The exclusionary rule prevents the government from using most evidence gathered in violation of the United States Constitution. The decision in Mapp v. Ohio established that the exclusionary rule applies to evidence gained from an unreasonable search or seizure in violation of the Fourth Amendment. The decision in Miranda v. Arizona established that the exclusionary rule applies to improperly elicited self-incriminatory statements gathered in violation of the Fifth Amendment, and to evidence gained in situations where the government violated the defendant's Sixth Amendment right to counsel. However, the rule does not apply in civil cases, including deportation hearings. See INS v. Lopez-Mendoza.
If evidence that falls within the scope of the exclusionary rule led law enforcement to other evidence, which they would not otherwise have located, then the exclusionary rule applies to the newly discovered evidence, subject to a few exceptions. The secondarily excluded evidence is called “fruit of the poisonous tree.”
Though the rationale behind the exclusionary rule is based in constitutional rights, it is a court-created remedy and deterrent, not an independent constitutional right. The purpose of the rule is to deter law enforcement officers from conducting searches or seizures in violation of the Fourth Amendment and to provide remedies to defendants whose rights have been infringed. Courts have also carved out several exceptions to the exclusionary rule where the costs of exclusion outweigh its deterrent or remedial benefits. For example, the good-faith exception, below, does not trigger the rule because excluding the evidence would not deter police officers from violating the law in the future.
Under the good-faith exception, evidence is not excluded if it is obtained by officers who reasonably rely on a search warrant that turns out to be invalid. See Arizona v. Evans. Also, in Davis v. U.S., the U.S. Supreme Court ruled that the exclusionary rule does not apply when the police conduct a search in reliance on binding appellate precedent allowing the search. Under Illinois v. Krull, evidence may be admissible if the officers rely on a statute that is later invalidated. In Herring v. U.S., the Court found that the good-faith exception to the exclusionary rule applies when police employees erred in maintaining records in a warrant database.
Evidence initially obtained during an unlawful search or seizure may later be admissible if the evidence is later obtained through a constitutionally valid search or seizure. Murray v. U.S. is the modern interpretation of the independent source doctrine, originally adopted in Nix v. Williams. Additionally, some courts recognize an "expanded" doctrine, in which a partially tainted warrant is upheld if, after excluding the tainted information that led to its issuance, the remaining untainted information establishes probable cause sufficient to justify its issuance. See, for example, the South Dakota Supreme Court decision in State v. Boll.
Related to the independent source doctrine, above, and also adopted in Nix v. Williams, the inevitable discovery doctrine allows admission of evidence that was discovered in an unlawful search or seizure if it would have be discovered in the same condition anyway, by an independent line of investigation that was already being pursued when the unlawful search or seizure occurred.
In cases where the relationship between the evidence challenged and the unconstitutional conduct is too remote and attenuated, the evidence may be admissible. See Utah v. Strieff. Brown v. Illinois, cited in Strieff, articulated three factors for the courts to consider when determining attenuation: temporal proximity, the presence of intervening circumstances, and the purpose and flagrancy of the official misconduct.
The exclusionary rule does not prevent the government from introducing illegally gathered evidence to “ impeach,” or attack the credibility of, defendants’ testimony at trial. The Supreme Court recognized this exception in Harris v. New York as a truth-testing device to prevent perjury. Even when the government suspects perjury, however, it may only use tainted evidence for impeachment, and may not use it to show guilt.
Due to qualified immunity, the exclusionary rule is often a defendant's only remedy when police officers conduct an unreasonable search or violate their Miranda rights. Even if officers violate a defendant's constitutional or statutory rights, qualified immunity protects the officers from a lawsuit unless no reasonable officer would believe that the officers' conduct was legal.
In Vega v. Tekoh (2022) the Supreme Court held that violating Miranda Rights does not provide a basis for a § 1983 claim. Rather, the court asserted that Miranda imposed “a set of prophylactic rules” that only focused on disallowing the use of statements obtained in violation of those rules. Further, the court held that expanding Miranda rights beyond that would impose substantial costs on the judicial system.
[Last updated in November of 2022 by the Wex Definitions Team]
