In the early 1960s, the Court increasingly turned its attention to criminal procedure, which had traditionally been primarily a domain of the states. In "Elkins v. United States" (1960), Warren joined with the majority in striking down the "Silver Platter Doctrine," a loophole to the exclusionary rule that had allowed federal officials to use evidence that had been illegally gathered by state officials. The next year, in "Mapp v. Ohio", the Court held that the Fourth Amendment's prohibition on "unreasonable searches and seizures" applied to state officials. Warren wrote the majority opinion in "Terry v. Ohio" (1968) in which the Court established that police officers may frisk a criminal suspect if they have a reasonable suspicion that the suspect is committing or is about to commit a crime. In "Gideon v. Wainwright" (1962), the Court held that the Sixth Amendment required states to furnish publicly-funded attorneys to all criminal defendants accused of a felony and unable to afford counsel. Prior to "Gideon", criminal defendants had been guaranteed the right to counsel only in federal trials and capital cases.