A state highway officer was performing his regular patrol at 2:00 a.m. when he stopped a driver for speeding.1 The routine traffic stop quickly turned into a DWI investigation when the driver, Tyler McNeely, exhibited the telltale signs of drunkenness: the smell of alcohol on his breath, bloodshot eyes, and slurred speech.2 The officer arrested McNeely after he failed standard field sobriety tests.3 When asked to submit to a DWI Breathalyzer test, McNeely refused, so the officer took him to a hospital and ordered a lab technician to draw McNeely’s blood for chemical testing.4 The test results revealed a blood-alcohol content of 0.154 percent—almost two times the legal limit of 0.08%.5
At trial, McNeely moved to suppress the blood test results, arguing that the forced withdrawal of his blood constituted an unreasonable search in violation of his Fourth Amendment rights.6 The State of Missouri relied on the 1966 U.S. Supreme Court decision Schmerber v. California7 in arguing that the quick dissipation of alcohol from McNeely’s body constituted exigent circumstances justifying the warrantless blood search.8 In Schmerber, the Supreme Court held that a nonconsensual, warrantless blood draw was permissible—under the specific exigencies present in that case—if based on probable cause and performed in a reasonable manner.9