State v. Villarreal

The Texas Court of Criminal Appeals held that mandatory blood draws in DWI cases under the Texas Transportation Code's implied consent provisions violate the Fourth Amendment when conducted without a warrant. The court ruled that the implied consent statute does not create an exception to the warrant requirement and that the natural dissipation of alcohol in the bloodstream does not automatically create exigent circumstances justifying a warrantless blood draw.

This landmark decision effectively ended the practice of routine warrantless blood draws in Texas DWI cases and required law enforcement to obtain warrants for blood evidence.