The exclusionary rule forbids the introduction of certain evidence in court, in an attempt to ensure that the state and federal governments do not violate individuals’ constitutional rights. The rule applies to criminal trials and as a general matter forbids the use of evidence that was obtained as a result of a violation of the Fourth or Fifth Amendments in the government’s case-in-chief, that is, in the part of the trial where the government presents its evidence of the defendant’s guilt. Accordingly, if the police, on a wild hunch, break down a person’s front door and discover drugs in the house, the drugs may not be used to convict the homeowner of drug possession.
There are several exceptions to this rule, however, which will be discussed in more detail below. The rule does not apply to civil proceedings and does not apply to pretrial or sentencing hearings in a criminal prosecution. Even at trial, if the defendant testifies falsely, the government can rebut the defendant’s testimony by using the illegally obtained evidence. Furthermore, if the police obtain a warrant that is defective in some way, so that the resulting search is unconstitutional, the evidence found may still be admitted at trial in the prosecution’s case-in-chief if the police were acting in reasonable good faith on the warrant.
The exclusionary rule ordinarily applies to ban the government from using not only the evidence that is found during an unconstitutional search, but also that evidence that is found because of that search. So, a search that turns up a lead to further evidence will result in suppressing both the lead and the additional evidence. But not all evidence that is found as a result of the unconstitutional action will be excluded. If the connection between the illegality and the evidence is too attenuated, or if the police would have found the evidence by legal means, then the exclusionary rule does not apply. Lastly, the exclusionary rule is an available remedy only for the individual whose person or property was searched or seized. If a search of a person turns up evidence of his friend’s crime, the friend will usually be unable to have that evidence suppressed.
The Supreme Court has held since Weeks v. United States (1914) that the exclusionary rule bars the use in federal trials of evidence that was obtained by violating the Fourth Amendment, which prohibits ‘‘unreasonable searches and seizures.’’ It was not until Mapp v. Ohio (1961), however, that the Supreme Court required states to use the exclusionary rule as well. The rule was originally based on two considerations. First, the Court wanted to deter police from violating the Constitution. If any evidence illegally seized by the police could not be used in the defendant’s trial, then (the theory went) there would be no reason to commit the violation in the first place. Second, the Court thought it was wrong to involve the judicial process in the constitutional violation. That is, even though the judiciary did not commit the unreasonable search, the Court thought it improper that the Court take part in the constitutional violation by using its fruits. In later years this second justification has fallen out of favor and the courts now exclusively rely on the deterrence rationale, as the Supreme Court itself pointed out in Stone v. Powell (1976) and United States v. Janis (1976).
The rule remains controversial today because its effect is to make it more difficult to convict guilty criminal defendants. In the example in the first paragraph, there is no doubt that the homeowner whose house was unconstitutionally searched by police was guilty of drug possession. Justice Benjamin Cardozo, who was then a judge on the New York Court of Appeals, most famously stated the disadvantage of the exclusionary rule: ‘‘The criminal is to go free because the constable has blundered’’ (People v. Defore ). Moreover, the exclusionary rule does nothing to compensate innocent persons for violations of their Fourth Amendment rights. An illegal search that turns up no evidence will never be subject to the exclusionary rule because there will be no trial, yet the rights of that innocent person were violated just as much as were the rights of the manifestly guilty person for whom the exclusionary rule is a get-out-of-jail-free card. Nevertheless, to the extent the exclusionary rule deters unlawful police conduct, there will be fewer violations of the Fourth Amendment rights of the innocent and the guilty, so perhaps the rights of the law-abiding are served in some way by the application of the rule to the nonlaw-abiding.
