On Wednesday, U.S. Supreme Court justices heard the case of a Missouri man pulled over for suspected DUI in 2010 and forced to undergo a blood test.
The American Civil Liberties Union, which represents the defendant, claims that without a warrant the blood test was a violation of the man's Fourth Amendment protection which guards against unreasonable searches and seizures.
Lawyers for Missouri and the Obama administration argue police should be allowed to administer a blood test without a warrant because a person's blood-alcohol level drops as the body processes it, and authorities must get a reading as quickly as possible.
Missouri as well as 49 other states have laws requiring drivers who are arrested on suspicion of driving while drunk to consent to a blood-alcohol test.
Refusal generally leads to suspension of a driver's license.
The court is expected to rule on the case later this year.
(Copyright © 2013 NBC Universal, All Rights Reserved)