Carroll v. United States

Background

Federal prohibition agents stopped and searched an automobile driven by two men known locally as the Carroll boys and a companion. The agents said they had earlier tried to buy liquor from them and had observed the same car on patrol runs between Detroit and Grand Rapids. On December 15 the agents stopped the car on Pike 16, tore open a seat, found hidden whisky, seized the bottles and the vehicle, and used the liquor as evidence at trial, producing convictions for transporting liquor.

Reasoning

The main question was whether the Fourth Amendment’s protection against unreasonable searches forbids officers from searching a moving vehicle for contraband without a warrant. The Court examined statutes and historical practice that treated movable vehicles differently from private homes because vehicles can be quickly moved out of reach of a warrant. The majority held that when officers have probable cause — a reasonable ground for belief based on facts they possess — they may search an automobile without a warrant and seize contraband; under that rule the search, seizure, and use of the liquor at trial were lawful, and the convictions were affirmed.

Real world impact

Going forward, the decision permits warrantless searches of cars when officers can point to facts creating probable cause that contraband is present. This strengthens enforcement against illegal liquor transport, allows seized vehicle evidence to be used at trial when supported by probable cause, and limits the higher protection that applies inside private homes.

Dissents or concurrances

A separate opinion argued the officers acted on mere suspicion, that the arrest was unlawful, and that evidence obtained after such an arrest should have been excluded.