Gunter instructs that when a suppression motion is denied, the appellate court must view the evidence “in the light most favorable to the government.” This rule, combined with clear-error review, significantly limited Harris’s ability to recharacterize the intersection scene and Parton’s observations.

6. United States v. Lyons, 687 F.3d 754 (6th Cir. 2012)

Lyons is the key Sixth Circuit authority on the collective-knowledge doctrine, confirming that information possessed by one officer may be imputed to others for purposes of reasonable suspicion or probable cause, especially in coordinated law-enforcement operations. In Harris, this meant the stopping officers did not need to have personally seen the traffic violation; Parton’s knowledge sufficed.

7. United States v. Santiago, 139 F.4th 570 (6th Cir. 2025)

Santiago is the central precedential pillar for the marijuana-odor issue. As described in the opinion:

It rejected an argument materially identical to Harris’s—namely, that hemp legalization undermines the evidentiary force of a marijuana-like odor.
It credited officer testimony that they had never encountered anyone smoking hemp, making it reasonable to infer marijuana use from such an odor.
It concluded that, for a reasonable officer, a marijuana-like odor is sufficiently indicative of marijuana to create probable cause.
It broadly stated that officers have probable cause to believe “that marijuana is present where they smell it,” in both arrest and search contexts.

In Harris, the panel treated this language as binding on the question of probable cause to search a vehicle based on odor alone.

8. Moltan Co. v. Eagle-Picher Indus., Inc., 55 F.3d 1171 (6th Cir. 1995)

Moltan is cited for the Sixth Circuit’s prior-panel rule: a published panel decision binds subsequent panels unless overturned en banc or by the Supreme Court. This doctrinal rule prevented the Harris panel from crediting Harris’s hemp-based argument; any reevaluation of Santiago would require en banc review or intervention from the Supreme Court.

VII. Complex Concepts Simplified

1. Probable Cause vs. Reasonable Suspicion

Reasonable suspicion is a lower standard—specific and articulable facts suggesting criminal activity, sufficient to justify a brief stop (e.g., a Terry stop).
Probable cause is a higher standard—facts and circumstances that would lead a reasonable person to believe that a crime has been, is being, or will be committed, or that evidence of a crime will be found in a particular place.

In Harris:

Probable cause to believe a traffic violation occurred justified the stop.
Probable cause to believe marijuana was present (based on odor) justified the vehicle search.

2. Pretextual Stops

A “pretextual stop” occurs when officers use a minor legal violation (like a traffic infraction) as a legal entry point to investigate more serious suspected crimes. Under Whren, this is constitutional so long as the traffic infraction is real and provides objective probable cause to stop the vehicle.

3. Collective Knowledge Doctrine

Under this doctrine, officers in a joint operation can pool their knowledge. If one officer has probable cause or reasonable suspicion and communicates that to others, the others may lawfully act on it even if they lack personal knowledge of the underlying facts. This doctrine reflects the reality of modern, coordinated policing.

4. Clear-Error Review

An appellate court does not retry factual disputes. Under clear-error review:

The trial judge, who heard live testimony and could assess demeanor, is given substantial deference.
The appeals court will overturn factual findings only when it is strongly convinced that the trial court made a mistake.

In practical terms, this means that once the district court believed Detective Parton’s description of the left turn, Harris’s ability to argue otherwise on appeal was very limited.

5. Automobile Exception

The automobile exception allows officers to search a vehicle without a warrant if they have probable cause to believe it contains evidence of a crime. This flows from the vehicle’s inherent mobility and the reduced expectation of privacy in automobiles. In Harris, the odor of burnt marijuana provided that probable cause.

6. Nonprecedential (Unpublished) Decisions

The opinion is marked “NOT RECOMMENDED FOR PUBLICATION.” In the Sixth Circuit, such decisions are generally nonprecedential: they do not bind future panels the way published opinions like Santiago do. They may still be cited and can have persuasive value, especially on fact-specific applications of settled law.

