Welsh v. Wisconsin

After Welsh (defendant) drove erratically, pulled off the road, and walked home, a police officer traced him through his car's registration and, without a warrant, entered his home that evening with his stepdaughter's consent, finding him in bed and arresting him for driving while intoxicated -- a minor, nonjailable offense under Wisconsin law at the time. Welsh later refused a required breathalyzer test at the station.

Whether the exigent-circumstances exception to the Fourth Amendment permits warrantless entry into a home to arrest an individual for a minor traffic offense.