What legal principle was established in Mapp v. Ohio?

In the case of Mapp v. Ohio, the Supreme Court established that the Exclusionary Rule, which prevents the admission of illegally obtained evidence in court, applies not only to federal cases but also has been incorporated into state law. This ruling means that evidence gathered in violation of the Fourth Amendment, which protects against unreasonable searches and seizures, cannot be used in state courts just as it is prohibited in federal courts.

This landmark decision was significant because it extended the protections offered by the Fourth Amendment to individuals in all states, ensuring a more uniform standard regarding the admissibility of evidence. As a result of this ruling, law enforcement agencies are required to adhere to constitutional requirements when conducting searches and seizures, promoting accountability and protecting individual rights.

The other choices do not reflect the legal principles established by this case. Warrantless searches may be permissible under specific circumstances, but they are not universally acceptable. The Exclusionary Rule was not limited to federal cases prior to this ruling, and evidence obtained under duress is not admissible, as such practices violate defendants' rights. Thus, the decision in Mapp v. Ohio serves to reinforce constitutional protections at both state and federal levels.