The Fourth Amendment to the U.S. Constitution protects people from “unreasonable searches and seizures” that are not supported by probable cause. It generally requires law enforcement officers to obtain a warrant from a judge before they may conduct a search, seize property, or make an arrest. Courts have identified numerous exceptions to this requirement, however. In New Jersey driving while intoxicated (DWI) cases, drivers give their implied consent to provide breath samples to police. A blood draw, however, is considered much more intrusive, and is not covered by the implied consent law. The U.S. Supreme Court has issued several rulings over the years on the question of whether police may order blood drawn from a DWI suspect without a warrant or the suspect’s consent. A ruling from June 2019, Mitchell v. Wisconsin, involved a warrantless blood draw on a suspect who was unconscious. The court vacated the conviction and remanded the case without a clear majority ruling, but five justices were inclined to support warrantless blood draws in certain situations.
If police obtain evidence in violation of someone’s Fourth Amendment rights, that person can ask a court to prevent the use of that evidence against them at trial. This is known as a motion to suppress. The state can offer various justifications for a warrantless search. The “exigent circumstances” exception has featured prominently in DWI cases involving warrantless blood draws. This exception allows police to conduct a search or seize property without a warrant when there is a significant risk of the loss or destruction of material evidence or contraband.
The Supreme Court took up the question of whether the exigent circumstances exception applies to warrantless blood draws in 2013, in Missouri v. McNeely. In a 5-4 ruling, the court found that the breakdown of alcohol in the human body over time is not, by itself, an “exigent circumstance” justifying a warrantless blood draw. It did not, however, foreclose all possibility of an exigent circumstance exception in the future.