The exclusionary rule is fundamental legal doctrine in the united states that prevents evidence obtained in violation of defendant’s constitutional rights from being used in criminal court. This rule is primarily designed to protect individuals from unlawful government  action and deter law enforcement from engaging in unconstitutional practices. It is grounded in several constitutional provisions, including the fourth amendment, which protects against unreasonable searches and seizures ( mapp v. ohio, 1961), the fifth amendment, which prohibits self-incrimination and excludes illegally coerced confessions (miranda v. arizona,1966), and the sixth amendment, which guarantees the right to counsel. Evidence obtained in violation of these rights is generally inadmissible in court.

The exclusionary rule applies to criminal cases at both state and federal levels but does not extend to civil cases, deportation hearings, or parole revocation proceedings. It also encompasses the fruit of the poisonous tree doctrine, which excludes derivative evidence obtained through illegal means unless an exception applies. Exceptions to the rule include the good faith exception, allowing evidence if law enforcement acted with reasonable belief in their action ‘ legality, the independent source doctrine, permitting evidence obtained independently of the illegal conduct, and the inevitable discovery doctrine, which allows the use of evidence that would have been found through lawful means. 

Additionally, the impeachment exception permits the use of illegally obtained evidence to challenge a defendant’s credibility. To invoke the exclusionary rule, a defendant must file a motion to suppress evidence, and the court will determine whether the evidence was unlawfully obtained and whether any exception apply. Ultimately, the exclusionary rule upholds fairness in criminals proceedings and serves as a critical safeguard against law enforcement misconduct.