Tyler McNeely was pulled over late at night after a state trooper observed him driving erratically. When McNeely refused to take a Breathalyzer test, the officer drove him to a local hospital and ordered blood drawn for an alcohol test. The officer did not seek a warrant, even though he had done so in previous cases. The state of Missouri contended that because alcohol naturally dissipates in the bloodstream, each passing moment means valuable evidence is being lost, and so a warrant is never required for a blood draw.
The Supreme Court disagreed, noting that in most circumstances there is adequate time to get a warrant. Justice Sonia Sotomayor, writing for the majority, said that in the modern world of technology, police can often obtain a warrant quickly by using their cellphones or by email, and that in most jurisdictions a magistrate is available at all hours to grant a warrant request.