Today, ACLU National Legal Director Steve Shapiro argued an important Fourth Amendment case—Missouri v. McNeely—before the Supreme Court of the United States. While it is generally a good idea not to draw too many conclusions from the apparent attitudes of justices at oral arguments, the argument today appeared to have gone well.

At issue was the question of whether the police need to obtain a search warrant before taking a blood sample from a person stopped for suspicion of drunk driving. The Fourth Amendment prohibits “unreasonable” searches and seizures, and police are generally required to obtain a warrant from a neutral arbiter (a judge or a magistrate) before conducting a search. But, there are exceptions, and the State of Missouri had decided that arrests for drunk driving should be among the exceptions. Missouri defended that position on the grounds that blood-alcohol dissipates rapidly, and police need to obtain an accurate blood alcohol reading quickly in order to be accurate; obtaining a warrant, they claim, would take too much time.

The ACLU argued that obtaining a warrant does not always take a lot of time—many jurisdictions have figured out ways to make the process go quickly—but if the Supreme Court were to say that a warrant for these searches is not required, no police officer would ever bother even trying to obtain one again. That would do away with the important constitutional protection of a neutral arbiter between the police and the public. Blood tests – in particular blood tests conducted at the side of the road by a police officer – are invasive searches, and the police should be required to make an effort at least to get clearance for such a search before hand.

A decision in the case is expected by the end of the current term, in June.  This isn’t the most famous ACLU case at the Supreme Court this term—that would probably be Windsor—but it is certainly important. Protection from unreasonable search and seizure is a difficult right to vindicate. Nobody thinks much about it until they need it. The ACLU of Maine and other affiliates around the country work on similar cases every year, and we can hope that the Supreme Court will issue a positive decision.