Mitchell was arrested for DUI. He subsequently became unconscious. Since he could not submit to a breath test, the arresting officer could not obtain his consent to a blood test, and he needed medical attention, the officer took him to a hospital for treatment and to have his blood drawn without a warrant. The State conceded that exigent circumstances were not present to justify the warrantless blood draw. Instead, the State argued that the blood draw was justified under the State’s implied consent law, that an unconscious suspect is deemed to not have withdrawn consent to a test where the officer has probable cause to believe the driver is impaired by alcohol. In Mitchell v. Wisconsin, although the Supreme Court accepted review based on the implied consent issue, a plurality of four justices held that dealing with an unconscious driver will almost always involve exigent circumstances.
The court said:
When police have probable cause to believe a person has committed a drunk-driving offense and the driver’s unconsciousness or stupor requires him to be taken to the hospital or similar facility before police have a reasonable opportunity to administer a standard evidentiary breath test, they may almost always order a warrantless blood test to measure the driver’s BAC without offending the Fourth Amendment. 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. Because Mitchell did not have a chance to attempt to make that showing, a remand for that purpose is necessary. 
Unusually, the Supreme Court did not address the question upon which certiorari was granted – whether an implied consent statute can supply consent that passes muster under the Fourth Amendment to a blood test. This leaves open the question of whether a compelled warrantless blood test in a case involving death or life-threatening injury pursuant to Transp. § 16-205.1(c) complies with the Fourth Amendment.
 Mitchell v. Wisconsin, 2019 WL 2619471, at *9 (U.S. June 27, 2019).