Missouri v. McNeely

“To determine whether a law enforcement officer faced an emergency that justified acting without a warrant, this Court looks to the totality of circumstances.” In doing so, the Court rejected a standard rule that would have excused the government from the warrant requirement in all drunk driving cases. The Court held that “while the natural dissipation of alcohol in the blood may support a finding of exigency in a specific case, as it did in Schmerber, it does not do so categorically. Whether a warrantless blood test of a drunk-driving suspect is reasonable must be determined case by case based on the totality of the circumstances.” Exceptions may be granted where the government can demonstrate that exigent circumstances exist in a particular case because a warrant could not have been obtained within a reasonable amount of time. The government made no such showing here.