The “exclusionary rule” prohibits the use of most evidence if it was improperly obtained. For almost a hundred years after the passage of the 4th Amendment, few people objected to the use of such tainted evidence at trial. The issue was tested in 1822, in United States v. La Jeune, when the defense argued that certain evidence should be inadmissible in court because it was obtained improperly. Justice Story responded that such “evidence is admissible on charges for the highest crimes, even though it may have been obtained by a trespass upon the person, or by any other forcible and illegal means.” Story acknowledged that evidence is sometimes acquired contrary to law, yet he was “not aware, that such evidence has upon that account ever been dismissed for incompetency.” A defendant who was the victim of an unreasonable search and seizure might still be able to sue for damages against the offending officer, but only for the improper search or seizure, not for any damages incurred by subsequent criminal prosecution.
It was not until 1914, in Weeks v. United States, that the United States Supreme Court ruled that improperly obtained evidence should be excluded from a criminal trial pursuant to the 4th Amendment. This “exclusionary rule” was controversial from the moment it was announced, and the controversy continues to this day. Those who defend the exclusionary rule essentially argue that, without it, the police have strong incentives to engage in unreasonable searches and no countervailing incentive to obey the 4th Amendment.
Supporters of the rule also argue that using ill-gotten evidence compounds the original injury. If seizing private property without a warrant is an invasion of privacy, then scrutinizing it in court constitutes a second invasion.
Moreover, supporters argue, when a wrong has been committed, the principle of remediation demands that the victim be placed, whenever possible, in the same condition he was in prior to being wronged. In the case of evidence discovered by an improper search and seizure, the exclusionary rule places a victim in the same condition he or she would have been in if the Constitution had never been violated.
Ultimately, the exclusionary rule is meant to prevent future abuses by the police. Indeed, Justice Stewart, in Elkins v. United States (1960), claimed that deterrence was its only purpose. Denying that the rule would offer any kind of reparations, he asserted instead: “Its purpose is to deter—to compel respect for the constitutional guaranty in the only effectively available way—by removing the incentive to disregard it.”
Those who oppose the exclusionary rule have argued that the guilt of the offending officer does not absolve the suspect of his own crime, and excluding important evidence will allow criminals to escape judgment. Furthermore, suppressing evidence does not place a suspect in the same condition he would be in if it were never discovered; it places him in a better position. If the evidence had not been obtained through an improper search, there would still be a chance that it could be discovered through proper channels. In many cases, therefore, excluding evidence effectively hands a suspect a get-out-of-jail-free card.
Opponents of the exclusionary rule would prefer to enforce the 4th Amendment in the same way that it was enforced during its first hundred years: by making the offending officer liable for damages. Opponents counter that very few convicted criminals could convince juries to award them damages for the illegal searches that led to their convictions. Moreover, even innocent people would be unlikely to file such a lawsuit, especially considering that police officers are immune from civil liability so long as they can show that they were acting in good faith.
Nonetheless, it is hard to see someone like a convicted child rapist go free just because a police officer made a mistake. Justice Burger claimed in 1971 that if Congress were to review the 50-year history since the exclusionary rule was enforced, it would find “thousands of cases in which the criminal was set free because the constable blundered and virtually no evidence that innocent victims of police error . . . have been afforded meaningful redress” (Bivens v. Six Unknown Fed. Narcotics Agents).
Finally, those who defend the exclusionary rule claim that it often forces some clarification of the meaning of an unreasonable search. If the courts did not rule on this question when considering whether evidence was admissible, the question would be unlikely to come up except in the exceptional case when a suspect sues a police department for damages. On the other hand, its detractors would argue that the numerous and varied circumstances under which evidence is now scrutinized for its admissibility only add to the complexities, confusions, and inconsistencies in our interpretation of the 4th Amendment.
In 1961 the 4th Amendment was incorporated against the states by the Due Process Clause of the 14th Amendment. The Supreme Court decided in Mapp v. Ohio that any evidence gained through an improper search was inadmissible whether the trial was held in a state or a federal court. Even before its incorporation, however, many states had already added exclusionary rules to their interpretations of their own state constitutions.