Which case established that the exclusionary rule applies to the states?

• A. Mapp v. Ohio
• B. Weeks v. U.S.
• C. New York v. Belton
• D. California v. Greenwood

Answer: (A)

The idea being tested is how the exclusionary rule was extended from federal cases to include state prosecutions. Weeks v. U.S. established the rule for federal law enforcement, making illegally obtained evidence unusable in federal courts. But it did not bind the states. The pivotal shift came with Mapp v. Ohio, where the Supreme Court held that the Fourth Amendment’s protections against unreasonable searches and seizures apply to the states through the Fourteenth Amendment’s due process clause. This makes illegally obtained evidence inadmissible in state courts as well, effectively incorporating the exclusionary rule at the state level. The other cases involve different Fourth Amendment issues, not the expansion of the rule to the states.