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Key Takeaways

• The Michigan Supreme Court’s 2024 decision in People v. Armstrong held that the odor of marijuana alone is not probable cause to search a vehicle.

• Michigan’s legalization framework (MMMA 2008, MRTMA 2018) means the smell of cannabis is consistent with lawful behavior, not criminal activity.

• People v. Koon (2013) established that medical marijuana patients cannot be prosecuted for OWI solely for THC presence, reinforcing the distinction between use and impairment.

• Michigan’s OWI statute, MCL 257.625, requires proof of actual impairment, not mere consumption.

• Armstrong significantly restricts warrantless vehicle searches and strengthens Fourth Amendment protections for Michigan drivers.

• Prosecutors now face heightened burdens to justify stops, searches, and arrests in cannabis‑related traffic cases.

• Defense attorneys can challenge searches, probable cause, officer observations, and toxicology evidence more aggressively post‑Armstrong.

Summary

The Michigan Supreme Court’s ruling in People v. Armstrong reshaped the legal landscape for cannabis‑related traffic stops by holding that the odor of marijuana, standing alone, does not establish probable cause. This decision reflects Michigan’s shift toward legalization under the MMMA and MRTMA, where cannabis possession and use are no longer inherently suspicious.

When combined with People v. Koon and Michigan’s OWI statute, Armstrong reinforces a central principle: lawful cannabis use cannot justify a search, arrest, or OWI charge without independent evidence of impairment or criminal activity. This article explains the ruling, its background, and its implications for Michigan drivers and defense strategy.

Background

Michigan’s cannabis laws have evolved dramatically over the past 15 years:

• 2008 – MMMA legalized medical marijuana.
• 2013 – People v. Koon held that registered patients cannot be prosecuted for OWI based solely on THC presence.
• 2018 – MRTMA legalized adult‑use marijuana statewide.
• 2024 – People v. Armstrong addressed how legalization affects probable cause during traffic stops.

Before legalization, the smell of marijuana was widely accepted as probable cause. After legalization, courts across the country began re‑evaluating whether odor still indicates criminal activity. Michigan joined that shift in Armstrong, recognizing that cannabis odor is now ambiguous — consistent with both legal and illegal conduct.

What the Research Shows

Although Armstrong is a legal decision, scientific research on cannabis impairment and odor detection provides important context:

• Studies from the National Institute of Justice (2021) show no correlation between THC levels and impairment.

• Field sobriety tests are unreliable indicators of cannabis intoxication.

• Michigan State Police have acknowledged that odor alone cannot determine impairment and that THC toxicology cannot reliably measure intoxication.

• Legal cannabis markets nationwide have forced courts to reconsider the evidentiary value of odor.

This scientific backdrop supports the Armstrong Court’s conclusion that odor is not a reliable indicator of criminal activity.

Legal Significance for DUI‑Marijuana Cases

Armstrong directly impacts Michigan OWI and search‑and‑seizure law:

• Odor ≠ probable cause for a vehicle search.

• Officers must articulate independent evidence of impairment or criminal activity.

• Under MCL 257.625, prosecutors must prove actual impairment, not mere THC presence.

• People v. Koon protects medical marijuana patients from OWI charges based solely on THC.

• Odor cannot justify expanding a traffic stop into a drug investigation.

• Evidence obtained from odor‑only searches may be suppressed under the Fourth Amendment.

Challenges for Prosecutors & Opportunities for the Defense

Prosecution Challenges

• Odor alone cannot justify a search, requiring officers to articulate additional facts.

• THC toxicology does not correlate with impairment, weakening OWI cases.

• SFSTs are unreliable for cannabis impairment, reducing evidentiary strength.

• Legal cannabis possession complicates claims of “suspicious behavior.”

• Armstrong increases suppression motions and limits warrantless searches.

• Officers must now distinguish between lawful and unlawful cannabis activity.

Defense Strategies

• Challenge the legality of the stop and search under Armstrong.

