A Missouri officer stopped Tyler McNeely after observing speeding and repeated lane crossings, saw signs of intoxication, and obtained a warrantless blood sample when McNeely refused a breath test. The Missouri courts suppressed the result, and the U.S. Supreme Court affirmed. The Court held that the natural dissipation of alcohol from the bloodstream does not create an exigency in every drunk-driving case. A compelled blood draw is a Fourth Amendment search, and the exigent-circumstances exception requires a case-specific assessment of whether officers had time to obtain a warrant. Alcohol dissipation is an important factor, but modern warrant procedures, available magistrates, transportation time, hospital conditions, and other practical circumstances may determine whether a warrant can be obtained before reliable evidence is lost. Because Missouri sought only a categorical rule and had not argued or developed the facts necessary to establish an exigency in this particular case, the Court did not decide whether the draw could have been reasonable under a properly individualized analysis. Justice Kennedy concurred in part. Chief Justice Roberts concurred in part and dissented in part, and Justice Thomas dissented. The judgment was affirmed.