What was the main legal principle behind the decision in Mapp v. Ohio?

The central legal principle established in Mapp v. Ohio is the exclusionary rule, which prohibits the use of evidence obtained in violation of a person's Fourth Amendment rights. This case, decided by the Supreme Court in 1961, determined that states are bound by this rule through the Due Process Clause of the Fourteenth Amendment.

In this case, police conducted a warrantless search of Dolly Mapp’s home and found illegal pornography. The evidence was used against her in a state court, but she argued that it was obtained without a proper search warrant, which violated her constitutional rights. The Supreme Court ruled that evidence obtained through illegal searches and seizures could not be used in state courts, thereby extending the exclusionary rule, which had been previously applied only to federal courts, to states as well. This landmark decision emphasized the importance of protecting individuals' constitutional rights against unreasonable government actions, reinforcing the principle that unlawful evidence should not contribute to a conviction.

Other options related to affirmative action, Miranda rights, and direct evidence use do not pertain to the core holding of the Mapp case, which focused specifically on the protection of citizens from unlawful evidence gathering by law enforcement.