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The U.S. Supreme Court ruled today in the case of Missouri vs. McNeely that police officers must “usually” obtain a warrant before conducting blood draws on suspected impaired drivers. Justice Sotomayor delivered the Court’s opinion that the natural metabolism of alcohol does not grant a “per se” exigency that allows a blanket exception to the 4th Amendment requirement of obtaining a warrant in DUI cases, but that exigency must be determined on a case by case basis. The 8-1 opinion rejected the position held by the Obama administration and more than 30 states that all argued the natural dissipation of alcohol in the bloodstream automatically created an exception to the requirement for a warrant.

In 2010, Tyler McNeely was pulled over in Missouri by a police officer who noticed signs of impairment. McNeely refused a breath test twice, so the officer had him transported to a hospital where a blood draw was performed without a warrant or McNeely’s consent. McNeely’s BAC came back at 0.154, and he was charged with DWI. He moved to have the results suppressed arguing that the warrantless blood draw was a violation of his 4th Amendment rights.

In today’s ruling the Court rejected the argument and stated exigency needs to be examined on a case-by-case basis with the totality of circumstances being considered. The Court stated that advances in technology in obtaining a warrant, and the BAC dissipation that is happening, whether a warrant exists or not, in the time it takes to transport a person to a testing facility also helps nullify the state’s argument.

The Court acknowledged that drunk driving in the US is a serious problem, but that states have a “broad range of legal tools” to obtain BAC evidence, and that efforts to combat drunk driving in states that do not allow warrantless blood draws have not been compromised. However, the justices seemed to disagree over what factors should determine when police can draw blood from an unwilling suspect without a magistrate’s approval.

Justice Clarence Thomas wrote in the dissenting opinion that Congress has made federal highway grants conditional on the passing of laws making it illegal to drive while impaired (0.08 BAC), with some states, including Missouri, having additional penalties for driving with a BAC of 0.15 or higher. An accurate knowledge of BAC is needed for enforcement of these laws according to Justice Thomas, and that, “Nothing in the Fourth Amendment requires officers to allow evidence essential to enforcement of drunk-driving laws to be destroyed while they wait for a warrant to issue.”

The Court did not give clear guidelines about when a warrant is not needed. Click here to read the text of the Missouri vs McNeely decision.

What is your interpretation of the Court’s ruling? Stay tuned for a follow up post on what this means in the real world of law enforcement and the prosecution of drunk driving cases nationwide.

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Kathleen Brown

Kathleen Brown

Kathleen Brown has 20+ years of experience as a public relations and marketing communications professional, including 16 years working with media, lawmakers, special interests, and government agencies on the issues of drunk driving and other alcohol-related crime. Brown first joined AMS in 2001 as an independent consultant, working with the board of directors to build private equity for final R&D and product launch of the first generation of SCRAM. She joined the staff full-time in 2004. She has worked extensively with the news media as a topic expert for industry data and research studies, community corrections, monitoring technologies, drunk driving, alcohol misuse, and the judicial system. She is currently director of Marketing & Public Relations for AMS.