The supreme court made the exclusionary rule applicable to the states, holding that all evidence obtained by searches and seizures in violation of the constitution are by the same authority inadmissible in state court in:

The asnwer is: Mapp v. Ohio

In legal term, exclusionary rule refers to the law that banned the use of illegaly obtaned criminal evidence during a criminal trial.

After the Mapp v. Ohio, the exclusionary rule was made with the clause to protect against unreasonable search and seizures.