In DWI cases the police often make the determination that a blood test taken at a local hospital is needed. The question then becomes whether a warrant is necessary to secure such a test. Under the new US Supreme Court holding in Missouri v. McNeely, police who are interested in obtaining such blood tests will be required to secure a warrant from a judge to do so. 

There are some exceptions to the warrant requirement where, as the Court wrote, the “officer might reasonably have believed that he was confronted with an emergency in which the delay necessary to obtain a warrant, under the circumstances, threatened the destruction of evidence.”