Can Police Search a Car for the Smell of Weed in Missouri? It’s in the State Constitution

Missouri voters wrote the odor rule into the state constitution in 2022, and set it below probable cause, at reasonable suspicion. No Missouri appellate court has yet squared that text with a 1992 Supreme Court rule that odor alone is probable cause.

Can Police Search a Car for the Smell of Weed in Missouri? It’s in the State Constitution

Not on odor alone, outside an impaired-driving investigation. Under Mo. Const. art. XIV, § 2.10(10), the odor of marijuana or burnt marijuana, possession or suspected possession without evidence of an over-limit quantity, or multiple containers without such evidence “shall not individually or in combination with each other constitute reasonably articulable suspicion of a crime.” The exception is when you are investigating whether someone is operating a vehicle under the influence of marijuana.

Missouri: odor and the car — Article XIV: odor isn't reasonable suspicion of a crime — unless you're working an impaired driver. — Missouri: odor and the car — the statute, the controlling cases, and what still gets you into the car. The full breakdown lives inside StreetSense, offline.

What § 2.10(10) says

“No conduct permitted by this section shall constitute the basis for detention, search, or arrest; and except when law enforcement is investigating whether a person is operating a motor vehicle … while under the influence of marijuana, the odor of marijuana or burnt marijuana, the possession or suspicion of possession of marijuana without evidence of a quantity in excess of the lawful amount, or the possession of multiple containers of marijuana without evidence of quantity in excess of the lawful amount shall not individually or in combination with each other constitute reasonably articulable suspicion of a crime.”
Lawful marijuana is “not contraband nor subject to seizure.” In force since December 8, 2022.
Read it closely. The bar is reasonable suspicion, the lower standard, and you can’t stack odor with possession or extra containers to get there. The text states no exclusion remedy.

The impaired-driving exception

When you’re investigating operation of a vehicle under the influence of marijuana, the odor bar doesn’t apply.
Impairment still has to be proved. For a defendant 21 or older, a conviction requires evidence the person “was in fact under the influence of marijuana” and not solely the presence of THC or its metabolites (§ 2.3(1)(d)). DWI is RSMo 577.010; “intoxicated condition” includes a drug.

Villa-Perez — the rule that hasn't been tested

State v. Villa-Perez, 835 S.W.2d 897 (Mo. banc 1992): an officer who lawfully stops a vehicle and then smells marijuana, identified through training or experience, has probable cause; the smell “alone suffices for probable cause.” A Fourth Amendment case about raw marijuana at a truck’s cargo door, decided decades before legalization.
It has not been overruled, and we found no published Missouri appellate decision since Amendment 3 that decides whether legalization changes it. The constitution now speaks to the same facts at a lower standard. How Missouri courts will fit the two together hasn’t been decided.
Credibility is its own check: in State v. Wilson, 169 S.W.3d 870 (Mo. App. W.D. 2005), an odor claim contradicted by the dash video and the report was disbelieved, and suppression affirmed.

The person is different — Lee

State v. Lee, 498 S.W.3d 442 (Mo. App. W.D. 2016): “Nothing about having a single occupant of a vehicle where the smell of marijuana is present justifies an exception to the Fourth Amendment and allows a complete search of his person.”

How much is legal, and in the car

Adults 21 and over: three ounces or less of dried, unprocessed marijuana, “or its equivalent” (§ 2.10(1)(a)).
Up to twice the limit: civil, up to $250 on a first violation and $500 on a second; a misdemeanor with a fine up to $1,000 on a third (§ 2.10(6)). Under 21 with three ounces or less: civil, up to $100 and forfeiture, with a drug-education option (§ 2.10(5)). Smoking in a public place: civil, up to $100 (§ 2.10(4)).
Above twice the limit, RSMo 579.015 applies: more than 35 grams is a class D felony.
In the car: we found no RSMo offense for open cannabis or smoking in a vehicle. The constitution leaves room to regulate both (§ 2.3(1)(e), (f)); we found no statute that does.

The federal floor — and why it doesn't decide your case

Under the Fourth Amendment the automobile exception needs probable cause and nothing more (Maryland v. Dyson, 527 U.S. 465 (1999)), and marijuana is still illegal under federal law.
Missouri’s limit comes from its own constitution, at the reasonable-suspicion level. Villa-Perez itself is a Fourth Amendment decision.
That is the floor. Article XIV sits above it, and no Missouri appellate court has yet said how the two fit. Work to the constitution’s text and your prosecutor’s guidance.

How it plays out on the street

Interstate stop for a lane violation. Smell of burnt marijuana, adult driver, eyes clear, nothing in view. Under § 2.10(10) that odor isn’t reasonable suspicion of a crime — no extension and no search on it. Change one fact: a mile of weaving before the stop and thick, slow speech. Now you’re investigating whether the driver is operating under the influence, and the odor bar steps aside. Work the impairment and document it. Either way, the driver’s pockets are a separate question — Lee says odor doesn’t open the person.

Frequently asked questions

Can police search your car for the smell of weed in Missouri?

Not on odor alone outside an impaired-driving investigation. Mo. Const. art. XIV, § 2.10(10) provides that the odor of marijuana or burnt marijuana shall not, alone or combined with possession or multiple containers absent evidence of an over-limit quantity, constitute reasonably articulable suspicion of a crime. The exception is an investigation of driving under the influence of marijuana.

Is the smell of marijuana probable cause in Missouri?

State v. Villa-Perez (Mo. banc 1992) held that odor alone is probable cause, and it has not been overruled. Since December 8, 2022, the constitution says odor is not reasonable suspicion of a crime outside impaired-driving cases. No published appellate decision has said how the two fit.

How much weed can you have in your car in Missouri?

Adults 21 and over may possess three ounces or less of dried, unprocessed marijuana or its equivalent. Up to twice that amount is a civil infraction on a first or second violation.

Carry the rule, not the guesswork. StreetSense breaks down Missouri law like this — the statute, the limit, and the charge that actually sticks — verified against the code and available fully offline on shift. Start the free trial.

StreetSense is an educational reference for law enforcement, not legal advice. State law changes, and your department policy may be stricter than the statute. Always follow your state’s current rule and your agency’s policy.

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