The Fourth Amendment protects citizens from unreasonable searches and seizures by the government. Searches and seizures executed without a warrant are presumed unreasonable unless there is an established exception. The Supreme Court has found the act of drawing an individual’s blood (such as in a DUI investigation) to be a form of a seizure requiring a warrant, unless exigent circumstances make obtaining a warrant impractical. Courts evaluate the totality of the circumstances on a case-by-case basis to determine whether exigent circumstances justify a warrantless search. Exigent circumstances have been found to exist where the time needed to obtain a warrant would result in the destruction of evidence.
Last January, the United States Supreme Court decided in Missouri v. McNeely that in DUI investigations, the natural diminution of alcohol in a defendant’s bloodstream does not necessarily constitute an exigent circumstance sufficient to bypass the Fourth Amendment warrant requirement. Thus, if a DUI suspect does not consent to a blood test, the police will likely have to obtain a search warrant, issued only upon a showing of probable cause to believe the suspect is under the influence of a detectable drug. The Court noted, however, that the natural dissipation of alcohol may support a finding of exigency in a specific case, where other factors, such as the required procedures for obtaining a warrant and the availability of a judge, may affect the timeframe significantly.