Blood Evidence of DUI Under Mitchell v. Wisconsin

Blood Evidence of DUI Under Mitchell v. Wisconsin

Posted By Hanson, Gorian, Bradford & Hanich || 25-Sep-2019

In June, the United States Supreme Court decided Mitchell v. Wisconsin, 139 S. Ct. 2525 (2019)—a case involving the issue of whether the police can take blood evidence from an unconscious driver without a warrant in DUI cases. The Court reached a plurality decision, holding that a warrant is not necessary for police to take blood evidence from an unconscious driver if there are exigent circumstances to justify doing so.

Fourth Amendment Protections Against Unreasonable Searches

The Fourth Amendment to the Constitution of the United States prohibits the state from performing an unreasonable search and seizure of a person. In general, a police search must be supported by a warrant indicating that the police has probable cause to search someone for evidence of a crime, signed by a judge or magistrate.

When police conduct a blood alcohol concentration (BAC) test, it is considered to be a search of a person. Thus, BAC tests are only valid if supported by a warrant. In Mitchell, the police drew blood from the defendant without a warrant when he was unconscious. This would qualify as an unconstitutional search unless an exception to the warrant requirement applied.

The Exigent Circumstances Exception

The Supreme Court has consistently held that a warrant is not required for a police search to be considered reasonable, in situations where there is a compelling need for official action and the government does not have enough time to get a warrant. For example, a warrant is not necessary in cases where the destruction of relevant evidence is imminent, and a warrantless search could prevent such destruction. The Court also noted that the need to protect public safety through effective enforcement of DUI laws based on accurate evidence was a compelling need for official action.

Because BAC evidence is subject to natural metabolic processes, there is a limited window of time for police to obtain such evidence. However, the ephemeral nature of BAC evidence does not necessarily mean the court can categorically validate warrantless blood tests as an exigency. The Court emphasized that an additional factor must be present to make conducting BAC test sufficiently urgent. For example, if police are too bogged down with more important duties related to the DUI, it would be unreasonable to require them to secure a warrant in light of such responsibilities.

In Mitchell, the Court found that drawing the defendant’s blood to secure BAC evidence was reasonable because his unconsciousness prevented the police from conducting a chemical breath test.

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Categories: Criminal Defense, DUI