There are considerable instances when the rule does not deter police conduct. This can happen for several reasons. First, the officers may not know that their conduct violates the Constitution. They may think they are following the Fourth Amendment, but a judge may later disagree. In that instance, the exclusionary rule—like any penalty—will not deter a violation, for the officer will not know that he is subjecting himself to the penalty. Second, if the person whose property is searched is not prosecuted (or if the case is plea bargained), then the exclusionary rule never comes into play. The exclusionary rule then does nothing to protect the rights of persons who will not be prosecuted. As a result, whatever deterrent effect the exclusionary rule has is lessened because a certain portion of unconstitutional searches will not result in exclusion. Third, officers may not be deterred from committing violations if the exclusionary rule is applied months or years after the unconstitutional search, and the passage of time makes it hard for the officer to learn from his error, if he is ever told of the exclusion at all. Fourth, an officer bent on violating the Fourth Amendment may be able to lie in court and avoid the exclusionary rule that way, lessening the deterrent value of the rule.
On the other hand, police departments have become more conscious of the Fourth Amendment in the years since Mapp, and officers whose searches cannot yield convictions eventually feel some heat from the officials whom the voters expect to put criminals behind bars. Even as to the first objection— that officers cannot reasonably be expected to know the details of Fourth Amendment doctrine— there is vast disagreement. Several states have concluded that the exclusionary rule does deter officers, and if it causes officers to be cautious even when they are approaching the constitutional line, so much the better.
The Supreme Court has decided, however, that the police act ‘‘reasonably,’’ and therefore there is no need to exclude evidence if the police were acting reasonably in good faith reliance on a warrant— even if that warrant is later determined to be invalid (United States v. Leon ). If, for example, the police lack probable cause to obtain a search warrant, but they apply for the warrant anyway and a judge issues one, evidence found in that search will be admissible if the officers’ reliance on the warrant was reasonable and in good faith. The Court has decided that police cannot be expected to second-guess judges, and if a judge finds that there is probable cause, the police should not be expected to doubt that determination.
There are, however, some important limitations on the use of the good faith exception. If the judge signs the warrant because he is deceived by the police, then the police are not acting in good faith and the exception does not apply. Also, if probable cause is so lacking, or if the warrant wholly fails to specify the place to be searched or the items to be seized such that no reasonable officer would believe that the warrant is valid, the exception will not apply.
Leon’s good faith exception is merely one instance where illegally obtained evidence is admitted in court despite the exclusionary rule. Perhaps most significant, the exclusionary rule does not apply in civil cases, and even in criminal cases the rule applies only to trials. Accordingly, illegally obtained evidence may be introduced before grand juries or at sentencing hearings. The Supreme Court has explained that the exclusionary rule is most likely to achieve its deterrent objective in criminal trials (as the government is often tempted to violate the Fourth Amendment in the investigation of crimes), and that accordingly the rule need not be extended to cover other proceedings. Nevertheless, as critics have pointed out, if the integrity of the courts is thought to be undermined by the use of illegally obtained evidence (as Weeks maintained), the admission of such evidence in civil and criminal trials would equally undercut that interest.
Habeas corpus proceedings—which are technically civil but often involve federal court review of state court criminal prosecutions—are somewhat more complicated. A defendant convicted in state court can bring an action for a writ of habeas corpus in federal court, which would require the state to justify its continued imprisonment of the criminal defendant. Ordinarily, if the federal court finds that the state conviction was obtained through a violation of the Constitution—for example, because the state failed to respect the defendant’s request for a jury trial—the federal court would require the state to conduct a new trial or release the prisoner. Under Stone v. Powell, however, the result is different when the prisoner objects to his conviction based on a violation of the Fourth Amendment exclusionary rule.
Suppose that a state tries a defendant for murder, and a key piece of evidence is the defendant’s knife stained with the victim’s blood. The police obtained that knife, however, by violating the Fourth Amendment— perhaps because they unreasonably failed to obtain a search warrant. Mapp makes the exclusionary rule applicable to the initial state trial. The state courts, however, believe that no warrant was necessary, so they allow the knife into evidence. After the defendant is convicted, he petitions for a writ of habeas corpus, claiming that his constitutional rights were violated. Even if the federal court hearing his claim agrees that the police violated the Constitution, the defendant will not receive a new trial. Stone v. Powell concluded that the deterrent effect on the police of applying the exclusionary rule to habeas corpus proceedings simply does not justify the costs of setting convicted, guilty criminals free.
