Mitchell v. Wisconsin

In 2013, Gerald Mitchell was arrested for drunk driving in Wisconsin. After becoming unconscious at the police station, officers directed hospital staff to draw his blood without a warrant, relying on the state's implied consent law. The blood test revealed a blood alcohol concentration of 0.222%, and Mitchell was convicted. He challenged the warrantless blood draw as a violation of the Fourth Amendment. The Wisconsin Supreme Court upheld the conviction. The U.S. Supreme Court granted certiorari and, on June 27, 2019, issued a plurality opinion. The Court ruled that when a suspected drunk driver is unconscious and unable to take a breath test, the natural dissipation of alcohol in the blood creates an exigent circumstance that almost always permits a warrantless blood draw. The judgment was vacated and remanded for further proceedings consistent with the decision.

The U.S. Supreme Court reversed the Wisconsin Supreme Court in a 5-4 judgment. The plurality opinion, authored by Justice Alito, held that when a driver is unconscious and cannot perform a breath test, the exigent circumstances doctrine almost always justifies a warrantless blood draw due to the rapid metabolism of alcohol in the bloodstream. The case was remanded for lower courts to apply this framework.

The central dispute was whether the Fourth Amendment permits police to direct a warrantless blood draw from an unconscious motorist suspected of drunk driving, based on the exigent circumstances exception and state implied consent laws, or whether such a search constitutes an unreasonable bodily intrusion requiring a warrant.

The ruling significantly expanded police authority to conduct warrantless blood tests on unconscious DUI suspects, prioritizing the dissipation of alcohol as a near-automatic exigency. It provided clearer legal guidelines for law enforcement but raised serious privacy and bodily integrity concerns. Civil liberties advocates argued it weakened Fourth Amendment protections against invasive searches, while prosecutors and traffic safety groups praised it as a practical tool to combat impaired driving and close a loophole in DUI enforcement.