What principle was established in Mapp v. Ohio regarding illegal searches?

The principle established in Mapp v. Ohio is that the exclusionary rule applies to state courts. This landmark case addressed the issue of illegal searches and seizures, stemming from the Fourth Amendment, which guards against unreasonable searches. Before this case, the exclusionary rule, which prevents evidence obtained through illegal means from being used in court, was primarily enforced only at the federal level.

With Mapp v. Ohio, the U.S. Supreme Court ruled that evidence obtained in violation of the Fourth Amendment is inadmissible in state courts as well. This ruling significantly reinforced the protection of individual rights against unlawful searches and set a precedent that any evidence gathered in violation of constitutional rights cannot be used to prosecute individuals, thus promoting accountability in law enforcement practices.

In contrast, the other options reflect misconceptions about search and seizure laws. They do not accurately capture the legal principle established in this case, which centers specifically on the application of the exclusionary rule rather than on confessions, blanket legality of police methods, or the legality of warrantless searches in all contexts.