So why can a car be searched without a warrant? Turns out it is thanks to a decision by Chief Justice Taft, Carroll v. United States. I happened upon this and thought I’d share a decision by Taft after his presidency.
This was a decision that came from a background of Prohibition:
Carroll and Kiro appealed their convictions to the U.S. Supreme Court. They said searching their car without a warrant violated the Fourth Amendment. With a 7-2 decision, the Supreme Court disagreed and affirmed their convictions.
Chief Justice William Howard Taft wrote the opinion for the Court. Taft said the Fourth Amendment protects privacy by requiring searches to be reasonable. It does not, however, require a warrant for all searches. When police believe a private home has evidence of a crime, it is reasonable to require them to get a warrant before searching the place. The house cannot go anywhere.
The case is different with automobiles and other moving vehicles. When a police officer sees an automobile that might contain evidence of a crime, there is no time to get a search warrant. The driver can hide the car or leave the state and escape the police officer's jurisdiction, or area of power. That means it is unreasonable to require the police to get a warrant to search an automobile.
Taft emphasized, however, that officers enforcing the Volstead Act could not stop and search cars at random. To conduct any search, the Fourth Amendment requires probable cause, which means good reason to believe the place to be searched has evidence of a crime. That meant officers enforcing the Volstead Act were limited to searching cars that probably contained illegal alcohol.
The Supreme Court decided that Cronenwett and his fellow officers had probable cause to search Carroll and Kiro's car. Cronenwett knew Carroll was involved in the liquor trade because Cronenwett went undercover to order illegal whiskey from Carroll. Cronenwett also knew that alcohol smugglers often used the road between Detroit and Grand Rapids. Chief Justice Taft said that when Cronenwett saw Carroll driving on that road, Cronenwett had good reason to believe the car contained illegal alcohol, which it did.