In the case of Mitchell v. Wisconsin, the United States Supreme Court has agreed to hear a case from Wisconsin addressing the issue of whether States can have a statute allowing warrantless blood draw of an unconscious suspect. Wisconsin and 29 other States allow warrantless blood draws of an unconscious individual as part of its implied consent laws. In the Mitchell case, the Wisconsin Supreme Court in a divided opinion rejecting the Fourth Amendment challenge with three judges finding that consent was implied and two finding that consent was not required under the circumstances.
Implied consent means that when someone gets their driver’s license, they agree before hand to take a breath or blood test. In other words, the consent is given when the person obtains their driver’s license. If a person does not take a breath or blood test, the State can impose sanctions for refusal. You can read the filings of the Mitchell case on the Scotus Blog.
If the defendant prevails on his Constitutional argument, laws in 29 states will be deemed unconstitutional allowing blood draws for someone that is unconscious. Seven States Courts have found that unconscious blood draw statutes under the name of implied consent are unconstitutional under the Fourth Amendment. The United States Supreme Court will resolve this split in how the Fourth Amendment is interpreted.