Terry v. Ohio, 392 U.S. 1 (1968), was a landmark U.S. Supreme Court decision in which the Court ruled that it is constitutional for American police to "stop and frisk" a person they reasonably suspect to be armed and involved in a crime. Specifically, the decision held that a police officer does not violate the Fourth Amendment to the U.S. Constitution's prohibition on unreasonable searches and seizures when questioning someone even though the officer lacks probable cause to arrest the person, so long as the police officer has a reasonable suspicion that the person has committed, is committing, or is about to commit a crime. The Court also ruled that the police officer may perform a quick surface search of the person's outer clothing for weapons if they have reasonable suspicion that the person stopped is "armed and presently dangerous." This reasonable suspicion must be based on "specific and articulable facts," and not merely upon an officer's hunch. This permitted police action has subsequently been referred to in short as a "stop and frisk", "stop, question, and frisk," or simply a "Terry stop." The Terry standard was later extended to temporary detentions of persons in vehicles, known as traffic stops; see Terry stop for a summary of subsequent jurisprudence. The rationale behind the Supreme Court decision revolves around the notion that, as the opinion argues, "the exclusionary rule has its limitations." According to the Court, the meaning of the rule is to protect persons from unreasonable searches and seizures aimed at gathering evidence, not searches and seizures for other purposes (like prevention of crime or personal protection of police officers). Background Legal history "Stop-and-frisk" is a police practice where a police officer stops a person suspected of involvement in a crime, briefly searches their clothing for weapons, and then questions them, all without requiring the person's consent and without enough grounds to arrest them. Historically, all major American police forces routinely employed the stop-and-frisk practice. It was historically viewed as a "low visibility" police procedure and was "largely ignored by commentators and dealt with ambiguously by most courts." In the early 1960s, several major changes in American criminal law raised the issue's importance. First, in its 1961 decision Mapp v. Ohio, the U.S. Supreme Court ruled that the exclusionary rule—which prevents the government from using evidence in criminal prosecutions if it were illegally obtained—applies to the U.S. states as well