In Terry v. Ohio, the United States Supreme Court held that the police practice of 'stopping and frisking' a suspect in public without probable cause does not violate the 4th Amendment's prohibition against unreasonable searches and seizures as long as an officer has a "reasonable suspicion" that the suspect may be committing a crime, has committed a crime, or is planning to commit a crime, and the suspect "may be armed and dangerous.

In Mapp v. Ohio, the United States Supreme Court held that evidence seized without a search warrant cannot be used in state criminal prosecutions under either the 4th Amendment, which protects against unreasonable searches and seizures, or the 14th Amendment, which extends the same protection to state jurisdictions.