• Argue that odor is consistent with lawful MRTMA/MMMA conduct.

• Attack toxicology evidence as scientifically unreliable for impairment.

• Challenge SFSTs as invalid for cannabis detection.

• Use Koon to protect medical marijuana patients from THC‑only OWI charges.

• File motions to suppress evidence obtained from odor‑based searches.

In Closing

People v. Armstrong marks a major shift in Michigan’s approach to cannabis and constitutional rights. By rejecting odor‑only probable cause, the Court aligned Michigan law with modern legalization and scientific understanding. For defense attorneys, Armstrong provides powerful grounds to challenge searches, seizures, and OWI‑marijuana prosecutions statewide.

Sources & Authorities

• Transportation or possession of usable marihuana. MCL 750.474
• Michigan Regulation and Taxation of Marihuana Act scope and prohibitions (MRTMA). MCL 333.27954
• Municipal ordinances and transportation restrictions. MCL 333.27956
• Michigan OWI Statute – MCL 257.625
• People v Armstrong, — odor of marijuana and probable cause. Michigan Supreme Court
• People v Latz, Mich. Ct. App. (2016) — challenge to MCL 750.474 and interaction with medical‑use law. State Bar of Michigan

Michigan Resources

• Michigan Compiled Laws

• Michigan Court Rules

Komorn Law, founded in 1993, brings decades of seasoned experience to Michigan’s most complex criminal and regulatory matters, including the evolving cannabis framework from the MMMA to today’s MRTMA landscape. The firm represents clients facing controlled‑substance offenses, DUI and drug‑related driving charges, firearm violations, property crimes, resisting or obstructing, and the most serious allegations such as manslaughter and homicide. With a proven record in courts across Michigan and the federal system, Komorn Law delivers strategic, relentless advocacy when the stakes are highest. To work with a firm that truly refuses to back down.

Call  248-357-2550. 

Probable Cause and Marijuana Odor: Post ‑ Armstrong Search Strategies

This article analyzes the legal landscape for vehicle searches premised on the odor of marijuana, explains how recent Michigan decisions have changed probable‑cause analysis, and provides practical suppression and litigation strategies for defense counsel.

Summary

• Core principle: The odor of marijuana has historically been treated by many courts as a factor supporting probable cause to search a vehicle, but recent Michigan appellate and supreme‑court decisions have narrowed that rule.

• Practical effect: Odor alone is increasingly unlikely to sustain a warrantless vehicle search; courts now require corroborating indicia of criminal activity beyond smell.

• Defense focus: Suppression motions should attack odor‑based probable cause, emphasize statutory legalization and regulatory context, and develop factual records showing lack of exigency or other search exceptions.

Statutory and Doctrinal Context

• Statutory backdrop — Michigan’s regulatory framework legalizing adult possession and use of marijuana (and separate medical‑use statutes) changes the baseline expectations about what conduct is unlawful. When possession in certain amounts is lawful, the presence or smell of marijuana is less probative of criminal activity than it once was.

• Fourth Amendment framework — Vehicle searches without a warrant require probable cause under the automobile exception or another recognized exception (consent, exigency, inventory, search incident to arrest). Probable cause is a practical, common‑sense determination based on the totality of circumstances.

• Evidentiary shift — Courts increasingly treat odor as one factor among many; where odor is the only asserted basis for a search, suppression is often appropriate.

Typical Prosecution Theories Relying on Odor

• Probable cause to search for contraband — Officers claim that marijuana odor indicates contraband in the vehicle and therefore justifies a warrantless search.

• Probable cause to arrest for possession — Odor plus visible paraphernalia or admissions may be used to justify arrest and a subsequent search incident to arrest.

• Exigency arguments — Prosecutors sometimes argue that odor indicates imminent destruction of evidence, creating exigent circumstances that excuse a warrant.