VIII. Impact and Future Implications

A. Reinforcing the Role of Traffic Violations in Criminal Investigations

Harris reaffirms that relatively minor traffic infractions—such as improper use of a turn lane—can provide a constitutional gateway to major criminal prosecutions (drugs, guns, etc.). This follows the logic of Whren and underscores:

The importance of detailed officer testimony about traffic configuration and driver behavior;
The deference appellate courts will give to district courts in resolving factual disputes about such maneuvers.

Going forward, defendants challenging traffic stops in the Sixth Circuit will continue to confront the dual obstacles of:

fact deference (clear-error review), and
the requirement that the evidence be viewed in the light most favorable to the government after a suppression denial.

B. Odor of Marijuana After Hemp Legalization

Perhaps the most significant doctrinal reinforcement is the panel’s unambiguous alignment with Santiago:

The odor of burnt (or marijuana-like) plant material emanating from a vehicle, by itself, constitutes probable cause to believe that marijuana is present, notwithstanding the theoretical possibility of hemp.
That probable cause is sufficient for both arrests and vehicle searches in the Sixth Circuit.

Unless and until Santiago is revisited en banc or overruled by the Supreme Court, defense arguments that hemp legalization has eroded the probable-cause value of marijuana odor are effectively foreclosed within this circuit. This has practical consequences:

Officers can continue to rely on odor-based probable cause for stops, searches, and arrests involving suspected marijuana.
Defendants will need to focus on undermining the factual premise (e.g., denying that any odor was present, or challenging officer credibility), rather than arguing that odor cannot legally support probable cause.

C. Application of the Collective-Knowledge Doctrine

The opinion’s use of the collective-knowledge doctrine signals continued judicial support for team-based enforcement practices. In coordinated operations—whether involving guns, drugs, or other offenses—agencies can divide roles (surveillance, traffic stop, arrest, etc.) without jeopardizing the legality of the stop, so long as at least one officer has the requisite probable cause or reasonable suspicion and that information is shared.

D. Limited Precedential Force but Practical Significance

Though Harris is unpublished and nonprecedential, it:

illustrates how trial courts in the circuit are expected to apply Santiago and Whren, and
clarifies the application of Tenn. Code Ann. § 55‑8‑140(5)(a) in the federal context.

Practitioners in Tennessee and the broader Sixth Circuit can treat the case as a practical guide to:

how lane-use violations will be evaluated in suppression hearings; and
how resistant the court is likely to be to hemp-based attacks on odor-derived probable cause.

IX. Conclusion

United States v. Harris does not dramatically reshape Fourth Amendment doctrine. Instead, it consolidates and applies existing law, particularly:

Whren’s approval of pretextual traffic stops based on objective traffic violations;
Santiago’s holding that a marijuana-like odor continues to create probable cause even after hemp legalization;
the collective-knowledge doctrine’s imputation of one officer’s observations to others; and
the stringent standards of appellate review for suppression decisions.

The case underscores several practical lessons:

Traffic infractions remain powerful investigative tools. A seemingly minor lane-use violation can open the door to discovering serious gun and drug offenses.
Officer credibility at suppression hearings is critical. Once the district court credits an officer’s account of a traffic maneuver or perceived odor, appellate reversal is unlikely.
Odor of marijuana retains strong evidentiary force in the Sixth Circuit. Despite the legalization of hemp, the circuit’s current law treats marijuana-like odor as sufficient probable cause for both arrests and vehicle searches.
Coordinated enforcement remains doctrinally supported. The collective-knowledge doctrine ensures that multi-officer operations are not hamstrung by who personally sees or smells what, so long as information is communicated within the team.

Taken together, these principles reinforce a robust law-enforcement toolkit in the Sixth Circuit, while illustrating that challenges to traffic-stop and odor-based probable cause will face substantial doctrinal headwinds absent new en banc or Supreme Court guidance.