What does the exclusionary rule, established in Mapp v. Ohio, state?

The exclusionary rule, established in the landmark case Mapp v. Ohio, asserts that evidence obtained in violation of a defendant's constitutional rights, particularly those protected by the Fourth Amendment against unreasonable searches and seizures, cannot be admitted in court. This rule is crucial for upholding the integrity of the judicial system and ensuring that law enforcement officials adhere to legal protocols when gathering evidence. The ruling extended the exclusionary rule to state courts, reinforcing the idea that protecting citizens' rights is essential, regardless of the level of government involved in the investigation. This means that if law enforcement conducts a search without a warrant or probable cause and discovers incriminating evidence, that evidence cannot be used against the defendant in a trial.

The other options do not accurately reflect the principles established in Mapp v. Ohio. For instance, the requirement that evidence must be disclosed to the defense pertains to the discovery process and is separate from the exclusionary rule. Similarly, while warrants are necessary for obtaining certain types of evidence, the rule does not stipulate that all evidence must come from warrants, nor does it state that all evidence is admissible in court, which contradicts the very nature of the exclusionary rule.