Odor of Marijuana Is a Factor—but Not Probable Cause—for Vehicle Searches in Michigan: People v. Armstrong

Introduction

In People of Michigan v. Jeffery Scott Armstrong, the Michigan Supreme Court decisively recalibrated the Fourth Amendment analysis applicable to marijuana odor during vehicle encounters. The Court held that, after the Michigan Regulation and Taxation of Marihuana Act (MRTMA), the smell of marijuana—standing alone—no longer supplies probable cause to search a motor vehicle under the automobile exception. Instead, odor is one circumstance within the totality that may contribute to probable cause.

The case arose from a Detroit encounter in which officers approached a parked Jeep after an officer reported smelling burnt marijuana. After surrounding the vehicle, officers removed passenger Jeffery Armstrong, and a handgun was later recovered from beneath the front passenger seat. The trial court suppressed the firearm and dismissed the case; the Court of Appeals affirmed; and the Michigan Supreme Court—over a dissent—affirmed as well, announcing an important modification to state search-and-seizure doctrine in light of Michigan’s legalization regime.

Key issues included: (1) whether People v. Kazmierczak’s rule—that marijuana odor alone establishes probable cause to search a vehicle—survives the MRTMA; (2) whether the officers’ actions were justified under Terry v. Ohio as an investigatory stop supported by reasonable suspicion; and (3) whether the firearm was lawfully seized under the plain-view doctrine. The Court’s answers will now steer day-to-day policing and litigation in Michigan’s post-legalization landscape.

Summary of the Opinion

In a majority opinion by Justice Cavanagh, joined by Chief Justice Clement and Justices Bernstein, Welch, and Bolden, the Court held:

Kazmierczak’s categorical rule that the smell of marijuana alone supplies probable cause to search a vehicle is “no longer good law” after the MRTMA. Odor is a factor that may contribute to probable cause, but cannot, without more, establish it.
Because the officers relied solely on odor to search, the automobile exception did not apply; the search was unconstitutional and the firearm had to be suppressed.
Although the lower courts erred by demanding probable cause (rather than reasonable suspicion) to justify the initial seizure, it was unnecessary to decide whether odor alone provides reasonable suspicion under Terry in this case.
Assuming arguendo a lawful Terry stop, the trial court did not clearly err in finding the gun was discovered during a search rather than in plain view. The plain-view doctrine is a seizure doctrine; it cannot justify a search. A search requires probable cause, which was lacking here.
The suppression order and dismissal were properly affirmed.

Justice Zahra dissented. He would have avoided revisiting Kazmierczak, remanded for proper consideration of a Terry stop and potential plain-view discovery, and maintained that odor can still supply probable cause in at least some post-MRTMA scenarios. Justice Thomas did not participate.

