Supreme Court says police must obtain search warrant for blood testing if suspect refuses

by Sami Azhari on April 24, 2013

Blood Test Without Warrant

An important decision was just handed down by the United States Supreme Court concerning driving under the influence. In Missouri v. McNeely, the court was asked to decide whether it was unconstitutional to take blood by force without a search warrant.

The court held that when a DUI suspect refuses a blood test, the police must obtain a search warrant before conducting a nonconsensual blood test.

McNeely was pulled over for speeding and crossing the centerline. The police officer suspected he was intoxicated and asked him to submit to a portable breathalyzer. The driver refused. So, the officer took him into custody and transported him to a hospital for a blood draw. The driver again refused testing. Finally, the police officer ordered a lab technician to take blood anyway. The result was far over the legal limit of 0.08 and McNeely was charged with DUI.

In the trial court, the defendant filed a motion to suppress evidence and the court agreed it was a 4th Amendment violation. Since the defendant refused field sobriety testing, the only evidence of his impairment was the result of the blood test. The prosecution would never meet its burden of proof so they appealed, all the way to the Supreme Court.

The prosecution argued in court that the 4th Amendment does not always require a warrant, and this is true. For example, the emergency exception allows police to conduct a search without a warrant where the defendant could destroy the evidence. The prosecution’s argument in this case was the alcohol in a DUI suspect’s blood dissipates and this creates an emergency exception to the warrant requirement. If the police were required to obtain a search warrant, they said, the suspect’s blood alcohol would decrease and they wouldn’t be able to prosecute.

But the Supreme Court refused to announce a rule allowing nonconsensual blood testing without a warrant.

They said that the dissipation of alcohol in a suspect’s blood is not an emergency situation. Instead, the rate of decrease of alcohol is gradual and predictable. The rate can be determined using science.

(This principle is called retrograde extrapolation, and it is used frequently in DUI prosecutions. When an offender’s blood alcohol concentration is less than 0.08 at the time of testing, the prosecutor would use retrograde extrapolation to prove that it was over 0.08 when he was driving earlier. This evidence requires an expert witness, and is used only in felony DUIs involving injury or death.)

The high court held that police must obtain a search warrant because nonconsensual blood tests violate the accused’s right to be free from unreasonable search and seizure.

We can all breath a sigh of relief after this ruling, because if the prosecution were allowed to do nonconsensual blood tests in every DUI, the results would be problematic. The police would probably take every suspect to the hospital for this purpose, because when it comes to the strength of evidence, a blood test is conclusive proof of guilt.

But hospital workers would not have been pleased with a practice like this. Because of liability concerns, some hospitals would have refused police access to their facility if the only purpose was nonconsensual blood draws. Nurses and lab technicians would have refused to cooperate because they could be sued.

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