In two unanimous rulings, the state’s highest court said they had already decided in 2011 that the odor of smoked marijuana by itself did not provide police with probable cause to stop people on the street or search the vehicles people are riding in.

The Supreme Judicial Court Wednesday said that because voters decriminalized small amounts of marijuana in 2008, police officers in Massachusetts can no longer rely on the odor of unburnt marijuana to justify searching a person’s car.

The court said in its 2011 ruling that it would be legally inconsistent to allow police to make warrantless searches after they smell burning marijuana when citizens had decided through a statewide referendum question that law enforcement should “focus their attention elsewhere.’’


The court said Wednesday it was now extending the same reasoning to cases where the owner has not yet started smoking it. Marijuana, the court acknowledged, generates a pungent aroma, but an odor by itself does not allow police to determine whether a person has more than an ounce with them. Possession of an ounce or less of marijuana is not a crime.

“The 2008 initiative decriminalized possession of one ounce or less of marijuana under State law, and accordingly removed police authority to arrest individuals for civil violations,’’ Justice Barbara Lenk wrote for the unanimous court.

“We have held that the odor of burnt marijuana alone cannot support probable cause to search a vehicle without a warrant ... [now] we hold that such odor [of unburnt marijuana], standing alone, does not provide probable cause to search an automobile.’’

TECH LAB: Paying the price for free software

The court established the new legal standard in the case of Matthew W. Overmyer, who was arrested in Pittsfield by police investigating a car crash. Responding officers noticed what the SJC called “a very strong odor of unburnt marijuana.’’


Police found one bag of marijuana in the glovebox of Overmyer’s car, and a backpack holding even more, leading police to charge him with possession of marijuana with intent to distribute.

The court said police could not use their noses alone to arrest Overmyer, but might have had another legally approved basis for searching his car. They ordered the case back to the district court for more proceedings.

RELATED: The inside story of MIT and Aaron Swartz

In the second ruling, the SJC threw out criminal charges of illegal possession of ammunition and illegal possession of prescription drugs filed against Anthony Craan. Craan was stopped in Dorchester in 2010 by State Police operating a sobriety checkpoint on Gallivan Boulevard.

A trooper ordered Craan to pull over based on the odor of unburnt marijuana and then found three Ecstasy pills and .38-caliber ammunition after searching Craan’s car. Craan was not arrested at the time, but summonsed into Boston Municipal Court.

The SJC said police had no legal basis to search Craan’s car and ordered the evidence against him suppressed.

The court also rejected the argument from law enforcement that local police can use the odor of marijuana to stop someone because possession of marijuana is still an offense under federal law.

“The fact that such conduct is technically subject to a Federal prohibition does not provide an independent justification for a warrantless search,’’ Lenk wrote.


Related:

• Movie review: Aaron Swartz, ‘The Internet’s Own Boy’

• The inside story of MIT and Aaron Swartz

• Reddit part of debate over digital media after bombings posts

• How privacy became an American value

• Editorial cartoon: Legalize it! Then corporatize it!

• Ideas: This is your language on cannabis

John R. Ellement can be reached at ellement@globe.com. Follow him on Twitter @JREbosglobe.