What key decision was made in Mapp v. Ohio regarding searches?

In Mapp v. Ohio, the key decision established that the Fourth Amendment, which protects against unreasonable searches and seizures, applies to state governments through the Due Process Clause of the Fourteenth Amendment. This landmark ruling extended the exclusionary rule—previously applicable only to federal cases—to state courts, meaning that evidence obtained in violation of the Fourth Amendment cannot be used in state prosecutions.

This decision was significant because it reinforced the principle of constitutional protection against unlawful searches, ensuring that all individuals, regardless of the level of government involved, have the right to privacy in their homes and possessions. The ruling also emphasized the notion that states cannot disregard federally protected rights, thereby strengthening civil liberties at the state level. This was a pivotal moment in the incorporation of the Bill of Rights into state law, ensuring uniform protection across the country.