Birchfield v. North Dakota - warrantless breath tests for DWI suspects are legal, but warrantless blood tests are not (well, kinda...)
Today the U.S. Supreme Court handed down a widely anticipated case on DWI law. At issue is whether or not the Fourth Amendment allows for warrantless breath and blood tests of people suspected of driving while intoxicated. The Court held that no warrant is required to take a breath test from a DWI suspect, but that a blood test does require a warrant.
The reason I put "kinda" in the description above is the Court did not actually ban warrantless blood tests, they said it couldn't be considered a crime to refuse a warrantless blood test. The Court said administrative penalties (like license suspensions) were still allowed for refusing a warrantless blood test, but States cannot punish someone criminally for doing so. In Arkansas, refusal to submit to a blood test was only a violation anyway (see my "Cases and Courts" page for more information). Since a violation is only punishable by up to a $100 fine, this case doesn't really help DWI suspects in Arkansas. But in states that levied severe punishment for refusal this case is a real game-changer.
This does not change the fact that police can still request a warrantless blood test, they just can't imply that refusing one is a crime (though remember you will still suffer administrative consequences). If a person agrees to submit to a test then it can be used against them.