On April 17, 2013, in Missouri v. McNeely, the Supreme Court of the United States (SCOTUS) rejected a per se rule allowing warrantless, non-consensual blood tests in DUI cases. The State of Missouri had argued that because blood tests dissipate at .015 to .020 an hour there should be an exception to the warrant requirement of the 4th Amendment. SCOTUS rejected this proposition in a 5 to 4 opinion. First, SCOTUS found that a blood test is a significant government intrusion even in the confines of a hospital under the supervision of trained medical staff. Interestingly, the Court implied that other Constitutional issues may arise for blood tests on the side of the road as in Arizona or Jails by Jail medical staff as in Georgia which weren’t specifically addressed.
Justice Sotomayor, joined by Justice Scalia, held that a per se rule allowing warrantless blood tests is unconstitutional but there may be circumstances in which a warrantless blood test would be allowed if for example the Officer was stuck investigating an accident and was not left with time to seek a warrant. Justice Roberts dissenting reasoned that a more reasoned approach would be allowing a warrantless blood test if the law enforcement made a reasonable determination that there was no time to obtain a warrant. Justice Thomas wrote a separate dissenting opinion approving an exception to the warrant requirement based solely on the issue of blood alcohol dissipation.