In a 5-3 decision, the court ruled that while officers can require a warrant-less breath test, and states can require drivers arrested for being intoxicated to submit to one, that blood tests are too invasive and require a warrant.
Justice Samuel Alito wrote the opinion joined by Chief Justice John Roberts and Justices Anthony Kennedy, Stephen Breyer and Elena Kagan.
Because there were three separate cases before the court, each defendant had a different result. The court held that Danny Birchfield, who was prosecuted in North Dakota for refusing a blood test, should have his conviction overturned.
William Bernard Jr., prosecuted in Minnesota for refusing a breath test, had his conviction upheld.
In the third case, Steve Beylund consented to a blood test under threat of prosecution in North Dakota; his case was sent back to lower courts in light of the court's ruling that warrant-less blood tests can't be mandated under threat of penalty.
"Because breath tests are significantly less intrusive than blood tests and in most cases amply serve law enforcement interests, we conclude that a breath test, but not a blood test, may be administered as a search incident to a lawful arrest for drunk driving," Alito wrote. "As in all cases involving reasonable searches incident to arrest, a warrant is not needed in this situation."
There were two partial dissents. Justices Sonia Sotomayor wrote for herself and Justice Ruth Bader Ginsburg, who argued that warrants should be required in all cases. Justice Clarence Thomas wrote a partial dissent arguing that warrants should be required in neither case.
Sotomayor had harsh words for the court's willingness to not require warrants and the argument that it was a matter of not overwhelming judges.
"This court has never said that mere convenience in gathering evidence justifies an exception to the warrant requirement," Sotomayor wrote. "I fear that if the court continues down this road, the Fourth Amendment's warrant requirement will become nothing more than a suggestion."
Thirteen states criminalize a driver's refusal to submit to a warrantless chemical test of his or her blood, breath, or urine to detect the presence of alcohol in order to deter drunk drivers.
In court papers, North Dakota noted that between 2005 and 2014, 112,998 people were killed in alcohol impaired driving crashes in the United States.
"North Dakota has suffered more than its share of this carnage," the state's attorneys argued. The North Dakota law was passed after Wyatt Klein, who had consumed seven or eight beers and three shots of tequila, struck the car of Aaron and Allison Deutscher, instantly killing them and their daughter. Klein had a history of drunk driving violations.
Like many states, North Dakota relies upon "implied consent" laws, meaning that in return to access to public road, drivers consent to taking a chemical test upon arrest for drunk driving. North Dakota and other states go further saying that if the driver is stopped and denies his consent, he is subject to criminal penalties.
The court's ruling invalidated the idea of so-called implied consent when criminal penalties are levied for refusing to submit to a blood test.
"There must be a limit to the consequences to which motorists may be deemed to have consented by virtue of a decision to drive on public roads," Alito wrote.