In fact, the exclusionary rule was found to be necessary to protect the rights guaranteed to Citizens under Fourth Amendment. The exclusionary rule is a legal principle holding that evidence/ witness collected or analyzed which is against U.S. Constitution is inadmissible for a criminal prosecution in a court of law . It aims at preventing misconduct on the part of police.
Before the precedent was set in Weeks v. United States, 232 U.S. 383 (1914), courts used to admit all evidences irrespective of their relevance / legality. Until the decision in Mapp V.Ohio (367 U.S. 643 (1961) ,the rule was applicable at the Federal level only. After this case, the exclusionary rule was also held to be binding on the states through the Fourteenth Amendment, which guarantees due process.
The Exclusionary Rule applies to all citizens or aliens who reside within the United States. It does not applicable to aliens residing outside of U.S. borders. In United States v. Alvarez ,the U.S. Supreme Court decided that property owned by aliens in a foreign country is admissible in court. Prisoners, probationers, parolees, and persons crossing U.S. borders. Corporations, have limited rights under Fourth Amendment.
in 1984. If evidence is collected through independent source and disqualified and later the same evidence was collected through warrant ,that is admissible. The independent source exception allows evidence to be admitted in court if knowledge of the evidence is gained from a separate, or independent, source that is completely legal. This rule was accepted in People v. Arnau.
2. Inevitable discovery doctrine: This matter was discussed in Nix vs. Williams, in 1984. This doctrine states that if evidence is seized in two ways and if one of the evidences is seized physically through illegal means, and there was also a hypothetical evidence of seizure, that hypothetical evidence can be admitted. The doctrine