Key Defense Strategies

1. Attack odor as insufficient alone

• Emphasize legalization context. Where state law permits possession within defined limits, odor is less probative of criminality; counsel should argue that smell alone cannot establish probable cause to search for contraband.

• Demand particularized facts. Require the prosecution to identify corroborating facts: visible containers, open packaging, driver or passenger admissions, suspicious movements, or other indicia of illegal activity.

2. Challenge exigency claims

• No automatic exigency. The mere possibility that a substance could be discarded does not create exigency; officers must show a real, articulable risk of imminent destruction that made obtaining a warrant impracticable.

• Time to obtain a warrant. Where officers had time and resources to secure the scene or obtain a warrant, exigency is weak. Document response times, availability of on‑call magistrates, and alternatives (securing the vehicle, detaining occupants while seeking a warrant).

3. Scrutinize officer observations and testimony

• Precision in testimony. Cross‑examine on the officer’s training, experience, and ability to distinguish odors (e.g., marijuana versus other odors).

• Chain of custody for odor claims. Where odor is asserted, probe whether the officer actually smelled it, where the odor originated, and whether other sources could explain the smell (air fresheners, legal hemp products, secondhand smoke).

4. Use statutory and regulatory context

• Possession thresholds. If the amount possessed is within lawful limits, argue that odor cannot support a search for contraband.

• Medical authorization. For medical‑use patients, develop records showing lawful possession and use; argue that medical authorization reduces the probative value of odor.

5. Preserve the record

• Evidentiary motions. File motions to compel body‑worn camera footage, dashcam video, and radio logs to test the officer’s account.

• Suppression motion timing. Move early to suppress evidence obtained from searches premised on odor; include requests for an evidentiary hearing where credibility and particularized facts are contested.

Sample Suppression Motion Themes and Language

Theme A — Odor Alone Insufficient

• Proposed language: “The odor of marijuana, without corroborating indicia of unlawful activity, does not establish probable cause to search the vehicle. Given statutory legalization and the absence of any visible contraband, admissions, or other suspicious conduct, the search was unreasonable under the Fourth Amendment.”

Theme B — No Exigency

• Proposed language: “The prosecution cannot meet its burden to show exigent circumstances. Officers had time and means to obtain a warrant or to secure the vehicle; the claimed risk of evidence destruction was speculative and insufficient to justify a warrantless intrusion.”

Theme C — Medical Use and Lawful Possession

• Proposed language: “Defendant possessed a lawful quantity of marijuana under state law and, where applicable, medical authorization. The odor therefore lacked the requisite nexus to criminal activity to support probable cause.”

Evidentiary and Discovery Checklist

• Body‑worn camera and dashcam footage for the entire encounter.

• Radio and CAD logs showing timing and communications.

• Officer training records on odor identification and drug recognition.

• Inventory of items seized and photographs of the vehicle interior.

• Statements from occupants and any recorded admissions.

• Records of magistrate availability and attempts to obtain a warrant.

Practical Advice for Clients and Law Enforcement Encounters

• For clients: Keep marijuana sealed and inaccessible while driving; avoid consuming in the vehicle; if stopped, remain calm and do not consent to searches.

• For counsel advising clients: Gather medical authorization and proof of lawful purchase/possession where applicable; preserve all electronic evidence immediately.

• For prosecutors and law enforcement: Document articulable facts beyond odor; obtain warrants when practicable; record the basis for exigency claims.

Litigation Roadmap

• Immediate discovery requests for all recordings and logs.
• File a suppression motion focused on the insufficiency of odor and lack of exigency.
• Request an evidentiary hearing to test officer credibility and the factual basis for the search.
• If suppression denied, preserve appellate issues by making clear objections and proffering alternative grounds for relief.

In Closing

Post‑Armstrong jurisprudence requires defense counsel to be proactive and precise: odor is no longer a talismanic basis for vehicle searches. Successful suppression practice will combine statutory context, rigorous factual development, and targeted cross‑examination to show that smell alone did not create probable cause or exigency. If you would like, I will prepare a fully cited memorandum that lists the controlling Michigan opinions, statutory text, and model suppression motions tailored to the most recent case law.

