During prohibition, officers arranged an undercover purchase of liquor from George Carroll, an illicit dealer under investigation, but the transaction was not completed.

The National Prohibition Act provided that officers could make warrantless searches of vehicles, boats, or airplanes when they had reason to believe illegal liquor was being transported and that law enforced the Eighteenth Amendment.

[6] Underneath their opinion, the majority included a note that Justice Joseph McKenna concurred with them before his retirement earlier in the year.

In brief, they believed that the fact that the case involved bootleggers was prejudicial yet not a justification for creating a broad exception to unreasonable search doctrine.

[9] In United States v. Di Re,[10] the Court declined to extend Carroll to permit searches of passengers in a vehicle that had apparently been lawfully stopped.