Mapp v. Ohio established which rule about evidence?

• A. Exclusionary rule
• B. Double jeopardy rule
• C. Miranda rights
• D. Good faith exception

Answer: (A)

Evidence obtained in violation of the Fourth Amendment cannot be used in court. Mapp v. Ohio extended this rule to state courts by applying the exclusionary rule to the states through incorporation, so illegally seized evidence is not admissible in state prosecutions. This safeguard ensures that constitutional rights are upheld across all levels of government and that violations by law enforcement don’t generate convictions through tainted evidence. The other options refer to distinct protections: double jeopardy protects against being tried twice for the same offense; Miranda rights concern informing detainees of their rights during interrogation; the good faith exception—allowing evidence obtained under a faulty warrant to be used—was established in a different case and does not describe Mapp’s ruling.