Carroll v. U.S.: Supreme Court Case, Arguments, Impact

The Automobile Exception to Warrantless Searches

Cargo of Rumrunner Boat Confiscated by Coast Guard
The contents of a Prohibition-era rumrunner being emptied out after being caught by Coast Guard.

Bettmann /Getty Images

Carroll v. U.S. (1925) was the first decision in which the Supreme Court acknowledged an “automobile exception” to the Fourth Amendment of the U.S. Constitution. Under this exception, an officer only needs probable cause to search a vehicle, rather than a search warrant.

Fast Facts: Carroll v. U.S.

  • Case Argued: December 4, 1923
  • Decision Issued: March 2, 1925
  • Petitioner: George Carroll and John Kiro
  • Respondent: United States
  • Key Questions: Can federal agents search an automobile without a search warrant under the Fourth Amendment?
  • Majority: Justices Taft, Holmes, Van Devanter, Brandeis, Butler, Sanford
  • Concurring: Justice McKenna
  • Dissenting: Justices McReynolds, Sutherland
  • Ruling: Federal agents may search a vehicle without a warrant if they have probable cause to believe they will uncover evidence of a crime.

Facts of the Case

The Eighteenth Amendment was ratified in 1919, ushering the era of Prohibition, when the sale and transport of alcohol was illegal in the U.S. In 1921, federal prohibition agents stopped a car traveling between Grand Rapids and Detroit, Michigan. The agents searched the car and found 68 bottles of liquor stashed inside the car seats. The officers arrested George Carroll and John Kiro, the driver and passenger, for illegally transporting liquor in violation of the National Prohibition Act. Before the trial, an attorney representing Carroll and Kiro motioned to return all evidence seized from the car, arguing that it was removed illegally. The motion was denied. Carroll and Kiro were convicted.

Constitutional Issues

The Fourth Amendment of the U.S. Constitution keeps police officers from conducting a warrantless search and seizure of evidence in someone’s home. Does that protection extend to a search of someone’s car? Did the search of Carroll’s vehicle in accordance with the National Prohibition Act violate the Fourth Amendment?


Counsel on behalf of Carroll and Kiro argued that federal agents violated the defendant’s Fourth Amendment protections against warrantless searches and seizures. Federal agents must obtain an arrest warrant unless someone commits a misdemeanor in their presence. Witnessing a crime is the only way that an officer can avoid getting an arrest warrant. That concept should extend to search warrants. Officers should have to obtain a search warrant to inspect a vehicle, unless they can use their senses like sight, sound and smell, to detect criminal activity.

Counsel for Carroll and Kiro also relied on Weeks v. U.S., in which the court ruled that officers making a lawful arrest may seize unlawful items found in the arrestee's possession and use them as evidence in court. In Carroll and Kiro’s case, officers could not have arrested the men without first searching the vehicle, making the arrest and search invalid.

Counsel on behalf of the state argued that the National Prohibition Act allowed the search and seizure of evidence found in vehicles. Congress intentionally drew a line between searching a house and vehicle in the legislation. 

Majority Opinion

Justice Taft delivered the 6-2 decision, upholding the search and seizure as constitutional. Justice Taft wrote that Congress could create a distinction between cars and houses. For the Supreme Court at the time, the distinction hinged on the function of a car. Vehicles can move, leaving officers little time to obtain a search warrant.

Delivering the opinion for the majority, Justice Taft emphasized that the agents could not search every vehicle traveling on public highways. The federal agents, he wrote, must have probable cause to stop and search a vehicle for illegal contraband. In the case of Carroll and Kiro, prohibition agents had reason to believe the men were involved in smuggling alcohol from previous interactions. The agents had seen the men travel the same route to obtain alcohol in the past and recognized their car. This gave them sufficient probable cause to search.

Justice Taft addressed the interaction between a search warrant and an arrest warrant. He argued that the right to search and seize evidence could not be dependent on the ability to arrest. Instead, whether or not an officer can search a car is dependent on whether or not the officer has probable cause—reason to believe the officer will uncover evidence.

Justice White wrote:

“The measure of legality of such a seizure is, therefore, that the seizing officer shall have reasonable or probable cause for believing that the automobile which he stops and seizes has contraband liquor therein which is being illegally transported.”

Dissenting Opinion

Justice McReynolds dissented, joined by Justice Sutherland. Justice McReynolds suggested that officers did not have sufficient probable cause to search Carroll’s vehicle. Under the Volstead Act, suspicion that a crime has been committed does not always amount to probable cause, he argued. Justice McReynolds wrote that the case could create a dangerous precedent for random roadside searches and arrests.


In Carroll v. U.S., the Supreme Court recognized the legitimacy of the automobile exception to the Fourth Amendment. Building on past cases and existing legislation, the Court emphasized the difference between the search of someone’s home and the search of a vehicle. The automobile exception only applied to federal agents conducting searches until the 1960s when the Supreme Court ruled that it applied to state officers. The exception gradually expanded over the last few decades. In the 1970s, the Supreme Court abandoned Taft’s concern over the mobility of vehicles and adopted language surrounding privacy. Under more recent decisions, officers rely on probable cause to search a vehicle because the expectation of privacy in a car is less than the expectation of privacy in a house.


  • Carroll v. United States, 267 U.S. 132 (1925).
  • “Vehicular Searches.” Justia Law,
mla apa chicago
Your Citation
Spitzer, Elianna. "Carroll v. U.S.: Supreme Court Case, Arguments, Impact." ThoughtCo, Aug. 29, 2020, Spitzer, Elianna. (2020, August 29). Carroll v. U.S.: Supreme Court Case, Arguments, Impact. Retrieved from Spitzer, Elianna. "Carroll v. U.S.: Supreme Court Case, Arguments, Impact." ThoughtCo. (accessed March 28, 2023).