Analysis

Precedents and Authorities Cited

People v. Kazmierczak, 461 Mich 411 (2000): Previously held that marijuana odor alone may establish probable cause to search a vehicle under the automobile exception. Armstrong declares that rule “no longer viable” post-MRTMA.
MRTMA, MCL 333.27951 et seq.: Legalizes possession and use by adults 21+ within defined limits. Critically, MCL 333.27955(1) states that permitted acts “are not grounds for search or inspection” and “are not grounds for arrest, prosecution, or penalty.” Prohibited conduct persists, including consuming in public or in a vehicle’s passenger area (MCL 333.27954(1)(e) & (g)), and operating under the influence (MCL 333.27954(1)(a); see also MCL 257.625(1)).
MMMA, MCL 333.26421 et seq.: Earlier medical framework that led the Court of Appeals to temper but not discard Kazmierczak. See People v. Anthony, 327 Mich App 24 (2019) (odor plus facts pointing to illegal use in public supported probable cause), and People v. Moorman, 331 Mich App 481 (2020) (odor plus deception supported probable cause that possession fell outside MMMA).
Automobile exception: Pennsylvania v. Labron, 518 US 938 (1996) (warrantless vehicle search permitted when vehicle is readily mobile and probable cause exists).
Probable cause doctrine: Illinois v. Gates, 462 US 213 (1983) (totality-of-circumstances; fair probability); Dist. of Columbia v. Wesby, 583 US 48 (2018) (assess all circumstances, not whether conduct is “innocent”), and Ybarra v. Illinois, 444 US 85 (1979) (probable cause must be particularized to the place/person).
Terry stop and reasonable suspicion: Terry v. Ohio, 392 US 1 (1968); People v. Prude, 513 Mich 377 (2024); People v. Pagano, 507 Mich 26 (2021); People v. Jenkins, 472 Mich 26 (2005); People v. Oliver, 464 Mich 184 (2001).
Plain view: People v. Champion, 452 Mich 92 (1996) (lawful vantage point and immediately apparent incriminating character; plain view authorizes seizure, not search).
Ordering occupants out: Pennsylvania v. Mimms, 434 US 106 (1977) (driver); Maryland v. Wilson, 519 US 408 (1997) (passengers); People v. Armendarez, 188 Mich App 61 (1991).
Burden and standards: People v. Reed, 393 Mich 342 (1975) (prosecution bears burden to justify warrantless conduct); People v. Hammerlund, 504 Mich 442 (2019) (appellate standards); People v. Lucynski, 509 Mich 618 (2022) (warrantless searched/seizures presumed unreasonable); People v. Slaughter, 489 Mich 302 (2011).
Converging state authority post-legalization: Commonwealth v. Barr, 266 A.3d 25 (Pa. 2021); People v. Zuniga, 372 P.3d 1052 (Colo. 2016); State v. Torgerson, 995 N.W.2d 164 (Minn. 2023); People v. Redmond, 2024 IL 129201 (Ill. 2024). Each treats marijuana odor as relevant but not independently sufficient for probable cause.

Legal Reasoning

The majority’s analysis proceeds in two principal stages: (1) probable cause and the automobile exception; and (2) reasonable suspicion and the plain-view doctrine.

1) Probable Cause Under the Automobile Exception

Probable cause remains a “fair probability” standard evaluated under the totality of the circumstances. Before legalization, marijuana odor was strongly probative of criminal activity because all possession/use/transportation was illegal.
Post-MRTMA, marijuana possession/use is generally lawful for adults within defined limits. The odor of marijuana may reflect lawful activity (e.g., prior legal use, possession of a legal amount) and is therefore no longer a sufficient standalone indicator that contraband or evidence of a crime will be found.
The Court aligns Michigan with jurisdictions that treat odor as one relevant circumstance that may, together with “something more,” satisfy probable cause. “Something more” might include, for example, observable impairment, visible smoke or active consumption in a prohibited place, corroborating admissions, age-based illegality, or other facts particularizing illegal use to a person/place/time.
Ybarra’s particularization principle looms large: legalization demands more precise grounding as to who used, when, where, and in a manner that is illegal.
Application: The prosecution’s motor-vehicle-search justification rested on odor alone. Because odor alone is insufficient, the automobile exception did not authorize the search.

2) Reasonable Suspicion and the Plain-View Doctrine

The trial court and Court of Appeals had demanded probable cause to justify the initial detention. The Supreme Court flagged this as error: a Terry stop requires reasonable suspicion, not probable cause. But the Court did not need to decide whether odor alone suffices for reasonable suspicion.
Assuming arguendo there was reasonable suspicion and a valid Terry stop, the question became whether the handgun was discovered in plain view. The plain-view doctrine allows warrantless seizure (not search) of items seen from a lawful vantage point if their incriminating character is immediately apparent.
On a limited record (bodycam footage and report excerpts), the trial court found as a fact that the handgun was discovered during a search, not in plain view. The Court of Appeals affirmed, and the Supreme Court found no clear error.
Because plain view is exclusively a seizure doctrine, it cannot justify the underlying search. A search requires probable cause—which odor alone did not supply. Thus, the prosecution’s alternative plain-view theory also failed.
Notably, the Court emphasized the prosecution’s burden and its failure to develop the record (declining an evidentiary hearing). This procedural posture mattered to the clear-error review and the outcome.