Sources & Authorities

• MCL 750.474 Transportation or possession of usable marihuana. Michigan Legislature
• MCL 333.27954 Michigan Regulation and Taxation of Marihuana Act scope and prohibitions. Michigan Legislature
• MCL 333.27956 Municipal ordinances and transportation restrictions. Michigan Legislature
• People v Armstrong, Michigan Supreme Court (2025) — odor of marijuana and probable cause. Justia Law
• People v Latz, Mich. Ct. App. (2016) — challenge to MCL 750.474 and interaction with medical‑use law. State Bar of Michigan

Michigan Resources

• Michigan Compiled Laws

• Michigan Court Rules

Komorn Law, founded in 1993, brings decades of seasoned experience to Michigan’s most complex criminal and regulatory matters, including the evolving cannabis framework from the MMMA to today’s MRTMA landscape. The firm represents clients facing controlled‑substance offenses, DUI and drug‑related driving charges, firearm violations, property crimes, resisting or obstructing, and the most serious allegations such as manslaughter and homicide. With a proven record in courts across Michigan and the federal system, Komorn Law delivers strategic, relentless advocacy when the stakes are highest. To work with a firm that truly refuses to back down.

Call  248-357-2550. 

This article is about what prosecutors and law enforcement commonly rely on during traffic stops involving cannabis in Michigan, Of course all cases and situations are not the same and evolve as they move forward.

This article analyzes the legal landscape for vehicle searches premised on the odor of marijuana, explains how recent Michigan decisions have changed probable‑cause analysis, and provides practical suppression and litigation strategies for defense counsel.

Overview of the Governing Statute

MCL 750.474 prohibits transporting or possessing usable marihuana in or upon a motor vehicle unless the cannabis is (a) enclosed in a case carried in the trunk or (b) enclosed in a case not readily accessible from the interior if the vehicle lacks a trunk. A violation is a misdemeanor punishable by up to 93 days’ imprisonment or a fine up to $500. The statute is the primary statutory basis prosecutors use when a traffic stop reveals cannabis in the passenger area.

What Prosecutors Look For During Traffic Stops

Prosecutors and officers evaluate a cluster of observable facts to determine whether to charge or seek a search. These factors fall into several categories.

1. Odor of marijuana

• Why it matters: Historically, the odor of marijuana has been treated as evidence that contraband may be present in a vehicle and thus as a basis for probable cause to search.

• Practical reality: Odor alone is often contested at suppression hearings; prosecutors pair odor with other indicia to strengthen probable cause.

2. Open or visible packaging

• Why it matters: Open containers, visible jars, loose plant material, or paraphernalia in plain view provide strong corroboration that unlawful possession or accessible cannabis exists.

• How prosecutors use it: Visible packaging converts a smell claim into a more concrete probable‑cause narrative.

3. Accessibility from the passenger compartment

• Why it matters: MCL 750.474 focuses on whether cannabis is readily accessible to occupants. Items in the trunk or in a secured, inaccessible case are less likely to support a transport charge.

4. Amount and packaging suggestive of distribution

• Why it matters: Large quantities, multiple small baggies, scales, vacuum sealers, or packaging materials shift the case from simple possession or transport to possession with intent to deliver or distribution, which carry greater penalties and investigative resources.

• How prosecutors proceed: Evidence of distribution often triggers additional counts and more aggressive search and seizure tactics.

5. Paraphernalia and indicia of recent use

• Why it matters: Pipes, bongs, rolling papers, burnt residue, or open containers in the passenger area support both possession and consumption allegations and can be used to justify searches or arrests.

• Related charges: Consumption in a vehicle and driving while impaired remain separate offenses that prosecutors pursue when impairment indicators exist.

