Which decision extended the exclusionary rule of search and seizure to state court proceedings?

The decision that extended the exclusionary rule of search and seizure to state court proceedings is Mapp v. Ohio. This landmark case, decided in 1961, involved the application of the Fourth Amendment, which protects individuals from unreasonable searches and seizures. Prior to Mapp v. Ohio, the exclusionary rule—which mandates that evidence obtained illegally cannot be used in court—was only applicable in federal courts.

In this case, the Supreme Court ruled that the exclusionary rule must also apply to state courts through the Fourteenth Amendment's Due Process Clause. This ruling was significant because it ensured a uniform protection of constitutional rights across both federal and state judicial systems, reinforcing the commitment to upholding due process.

Katz v. United States addressed the issue of privacy in public spaces, while Wallace v. Jaffree dealt with state-sponsored prayer in schools. Cohen v. California focused on free speech issues but did not relate to search and seizure or the exclusionary rule. Thus, these cases do not connect directly to the constitutional implications established in Mapp v. Ohio regarding the exclusionary rule's application in state courts.