Which case established the exclusionary rule?

The establishment of the exclusionary rule is primarily attributed to the Supreme Court case Mapp v. Ohio. This landmark decision was made in 1961 and extended the exclusionary rule, which prohibits the use of illegally obtained evidence in criminal trials, to state courts.

Prior to Mapp v. Ohio, the exclusionary rule was primarily applicable to federal courts, stemming from the case Weeks v. United States in 1914. However, Mapp v. Ohio incorporated this rule to the states through the Fourteenth Amendment's Due Process Clause. In this case, police officers conducted an unlawful search of Dollree Mapp's home without a proper warrant and found materials that led to her conviction for possessing obscene materials. The Supreme Court ruled that the evidence obtained from the illegal search was inadmissible, thus reinforcing the exclusionary rule in state courts and ensuring that constitutional protections against unreasonable searches and seizures were upheld universally.

The other cases listed, while significant in their own right, do not pertain to the establishment of the exclusionary rule. Terry v. Ohio relates to stop-and-frisk procedures, Miranda v. Arizona is known for the Miranda rights regarding self-incrimination, and Gideon v. Wainwright addresses the right to legal counsel