States that made it a crime for drivers suspected of drunken driving to refuse alcohol tests now will find it more difficult to obtain evidence in some circumstances.

The U.S. Supreme Court ruled that police must get a search warrant before forcing drivers to take a blood alcohol test.  Breath tests done by blowing into a machine were considered less intrusive and therefore no warrant is required.

There were three cases involving drivers who challenged what are known as “implied consent laws.”  The cases, brought in Minnesota and North Dakota, claimed that the implied consent law violated the Constitution’s ban on unreasonable searches and seizures. The decisions had been upheld in each State’s supreme court.

The Court’s ruling affects laws in eleven states that had imposed additional criminal penalties for suspects who refused drunk driving tests.  Drivers in all states can have their licenses revoked for refusing.  Besides Minnesota and North Dakota, additional states that criminalize a driver’s refusal to take alcohol blood or breath tests are Louisiana, Tennessee, Alaska, Florida, Indiana, Vermont, Virginia, Nebraska, and Rhode Island.

Justice Samuel Alito, writing for the majority, said breath tests do not implicate “significant privacy concerns.” Alito went on to say that unlike blood tests that extract blood, the breathing into a breathalyzer doesn’t pierce the skin or leave a biological sample in the government’s possession.

The challengers argued before the high court that warrantless searches should be allowed only in “extraordinary circumstances,” and that privacy rights should apply during routine drunk driving stops because they are ordinary law enforcement functions.

Justice Clarence Thomas dissented, saying he would have found both tests constitutional. Whereas Justices Sonia Sotomayor and Ruth Bader Ginsburg said they would have gone further and required search warrants for both blood alcohol and breath tests. 

State officials, on the other hand, argued that the testing laws were a legitimate condition on the privilege of using state roads. 

State prosecutors stated that forcing police to get a warrant every time a driver refused a test would be too burdensome.  They pointed out that in some rural areas only one judge might be on call late at night or on weekends.  They further argued that even if police get a warrant, a driver can still refuse to take an alcohol test and face lesser charges for obstruction.  Some justices stated in oral arguments that that magistrates are easily reachable over the phone in just a few minutes to get a warrant.

Several civil liberties groups weighed in on the debate saying that states can’t criminalize the assertion of a constitutional right, whereas Mothers Against Drunk Driving contended that the laws were needed for public safety.