WASHINGTON - Police officers generally must try to get a warrant before forcing uncooperative drunken driving suspects to submit to a blood test, the Supreme Court ruled Wednesday.
The natural dissipation of alcohol in a person's bloodstream does not justify an exception to the general constitutional requirements of a warrant, Justice Sonia Sotomayor wrote for the majority.
She said such emergencies must be determined by the circumstances in a case-by-case examination and rejected the notion that officers face a "now or never" situation in obtaining blood-alcohol tests.
"In those drunk-driving investigations where police officers can reasonably obtain a warrant before a blood sample can be drawn without significantly undermining the efficacy of the search, the Fourth Amendment mandates that they do so," wrote Sotomayor.
She was joined in her main holding by Justices Antonin Scalia, Anthony Kennedy, Ruth Bader Ginsburg and Elena Kagan.
Chief Justice John Roberts agreed with the outcome of the case, which affirmed a decision from the Missouri Supreme Court, but criticized the vagueness of the majority's test.
"A police officer reading this court's opinion would have no idea - no idea - what the Fourth Amendment requires of him, once he decides to obtain a blood sample from a drunk driving suspect who has refused a breathalyzer test," wrote Roberts, who was joined by Justices Stephen Breyer and Samuel Alito Jr.
Strong words aside, Roberts' proposed rule differed mostly by degree.
"If there is time to secure a warrant before blood can be drawn, the police must seek one," Roberts wrote. "If an officer could reasonably conclude that there is not sufficient time to seek and receive a warrant, or he applies for one but does not receive a response before blood can be drawn, a warrantless blood draw may ensue."
Justice Clarence Thomas was the lone justice agreeing with Missouri and the U.S. government that the metabolization of alcohol in the blood created the kind of emergency that does not require a warrant.