The United States Supreme Court has ruled that the fact that alcohol dissipates from the bloodstream over time does not by itself give the police the right to draw blood without a warrant in drunken-driving investigations. Lyle Denniston in the SCOTUS blog put it succinctly, “A police officer out on patrol who stops a driver who seems to be drunk may not have read through four new Supreme Court opinions and counted the Justices’ votes accurately, but that officer would probably do the sensible thing by getting a warrant before having the driver’s blood tested without consent.” Justice Sotomayor announced the judgment of the Court and delivered the opinion of the Court in large measure in Missouri v. McNeely.  Justice Kennedy issued an opinion concurring in part. Chief Justice Roberts issued an opinion concurring in part and dissenting in part, in which Justices Breyer and Alito joined. Justice Thomas issued a dissenting opinion. You can access the oral argument via this link.