Carroll v. United States

The decision in Carroll v. United States was the first time that the Supreme Court recognized the car search exception to the warrant requirement. The Court continued to articulate the position it took with the Carroll case, that privacy interests in a car have constitutional protection, but a car's mobility justifies less broad protection and is thus exempt from traditional warrant requirements. In 1931, the Court upheld the search of a parked car because police could not know when the car might be moved. A 1948 decision appeared to limit the automobile exception to vehicles suspected of violating federal laws. But in 1949, the Court upheld warrantless searches of cars as long as the police had probable cause to believe the vehicle was involved in illegal activity.

In the 1960s, the Supreme Court applied the same limits to state police as to federal authorities regarding warrantless automobile searches. The Court upheld the warrantless search of a car as long as a week after the owner's arrest, since the car was subject to government forfeiture. The Court has permitted law enforcement officers to search cars after they have been towed to a police garage from an arrest site. Evidence obtained in a routine warrantless search of an impounded vehicle was deemed admissible in court. They have also ruled that a warrant is not necessary when taking paint samples from a car parked in a public lot.

In the 1977 United States v. Chadwick trial, the Court brought up the concept of a person's expectations of privacy being less in an automobile than in other things, such as a locked piece of luggage. Since the Chadwick ruling, the Supreme Court has continued to enlarge the automobile exception begun with Carroll. In 1978, the Court decided that passengers could not object to a warrantless search of a car. This ruling linked the Fourth Amendment rights of passengers more closely to property concepts than to privacy interests. In the 1980s, the Court ruled that law enforcement officers, with probable cause to search a car, could also search closed containers in that car. In the 1990s, the Court found that the police could search an entire car when they had probable cause only to search a container in the car. Over the decades the Court has moved away from Taft's reasoning about the mobility of cars making warrantless searches a necessity to a concept of the limited expectations of privacy that people have regarding their automobiles.