579 U.S. 438 (2016) (U.S. Supreme Court)
Birchfield v. North Dakota is a landmark Fourth Amendment decision that draws a bright-line distinction between breath and blood tests administered to suspected drunk drivers after arrest.
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.
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.