6. Admissions and statements by occupants

• Why it matters: Voluntary admissions by drivers or passengers that they possess or recently used cannabis are highly probative and frequently cited in probable‑cause narratives.

• Defense note: The voluntariness and context of admissions are common suppression and credibility issues.

7. Vehicle and occupant behavior

• Why it matters: Nervousness, evasive answers, inconsistent stories, or attempts to hide items can be used to corroborate suspicion. Prosecutors combine behavioral observations with physical evidence to justify searches.

8. Associated criminal indicators

• Why it matters: Large amounts of cash, weapons, or prior criminal history may influence charging decisions and bail recommendations even if they do not by themselves establish probable cause for a search.

How Prosecutors Build a Probable‑Cause Narrative

Prosecutors typically assemble a narrative that links the observed facts to criminality:

• Initial observation: Officer detects odor or sees open packaging.
• Corroboration: Officer notes visible containers, paraphernalia, admissions, or packaging consistent with distribution.
• Search or arrest: Based on the totality of circumstances, the officer conducts a warrantless search under the automobile exception or makes an arrest and searches incident to arrest.
• Charging decision: Prosecutor evaluates seized items, quantities, and any admissions to determine appropriate charges (transport violation, possession, possession with intent to deliver, OWI, etc.).

Defense and Compliance Considerations

For defense counsel

• Attack odor‑only searches. Where odor is the primary or sole basis for a search, file suppression motions and demand an evidentiary hearing.

• Focus on accessibility. Under MCL 750.474, emphasize whether the cannabis was in the trunk or in a case not readily accessible.

• Challenge distribution inferences. Scrutinize packaging and quantity evidence; require proof of intent to deliver beyond mere quantity.

• Preserve the record. Seek body‑worn camera footage, dashcam video, CAD logs, and officer training records.

For drivers and the public

• Best practice: Keep cannabis sealed and in the trunk or in a locked, inaccessible case if the vehicle has no trunk.

• Do not consent to searches. Politely refuse consent to a vehicle search and request to speak with counsel if detained.

• Avoid consumption in vehicles. Do not consume cannabis while driving or in the passenger area of a vehicle on a public way.

For prosecutors and law enforcement

• Document corroborating facts. When relying on odor, document visible packaging, admissions, or other corroboration to withstand suppression challenges.

Tactical Checklist for Suppression Practice

• Request discovery immediately for all recordings and logs.

• File a suppression motion that (a) challenges odor as insufficient, (b) disputes exigency, and (c) contests the claimed accessibility of the cannabis.

• Subpoena officer training records and any drug‑recognition or odor‑identification certifications.

• Develop medical‑use evidence if the client is a registered medical patient to reduce the probative value of odor and possession.

• Preserve appellate issues by making contemporaneous objections and proffering alternative grounds for relief.

Sources & Authorities

• MCL 750.474 Transportation or possession of usable marihuana. Michigan Legislature
• MCL 333.27954 Michigan Regulation and Taxation of Marihuana Act scope and prohibitions. Michigan Legislature
• MCL 333.27956 Municipal ordinances and transportation restrictions. Michigan Legislature
• People v Armstrong, Michigan Supreme Court (2025) — odor of marijuana and probable cause. Justia Law
• People v Latz, Mich. Ct. App. (2016) — challenge to MCL 750.474 and interaction with medical‑use law. State Bar of Michigan

Michigan Resources

• Michigan Compiled Laws

• Michigan Court Rules

Komorn Law, founded in 1993, brings decades of seasoned experience to Michigan’s most complex criminal and regulatory matters, including the evolving cannabis framework from the MMMA to today’s MRTMA landscape. The firm represents clients facing controlled‑substance offenses, DUI and drug‑related driving charges, firearm violations, property crimes, resisting or obstructing, and the most serious allegations such as manslaughter and homicide. With a proven record in courts across Michigan and the federal system, Komorn Law delivers strategic, relentless advocacy when the stakes are highest. To work with a firm that truly refuses to back down.

Call  248-357-2550.