On April 17, 2013, the United States Supreme Court released their decision in Missouri v. McNeely and specifically held that "in drunk driving investigations, the natural dissipation of alcohol in the bloodstream does not constitute an exigency in very case sufficient to justify conducting a blood test without a warrant." Mr. McNeely was stopped for speeding and eventually investigated and arrested for operating while intoxicated. The officer had observed bloodshot watery eyes, the smell of alcohol, and he performed poorly on his field sobriety tests. The officer arrested him and offered him a breath test which Mr. McNeely refused, so the arresting officer took him to a nearby hospital and had his blood withdrawn without obtaining a warrant. Mr. McNeely sought suppression of the blood test evidence arguing that it was obtained in violation of his Fourth Amendment Rights. The District Court agreed and so did the Missouri Supreme Court. The U.S. Supreme Court granted certiorari to "resolve a split of authority on the question of whether the natural dissipation of alcohol in the bloodstream establishes a per se exigency that suffices on its own to justify an exception to the warrant requirement for nonconsensual blood testing in drunk driving investigations."
The majority opinion authored by Justice Sotomayor, reasoned that the warrant protections of the Fourth Amendment may not be ignored simply because alcohol naturally dissipates out of the body. The Court required a totality of the circumstances approach be taken in each individual case to determine whether the facts and circumstances of may provide an emergency situation whereby relieving the government of the need for a warrant. The majority opinion however did not discuss what factors may be relevant to this analysis but did caution that the natural dissipation of alcohol and the time needed to obtain a warrant would be important factors.
The majority opinion also rejected a bright line approach suggested by the Chief Justice in which officers would be allowed to do a warrantless blood draw if the officer felt that he could not obtain a warrant in the time taken to get the person to the hospital. The majority rationalized that this "modified per se rule" provided by the Chief Justice would "distort law enforcement incentives" by discouraging efforts to expedite the warrant process. The majority also cautioned that this approach would make roadside blood draws done by police officers a more attractive approach.
Additionally, the majority was quick to point out that advancements in technology have streamlined the warrant process and make them much easier and quicker to obtain. The majority also suggested that States have other significant tools to obtain chemical test results other than warrantless blood draws and that those avenues should not be forgotten.
Only time will tell how this ruling will be applied on a case by case basis but for the meantime, suffice it to say that the natural dissipation of alcohol from the human body will not allow a warrantless blood draw from a drunk driving suspect under the Fourth Amendment. The case of State v. Harris, 763 N.W.2d 269 (Iowa 2009), provides a similar discussion of warrantless blood draws in the State of Iowa.