Can police draw blood from an unconscious person without a warrant?

Colorado’s express consent law provides that drivers, by virtue of driving on state roadways, have already consented to take a breath or blood test when an officer has probable cause to believe the person is impaired by alcohol or drugs. Refusal to take the test results in a revocation of the driver’s license. Moreover, blood tests can be performed on people who are unconscious.

The issue of unconscious people being given blood tests to determine their level of intoxication has just come before the U.S. Supreme Court. The case involves a man who was pulled over in Wisconsin in 2013. Wisconsin has an implied consent law that is similar to Colorado’s express consent law.

A preliminary breath test pegged the man’s blood alcohol content at 0.24, or three times the legal limit. He was arrested.

On the way to the hospital for a blood test, the man became unconscious and could not be roused. Nevertheless, the arresting officer ordered a blood test be performed. This was done despite the Wisconsin law that gives people the right to refuse such a test and lose their license.

The defendant argued that his Fourth Amendment right to be free from unreasonable searches and seizures by the government had been violated. In a case called Missouri v. McNeely, the U.S. Supreme Court reasoned that a blood test is intrusive enough that the Fourth Amendment comes into play. It ruled that a warrant is required whenever police draw blood from DUI suspects unless there is a legitimate emergency preventing them from obtaining one. Furthermore, the natural metabolism of alcohol in the blood over time does not constitute such an emergency.

However, the Wisconsin Supreme Court ruled that the state’s implied consent statute eliminated the need for a warrant as long as the officer has probable cause to believe the suspect has been driving under the influence. In this case, the officer had the preliminary breath test and his own observation of the suspect acting in an intoxicated fashion, and these provided probable cause.

Can a state law overcome a constitutional requirement? The Supreme Court’s decision will affect at least 29 states, including Colorado, with implied or express consent statutes like Wisconsin’s.