In which case was the "good faith" exception to the exclusionary rule established?

The "good faith" exception to the exclusionary rule was established in United States v. Leon. This case addressed the issue of whether evidence obtained through a search warrant, which was later found to be unsupported by probable cause, should be excluded from trial. The Supreme Court ruled that evidence obtained in good faith reliance on a warrant issued by a neutral and detached magistrate can be admissible even if that warrant is ultimately found to be invalid. This decision aimed to balance the need for effective law enforcement with the protection of individual rights, acknowledging that penalizing officers who acted in good faith serves little purpose in deterring police misconduct.

This concept allows for the admission of evidence when officers reasonably believe they are following legal procedures, thereby promoting judicial efficiency while still upholding the core principles of the Fourth Amendment.