The NCSL Blog


By Lisa Soronen

In Mitchell v. Wisconsin the U.S. Supreme Court held that generally when police officers have probable cause to believe an unconscious person has committed a drunk driving offense, warrantless blood draws are permissible. The State and Local Legal Center (SLLC) filed an amicus brief arguing for this result.

The Supreme CourtBy the time the police officer got Gerald Mitchell from his car to the hospital to take a blood test, he was unconscious. Mitchell’s blood alcohol content (BAC) about 90 minutes after his arrest was 0.222%.

Wisconsin and 28 other states allow warrantless blood draws of unconscious people where police officers have probable cause to suspect drunk driving.

Mitchell argued the police officer should have obtained a warrant before having his blood drawn. Per Supreme Court precedent, the Fourth Amendment’s ban on unreasonable searches generally requires police officers to obtain a warrant.

In Missouri v. McNeely (2013) the court held that the fact that blood-alcohol evidence is always dissipating due to “natural metabolic processes” does not generally mean the exigent circumstances exception applies and warrantless BAC tests are allowed. But in Schmerber v. California (1966) the court allowed a warrantless blood test of a drunk driver who had gotten into a car accident that “gave police other pressing duties,” because “ 'further delay’ caused by a warrant application really ‘would have threatened the destruction of evidence.’ ”

Reading these cases together, Justice Samuel Alito, writing for a plurality of the court, concluded an “exigency exists when (1) BAC evidence is dissipating and (2) some other factor creates pressing health, safety, or law enforcement needs that would take priority over a warrant application.”

According to the court, unconsciousness does not just create pressing needs; it is itself a medical emergency. “It means that the suspect will have to be rushed to the hospital or similar facility not just for the blood test itself but for urgent medical care.

"Police can reasonably anticipate that such a driver might require monitoring, positioning, and support on the way to the hospital; that his blood may be drawn anyway, for diagnostic purposes, immediately on arrival; and that immediate medical treatment could delay (or otherwise distort the results of) a blood draw conducted later, upon receipt of a warrant, thus reducing its evidentiary value.”

The reasoning of the plurality opinion mirrors the legal and policy arguments the SLLC made in its amicus brief. But instead of adopting a per se rule that no warrant is required when officers have probable cause an unconscious driver has driven drunk, the court created a rebuttable presumption.

“We do not rule out the possibility that in an unusual case a defendant would be able to show that his blood would not have been drawn if police had not been seeking BAC information, and that police could not have reasonably judged that a warrant application would interfere with other pressing needs or duties.”

Justice Clarence Thomas concurred writing separately that McNeely was wrongly decided. His position is that the exigent circumstances exception to the warrant requirement should apply in all drunk-driving cases because of the “imminent destruction of evidence.”

Lauren S. Kuley and Keith Bradley of Squire Patton Boggs wrote the SLLC brief in this case which the following organizations joined: National Conference of State Legislatures, International City/County Management Association, International Municipal Lawyers Association, and National District Attorneys Association.

Lisa Soronen is executive director of the State and Local Legal Center and a regular contributor to the NCSL Blog on judicial issues.

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This blog offers updates on the National Conference of State Legislatures' research and training, the latest on federalism and the state legislative institution, and posts about state legislators and legislative staff. The blog is edited by NCSL staff and written primarily by NCSL's experts on public policy and the state legislative institution.