Birchfield consolidated three cases. (1) Danny Birchfield (North Dakota) was arrested for driving under the influence (DUI) and refused a blood test after being warned that refusal was a crime; he was convicted of the refusal offense. (2) William Bernard (Minnesota) was arrested for suspected DUI and refused a breath test; under Minnesota law, refusal to submit to a breath test after arrest is a criminal offense, and he was charged accordingly. (3) Steven Beylund (North Dakota) consented to a blood draw after being told that refusal was a criminal offense; his license was revoked and the blood-test results were used against him in administrative proceedings. The petitioners argued that the Fourth Amendment prohibits states from criminalizing refusal to submit to warrantless breath or blood testing, and that such testing—if conducted without a warrant—cannot be justified as a search incident to arrest. The lower courts upheld the refusal statutes to varying degrees, leading to Supreme Court review on whether and to what extent breath and blood tests may be conducted without a warrant, and whether refusal to submit to such tests may be criminalized.
Whether the Fourth Amendment permits warrantless breath and blood tests as searches incident to a lawful DUI arrest, and whether states may criminalize refusal to submit to such warrantless tests.
Under the Fourth Amendment's search-incident-to-arrest doctrine, police may require a warrantless breath test incident to a lawful DUI arrest because the minimal intrusion on privacy is outweighed by the government's compelling interest in preventing and prosecuting drunk driving. However, warrantless blood tests are not categorically permissible as searches incident to arrest due to their significantly greater physical intrusion and the amount of personal information they can reveal; officers generally must obtain a warrant unless exigent circumstances exist. Implied-consent laws may impose civil penalties and evidentiary consequences for refusing chemical tests, but criminal penalties may not be imposed for refusing a warrantless blood draw; states may criminalize refusal of breath tests after a lawful arrest.
The Court held that (1) warrantless breath tests are permissible as searches incident to lawful DUI arrests; (2) warrantless blood tests are not permissible under the search-incident-to-arrest exception and generally require a warrant absent exigent circumstances; and (3) states may criminalize refusal to submit to a breath test but may not criminalize refusal to submit to a blood test. Applying these holdings, the Court affirmed Bernard's conviction for refusing a breath test, reversed Birchfield's conviction for refusing a blood test, and remanded Beylund's case to determine whether his consent to the blood draw was voluntary under the clarified legal framework.
Writing for the majority, Justice Alito applied the familiar balancing approach embedded in the search-incident-to-arrest doctrine, which permits certain categorical warrantless searches to protect officer safety and prevent destruction of evidence. The Court acknowledged the government's strong and legitimate interest in combating drunk driving: alcohol-impaired driving is dangerous, BAC evidence dissipates over time, and prompt testing is important to effective enforcement. But the costs to individual privacy vary depending on the testing method. Breath tests, the Court reasoned, are minimally intrusive: they require no piercing of the skin, are quick, carry little risk or discomfort, and reveal only one piece of information—BAC—without exposing broader, sensitive biological data. The Court analogized to prior search-incident precedents that allow categorical, limited intrusions incident to arrest and concluded breath tests fall comfortably within that doctrine. In contrast, blood draws are significantly more invasive, involving a needle puncture and extraction of biological material that can reveal a wealth of private information beyond BAC. Because of that heightened intrusion and privacy sensitivity, the Court refused to extend the categorical incident-to-arrest exception to blood draws. The Court emphasized that technological advances (such as streamlined electronic warrants) reduce the burden on officers seeking judicial authorization for a blood test, undermining arguments that a categorical exception is necessary. It reaffirmed Missouri v. McNeely's rule that the natural dissipation of alcohol does not create a per se exigency; instead, exigency must be assessed case-by-case. Turning to consent, the Court recognized the longstanding legitimacy of implied-consent regimes tied to the privilege of driving, but limited their scope: such statutes can impose civil penalties and evidentiary consequences for refusal, yet cannot convert refusal of a constitutionally protected choice (a warrantless blood draw) into a criminal offense. Applying these principles, the Court concluded that Minnesota could criminalize refusal of breath tests post-arrest, while North Dakota could not criminalize refusal of warrantless blood tests, and it remanded Beylund's case to reassess the voluntariness of consent given the erroneous threat of criminal penalties. Separate opinions underscored the stakes. Justice Thomas would have allowed both breath and blood tests under the search-incident doctrine. Justice Sotomayor, joined by Justice Ginsburg in substantial part, would have required warrants for both breath and blood tests, rejecting the categorical incident-to-arrest approach in this context.
Birchfield squarely delineates the constitutional boundary between breath and blood testing in DUI enforcement, providing clear guidance to police, legislatures, and courts. It preserves a powerful, categorical tool—warrantless breath testing incident to arrest—while insisting on warrants or valid exceptions for more invasive blood draws. The decision also cabins the reach of implied-consent laws, permitting civil and evidentiary penalties but foreclosing criminal penalties for refusing a warrantless blood test. For law students, Birchfield is a foundational case on how the Court balances government interests and privacy under the search-incident doctrine, harmonizes that doctrine with exigent-circumstances and consent analyses, and applies McNeely's no-per-se-exigency rule.
Birchfield v. North Dakota carefully balances highway safety and constitutional privacy. By categorically authorizing warrantless breath tests incident to arrest but requiring warrants for blood draws absent exigency, the Court delivers a nuanced framework that promotes effective DUI enforcement without sacrificing core Fourth Amendment protections.