A reasonable expectation of privacy is one of the most fundamental rights people hold in a free society. Accordingly, the Fourth Amendment prohibits warrantless searches, with few exceptions. Police officers in Wisconsin violated that right when they drew Gerald Mitchell’s blood while he was unconscious—to test his blood alcohol content after a drunk-driving arrest. The state has attempted to excuse the officers by citing an implied-consent statute, which provides that simply driving on state roads constitutes consent to such searches.
The right to privacy is not absolute; police are allowed to search for evidence of a crime. But in doing so, they must follow procedures that comport with the Constitution. Before police conduct a search, Johnson v. United States (1948) indicates that the evidence should be judged by “a neutral and detached magistrate instead of being judged by the officer engaged in the often competitive enterprise of ferreting out crime.” The Fourth Amendment contains a simple requirement for law enforcement that is an effective bulwark against unreasonable searches: get a warrant first.