By Anna E. Bodi, ACLR Featured Online Contributor

It is just before midnight. A state trooper notices a car with a defective taillight cruising down a state highway and stops the vehicle. Upon approaching the driver’s door, the trooper notices a strong scent of marijuana. After some brief questioning, the trooper searches the vehicle based on the smell and the likelihood of finding marijuana in the vehicle. The search uncovers a glass pipe, two lighters, and a substance that appears to be marijuana; the driver is ultimately arrested and charged with misdemeanor possession of marijuana and drug paraphernalia. Now, imagine a small change. Imagine this scenario occurs in a state where possession of marijuana has been decriminalized or even legalized. The smell of marijuana could not provide the same probable cause for a warrantless search if it no longer indicates criminal activity. If having marijuana in the car would be a perfectly legal act under state law, how can such a search be legal?

States that have legalized or decriminalized possession of marijuana may soon be dealing with this very issue. Such states (which now include Colorado, Washington, Oregon, and Alaska1) should move toward a more protective Fourth Amendment standard when it comes to the “plain smell” of marijuana. The odor of marijuana alone should no longer be sufficient probable cause to justify a warrantless search of a vehicle, let alone a house, where privacy expectations are heightened. Legalization or decriminalization will necessarily change what constitutes probable cause for searches based on smell, safeguarding the constitutional rights of citizens.

Though the concept of plain smell, a variation of the plain sight principle, might seem familiar, the United States Supreme Court has never explicitly extended plain sight to cover odors, and has never adopted plain smell as a basis for a warrantless search. The Supreme Court has addressed the issue in several cases, dating back decades. In Taylor v. United States, a case decided during the Prohibition Era, the Court held that the smell of whiskey alone was not sufficient to allow police officers to search the garage of a house without a warrant.2 However, some assert that because the expectation of privacy is higher in a home than in other places, Taylor should not be considered a condemnation of plain smell in all circumstances.3 In 1948, the Court came to a similar conclusion in Johnson v. United States, but denied that Taylor stood for the notion that “odors cannot be evidence sufficient to constitute probable grounds for any search.”4 The Johnson Court clarified the prior decision: “That decision held only that odors alone do not authorize a search without a warrant.”5 The Court went on to explain that an odor could be a sufficient basis to justify the issuance of a search warrant.6

More recently, the Court has ducked the issue altogether, as in United States v. Johns: “The Court of Appeals rejected the Government’s contentions that the plain odor of marihuana emanating from the packages made a warrant unnecessary and that respondents Johns and Hearron lacked standing to challenge the search of the packages. Neither of these issues is before this Court.”7 In Florida v. Jardines, a case involving a warrantless “dog-sniff” on the porch of a home, the Court acknowledged the existence of plain smell, but only in analogizing a drug detection dog and plain smell to binoculars and plain view.8

Despite the Supreme Court’s failure to make a definite determination on the legality of warrantless searches based on plain smell, lower federal courts have generally embraced the principle and practice.9 State courts have largely followed suit.10 However, Massachusetts distinguished itself from this judicial consensus after possession of small amounts of marijuana was decriminalized in the state.

Massachusetts courts have found that the odor of marijuana alone is not sufficient probable cause to justify a warrantless search.11 In 2011, the Massachusetts Supreme Court found that in light of the state statute changing the status of possessing an ounce or less of marijuana from a crime to a civil violation, “without at least some other additional fact to bolster a reasonable suspicion of actual criminal activity, the odor of burnt marijuana alone cannot reasonably provide suspicion of criminal activity to justify an exit order.”12 In that case, the defendants had been ordered to exit the car so that the officers could conduct a warrantless search of the vehicle.13 In two cases decided on the same day in 2014, the Massachusetts Supreme Court extended its decision in Cruz to the odor of unburnt marijuana, finding that the odor of unburnt marijuana emanating from the defendants’ vehicles, without more, did not provide probable cause for police officers to search the vehicles.14

The Craan court addressed head on the conflict between decriminalization of marijuana under the state law and the unchanged federal prohibition on marijuana possession. It found that the state officers could not assert that the search based on the odor of marijuana was reasonable because they had sufficient probable cause that the vehicle contained evidence of a federal crime.15 The court noted that the stop and search was not part of a joint federal-state investigation, and that the U.S. Department of Justice has repeatedly indicated a “lessened interest” in prosecuting individuals for possession of marijuana.16 The court therefore held that where “State law expressly has decriminalized certain conduct, there is no extant joint investigation, and the Federal government has indicated that it will not prosecute certain conduct, the fact that such conduct is technically subject to a federal prohibition does not provide an independent justification for a warrantless search.”17

Courts in states that have recently gone even further than Massachusetts and legalized marijuana, such as Washington, Oregon, Alaska, and Colorado, should take a cue from Massachusetts. The smell of a legal or decriminalized substance should no longer provide probable cause for a warrantless search. Using the rationale from Massachusetts, warrantless searches for contraband when no specific facts suggest criminality are unreasonable. The legalization of marijuana eliminates criminal and civil consequences associated with possession of marijuana (though the amount may be limited). Therefore, the odor of marijuana can no longer constitute “a specific fact suggesting criminality” and provide “probable cause to believe that a vehicle contains a criminal amount of contraband or specific evidence of a crime” justifying a warrantless search of the vehicle.”18

While citizens in these states may “breathe a little easier,” it may still take some time before the law of probable cause changes more broadly. States where marijuana remains illegal may see things differently from the Massachusetts court. At the federal level, consistent with the views of the lower federal courts, the odor of marijuana could still provide the basis for a search as part of a federal law enforcement effort. Additionally, denying the opportunity for police to search a vehicle without a warrant is not a license to drive under the influence. But that latter point, about just what constitutes driving under the influence when marijuana is legal, is a topic for another time and another blog post.