Law enforcement can’t routinely skip obtaining a warrant before forcing uncooperative drivers suspected of being under the influence to take a blood test, the U.S. Supreme Court ruled this week.

The ruling arose from the case of Tyler McNeely, who was stopped by police in Missouri and exhibited signs of intoxication, including bloodshot eyes, slurred speech and the smell of alcohol on his breath.

After performing poorly on a field sobriety test, McNeely was arrested. He refused to take a breath test and to consent to a blood test. But police forced him to undergo a blood test, which revealed a blood alcohol level of 0.15 percent, almost twice the legal limit.

At his trial, a judge in Missouri’s Cape Girardeau County suppressed the blood-alcohol evidence, saying there had been no “exigent circumstances” that excused the police from obtaining a warrant before the test. “Warrantless intrusions of the body are not to be undertaken lightly,” the court said in an unsigned opinion, according to The New York Times.

The Missouri Supreme Court concluded last year that exigent circumstances did not preclude the need for a warrant. The case then wound up before the nation’s highest court, which affirmed the state court’s decision in a 5-4 ruling.

Justice Sonia Sotomayor, in an opinion joined by Justices Antonin Scalia, Ruth Bader Ginsburg, Elena Kagan and Anthony M. Kennedy, said many factors have to be considered in deciding whether a warrant is needed.

Those arguing against the need for a warrant argue that the time it takes to obtain one allows alcohol to dissipate from the bloodstream while a judge is being found. Justice Clarence Thomas alone took the position that the possible dissipation of alcohol is always more important than obtaining a warrant.

Justice Sotomayor, on the other hand, wrote that “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,” and she pointed out that warrants are easier to obtain than they used to be, thanks to technological developments.

-Noel Brinkerhoff

To Learn More:

Warrants Needed to Test Blood of Drunken Drivers (by Barbara Leonard, Courthouse News Services)

Supreme Court Ruling on Blood Draws Could Have Big Impact on Drunken Driving Cases (by Bruce Vielmetti, Milwaukee Journal Sentinel)

Court Says Police Need Warrant for Blood Test (by Adam Liptak, New York Times)

Missouri v. McNeely  (U.S. Supreme Court) (pdf)