Does the Fourth Amendment permit warrantless breath tests, but not warrantless blood tests, as searches incident to a lawful arrest for drunk driving, such that a state may criminalize refusal to take a breath test but not a blood test?

All three petitioners were arrested on suspicion of drunk driving in North Dakota or Minnesota, states that make it a crime to refuse a blood-alcohol concentration (BAC) test after a lawful arrest. Danny Birchfield drove his car into a ditch, failed field sobriety tests, and registered a 0.254% BAC on a roadside breath screening. After the arresting trooper advised him that refusing a blood test was a crime, he refused and pleaded guilty to a misdemeanor refusal charge on a conditional basis, preserving his Fourth Amendment challenge. William Robert Bernard, Jr., was found near a truck stuck in a river at a boat launch, smelled of alcohol, and was arrested. At the police station he was read Minnesota's implied consent advisory, refused a breath test, and was charged with first-degree test refusal because of four prior impaired-driving convictions. Steve Michael Beylund nearly hit a stop sign while driving, struggled to keep his balance, and was arrested. At a hospital he was told that refusing a test was itself a crime, agreed to a blood draw, and registered a BAC of 0.250%, more than three times the legal limit. His license was suspended for two years.

Birchfield pleaded guilty to a misdemeanor violation of North Dakota's refusal statute, reserving his Fourth Amendment argument. The State District Court rejected the argument and sentenced him, and the North Dakota Supreme Court affirmed. Bernard was charged in Minnesota with first-degree test refusal. The Minnesota District Court dismissed the charges on the ground that the warrantless breath test was not permitted by the Fourth Amendment. The Minnesota Court of Appeals reversed, and the Minnesota Supreme Court affirmed that reversal, relying on the search-incident-to-arrest doctrine. Two justices dissented. Beylund's license was suspended after an administrative hearing. He appealed to a North Dakota District Court, arguing that his consent to the blood test was coerced by the officer's warning that refusal was a crime. The District Court rejected the argument, and the North Dakota Supreme Court affirmed, relying on its Birchfield decision upholding the refusal penalties. The U.S. Supreme Court granted certiorari in all three cases and consolidated them for argument.

(Alito, J.)

Yes. The Fourth Amendment permits warrantless breath tests as searches incident to a lawful drunk-driving arrest, so a state may criminalize refusal of a breath test. It does not permit warrantless blood tests incident to arrest, so a state may not criminalize refusal of a blood test.

Taking blood or administering a breath test is a Fourth Amendment search. Under Riley v. California, whether a search falls within the search-incident-to-arrest exception, which applies categorically, depends on the degree to which it intrudes on individual privacy and the degree to which it is needed to promote legitimate governmental interests. Because the founding era gives no definitive guidance on these tests, this balancing governs.

Breath tests intrude only slightly. They require no piercing of the skin, demand only that the arrestee blow into a mouthpiece, are no more intrusive than a cheek swab (Maryland v. King) or fingernail scraping (Cupp v. Murphy), reveal only a BAC reading, retain no sample, and add little to the embarrassment inherent in an arrest. Blood tests pierce the skin, extract part of the body, and yield a preservable sample containing other information, so they are significantly more intrusive.

The governmental interest in BAC testing is great. States have a compelling interest in highway safety and in deterring drunk driving, and criminal refusal penalties give the most dangerous offenders an incentive to cooperate. A warrant requirement is rejected because search-incident-to-arrest rules are categorical (United States v. Robinson), unlike the case-by-case exigency exception in Missouri v. McNeely. A warrant for every BAC test would burden the courts, given over one million drunk-driving arrests a year, and would offer little benefit because probable cause facts are similar from case to case and the scope is always a BAC test. Alternatives such as checkpoints and ignition interlocks are poor substitutes. Nothing limits the exception to active destruction of evidence; it covers evidence loss generally, including the natural metabolization of alcohol.

Blood tests are unjustified because breath tests adequately serve law enforcement interests. Police may seek a warrant or invoke exigent circumstances when a blood test is needed. Implied consent also cannot justify criminal penalties for refusing a blood test, because there must be a limit to the consequences to which motorists are deemed to consent by driving.

Birchfield's conviction is reversed, Bernard's is affirmed, and Beylund's case is vacated and remanded for the state court to reevaluate the voluntariness of his consent given the officer's partly inaccurate advisory.

Concurring in part and dissenting in part (Sotomayor, J., joined by Ginsburg, J.) Birchfield and Beylund are correctly decided, but Bernard is not. The warrant requirement is the usual safeguard, and a categorical exception is justified only if obtaining a warrant would frustrate the governmental purpose behind the search. It would not here. Once a drunk driver is arrested he poses no immediate threat. Evidentiary breath tests are conducted at a station 45 minutes to two hours after arrest, after a mandatory observation period, a window to call a lawyer, and machine warm-up, and the States allow a two-hour testing window, which leaves ample time to obtain a warrant, including telephonically. The burden is small: North Dakota and Minnesota judges would each issue under two extra warrants a week, fewer than one if refusal rates are doubled. Convenience in gathering evidence cannot justify a warrant exception. Exigent circumstances, applied case by case, adequately address any true emergency, as Riley and McNeely reasoned. The search-incident-to-arrest exception, built for immediate arrest-related dangers, is ill suited to breath tests conducted well after arrest and only in drunk-driving cases. The majority responds that the search-incident-to-arrest doctrine has always served investigative ends and that no authority bars it from applying merely because a narrower exception might also apply.

Concurring in the judgment in part and dissenting in part (Thomas, J.) The line between breath and blood tests is arbitrary and departs from Robinson's categorical rule, producing case-by-case balancing that is unpredictable for police and courts. The better approach is the per se rule from his McNeely dissent: the natural metabolization of alcohol creates an exigency once police have probable cause that a driver is drunk, so both warrantless breath and blood tests are constitutional under the exigent-circumstances exception. The majority treats the distinction between active destruction of evidence and natural dissipation as meaningless for searches incident to arrest, and that same logic should apply to exigent-circumstances searches.