In a 6–3 opinion by Justice Clark, the Supreme Court extended the exclusionary rule to the states, finding that “all evidence obtained by searches and seizures in violation of the Constitution is, by [the Fourth Amendment], inadmissible in a state court.”
The Mapp case is activist because the Court abused precedent and played legislator to create in state courts the right of a defendant to exclude evidence obtained illegally. Creating such a right allows the Court to circumvent the purposely strenuous process for amending the Constitution.
In Weeks v. United States, the Court held that in federal proceedings involving illegally obtained evidence, such evidence should not aid “[t]he efforts of the courts and their officials to bring the guilty to punishment” because such assistance would render meaningless Fourth Amendment protections against searches and seizures. States, on the other hand, remained free to enforce Fourth Amendment protections by means other than exclusion of illegally obtained evidence. However, Justice Clark’s opinion, overturning a prior decision of the Court in Wolf v. Colorado, 338 U.S. 25 (1949), ended state prerogative and applied the exclusionary rule to the states as an “essential part” of the Fourth and Fourteenth Amendments.
The Fourth and Fourteenth Amendment rights could have been vindicated without setting the criminal free because the constable blundered. Such remedies would include tort or civil rights actions for the constitutional injury, or even criminal prosecutions for officers who maliciously violate the Fourth Amendment. By imposing a remedy without firm constitutional basis, the Mapp decision allowed countless criminals to go free because of police mistakes.