The Dissent’s Position (Justice Zahra)

Do not reach Kazmierczak: The dissent would have remanded because the lower courts misapplied the legal standard governing the initial seizure. The dissent argued that the handgun might have been seen in plain view during a lawful Terry stop, and that the trial court’s “search” finding was tainted by its legal error.
Reasonable suspicion from odor: Not every use is lawful—consumption in a passenger area or operation under the influence remain prohibited. Odor of burnt marijuana from an occupied car on a public street may itself create reasonable suspicion justifying a Terry stop and ordering occupants out for officer safety.
Additional factors: The record suggests other potential indicators (e.g., a furtive gesture, shaking hands) that might, combined with odor, have established probable cause. Because the lower courts applied the wrong threshold for the seizure, they improperly ignored those factors.
Kazmierczak’s continuing life: The dissent rejected a categorical repudiation, suggesting odor could still, in some scenarios, alone support probable cause for a vehicle search post-MRTMA (particularly where criminal prohibitions still apply).

Reconciling the Views

The majority retools probable cause doctrine to fit legalization: odor is probative but not dispositive. The dissent stresses the procedural misstep below and urges a narrower disposition that preserves at least some room for odor alone to constitute probable cause in the subset of situations where marijuana-related conduct remains criminal. Both opinions agree that Terry stops may be justified on less than probable cause; they part ways on whether this case required reaching Kazmierczak and on how to treat the trial court’s factual “search” finding.

Impact

On Law Enforcement Practices

No more “odor-only” car searches: Officers may no longer treat marijuana odor as a standalone gateway to search a vehicle under the automobile exception.
Document “something more”: Officers must articulate additional, particularized facts linking odor to unlawful conduct—e.g., visible smoke in a public place or passenger area, active consumption, objective indicators of impairment, admissions, underage occupants, or contraband in plain view.
Careful use of Terry stops: Odor may contribute to reasonable suspicion, but Armstrong does not decide whether odor alone suffices for reasonable suspicion. Officers should be prepared to justify stops with multiple factors. If conducting a stop, ensure any claimed plain-view observation is truly from a lawful vantage point and captured on body-worn cameras.
Record-building matters: The prosecution’s failure to request an evidentiary hearing proved pivotal. Detailed testimony and video establishing angles, visibility, and timing can make or break plain-view claims.

On Defense Strategy

Challenge odor-based searches: Move to suppress whenever the only asserted basis is marijuana odor. Probe whether any “additional facts” arose only after an illegal seizure.
Interrogate “plain view” rigorously: Demand proof of lawful vantage point, timing, and that the incriminating nature was immediately apparent. Emphasize Armstrong’s plain-view limitation as a seizure—not search—doctrine.
Exploit particularization: Argue Ybarra’s particularized-probable-cause requirement: odor does not specify who used, when, where, or unlawfully.

On Courts and Prosecutors

Standards hierarchy: Distinguish clearly between probable cause for searches and reasonable suspicion for Terry stops. Avoid conflating probable cause to search with the standard to initiate a stop (or with probable cause for civil infractions).
Good-faith reliance: Although the Court asked for briefing on Davis v. United States (good-faith reliance on binding precedent), the opinion does not reach or apply a good-faith exception. Whether Davis would shield pre-Armstrong odor-only searches in Michigan remains an open, case-dependent question.
Unresolved distinctions: The Court declined to distinguish between burnt and unburnt odor on this record. Future cases may test whether that matters for reasonable suspicion or probable cause.

Broader Legal Landscape

Alignment with other states: Michigan joins a growing consensus that odor is relevant but not dispositive post-legalization.
Home and person searches: While Armstrong concerns vehicles, its logic suggests caution elsewhere: odor alone is unlikely to constitute probable cause to search a home or person absent particularized facts.

Complex Concepts Simplified

Probable cause: Reasonable grounds to believe evidence of a crime will be found in a specific place. Requires a fair probability under the totality of circumstances.
Reasonable suspicion (Terry stop): A lower standard than probable cause. Requires specific, articulable facts suggesting criminal activity is afoot, permitting a brief detention to investigate.
Automobile exception: Allows warrantless searches of vehicles if officers have probable cause the vehicle contains contraband or evidence of a crime.
Plain-view doctrine: Permits warrantless seizure (not search) of items that officers lawfully see where the incriminating character is immediately apparent. It cannot justify entering or searching to find the item.
Particularization: Probable cause must be tied to the person/place searched, not general suspicion. Legalization reduces the inferential weight of odor unless linked to unlawful use by a particular person at a particular time and place.

Practical Guidance

For Law Enforcement

Do not search a vehicle based on marijuana odor alone.
Before searching, identify additional facts indicating illegal conduct (e.g., active smoking in a public place or vehicle passenger area; observable impairment; admissions; underage occupants; visible contraband).
When conducting a Terry stop, clearly articulate the specific, objective facts forming reasonable suspicion. Use body-worn cameras to capture vantage points and sequences.
If relying on plain view, ensure you are lawfully positioned, the object is visible without searching, and the incriminating nature is immediately apparent.
Develop the record. If a suppression motion is filed, request an evidentiary hearing to establish what officers saw, from where, and when.

For Prosecutors

Charge and argue with Armstrong’s framework in mind: odor plus “something more.” Avoid staking suppression fights on odor alone.
Anticipate defense “taint” arguments: if additional factors arose after an unlawful seizure, they may be excluded from the probable cause calculus.
Consider, where applicable, alternative bases (e.g., reasonable suspicion for a Terry stop; independent sources; inevitable discovery). Preserve good-faith arguments where supported by the record and timing.

For Defense Counsel

Pin the State to a clear timeline. If odor was the sole pre-seizure fact, argue Armstrong requires suppression of fruits of any search.
Scrutinize “plain view” rigorously: Was it truly seen without searching? Was the vantage point lawful? Did the camera capture it?
Leverage MRTMA’s text: permitted acts are “not grounds for search or inspection.” Use Ybarra particularization: odor does not identify the who/where/when of unlawful activity.

Unresolved Questions and Likely Future Litigation

Reasonable suspicion and odor alone: The Court assumed arguendo but did not decide whether marijuana odor alone suffices for reasonable suspicion. Expect litigation here.
Burnt vs. unburnt odor: The Court declined to draw a distinction on the record presented. Future cases may develop differing probative value.
Good-faith reliance: The opinion does not resolve whether Davis’s good-faith exception applies to odor-only searches conducted before Armstrong.
Probable cause in niche scenarios: The dissent suggests odor might still suffice alone in some contexts post-MRTMA (e.g., clear indicators of vehicle-related crime). The majority leaves that door only narrowly ajar by emphasizing totality and particularization.
Civil infractions and Terry: The Court flagged but did not decide whether reasonable suspicion of a civil infraction can justify a Terry stop. That question remains open in Michigan.

Conclusion

Armstrong is a watershed in Michigan search-and-seizure law under the legalization regime. It abrogates the bright-line Kazmierczak rule, holding that marijuana odor alone no longer establishes probable cause to search vehicles. Instead, odor is evidence that may contribute to probable cause when paired with particularized facts demonstrating illegal conduct by a specific person in a specific place at a specific time.

While the Court criticized the lower courts’ seizure analysis, it was unnecessary to decide whether odor alone creates reasonable suspicion; the trial court’s supported finding that the gun was discovered during a search—not in plain view—determined the outcome. The Court’s message is two-fold: legalization alters the inferences law enforcement may draw from odor alone, and the State bears the burden to build a robust record showing both lawful vantage and individualized illegality.

Going forward, Armstrong brings Michigan into line with other legalization jurisdictions, promotes careful, particularized policing, and provides clear guidance to courts: treat odor as one fact among many—not a proxy for criminality. The opinion’s unresolved issues (reasonable suspicion based on odor alone, good-faith reliance, and any distinction between burnt/unburnt odor) will likely shape the next wave of litigation at the intersection of cannabis reform and the Fourth Amendment.