Even this rule, however, has limits. If the state gave the defendant no chance at the original trial to argue that his Fourth Amendment rights were violated, then he would be able to argue the violation on habeas review. And—although the Supreme Court has not yet decided this question—if the state court decision admitting the evidence was clearly and obviously wrong, the federal court might conclude that in effect the defendant was not given ‘‘an opportunity for a full and fair litigation of [his] Fourth Amendment claim,’’ requiring a new trial. As a general matter, however, a prisoner will not receive habeas relief if a state court wrongly admits unconstitutionally obtained evidence at his trial.
Furthermore, the exclusionary rule applies only to the prosecution’s case-in-chief—that part of a criminal trial where the government sets forth its proof of the defendant’s guilt. If the defendant takes the witness stand to testify, however, the prosecution can use unconstitutionally obtained evidence to ‘‘impeach’’ the defendant, that is, to demonstrate that the defendant’s statements are untrue. The Court has reasoned that defendants should not be able to use the exclusionary rule to enable them to commit perjury (United States v. Havens ). This impeachment exception, however, applies only when the defendant himself takes the stand. The Supreme Court held in James v. Illinois (1990) that the prosecutor may not use unconstitutionally obtained evidence to impeach the testimony of other defense witnesses.
The exclusionary rule typically extends not only to the evidence found during an unconstitutional search, but also to evidence that is discovered because of the illegal search. Thus, if the police enter a house unconstitutionally and find drugs and a letter indicating where other drugs could be found, both the letter and the drugs at that house would be excluded because they were found during an unconstitutional search. But what if the police then go to the place referenced in the letter and find the other stash of drugs? Are those drugs admissible? The general answer is no, because those drugs are ‘‘fruit of the poisonous tree,’’ that is, they were found as the result of unconstitutional police action, and they too must be excluded.
Like all the other aspects of the exclusionary rule, however, this one has exceptions. First, if the police discover the evidence illegally but then their investigation takes them to the same evidence without violating the Constitution, they have established an ‘‘independent source’’ for the evidence—independent, that is, from the constitutional violation—and the evidence will be admitted (Murray v. United States ). Second, if the police discover evidence unconstitutionally but can demonstrate that they would have discovered the same evidence had no constitutional violation occurred, the evidence will be admitted under the ‘‘inevitable discovery’’ exception (Nix v. Williams ). Third, if the unconstitutional police action is so removed from the acquisition of the evidence that ‘‘the deterrent effect of the exclusionary rule no longer justifies its cost,’’ the attenuation doctrine serves to admit the evidence (Wong Sun v. United States ). It is unclear when exactly a court will determine that there has been sufficient attenuation, but relevant factors include the amount of time elapsed between the unconstitutional action and the discovery of the evidence, and how flagrant the violation of the Constitution was. Additionally, if the suspect provided the evidence in a display of his own free will, or if the evidence consisted of another person’s testimony, a court is likely to find that the evidence was attenuated from the violation.
Although both the direct evidence traceable to a constitutional violation and the indirect ‘‘fruits’’ of that violation are ordinarily inadmissible in a trial of the person whose rights were violated, the exclusionary rule does not apply where the defendant is someone other than the person who was subject to an unconstitutional search or seizure. So, suppose the police unconstitutionally break in to A’s apartment, where they find drugs and a letter from B to A proposing a drug transaction. At trial, A will have the letter and the drugs suppressed because of the constitutional violation. B, however, will not be able to contest the admission of the evidence against him, because his rights were not violated; the police broke into A’s apartment and invaded A’s privacy, not B’s.
Although most observers are familiar with the exclusionary rule’s applicability to Fourth Amendment violations, the rule applies also to violations of the compulsory Self-Incrimination Clause of the Fifth Amendment. In fact, while the text of the Fourth Amendment makes no explicit mention of exclusion, the Fifth Amendment contains an exclusionary rule that does not require judicial construction. That amendment provides that ‘‘[n]o person . . . shall be compelled in any criminal case to be a witness against himself.’’ Accordingly, where a court, the police, or another agency of government compels a statement by a criminal defendant—where the statement is made involuntarily because of the threat of criminal sanctions or physical harm, for example—that statement may not be admitted at the defendant’s trial for any purpose. The amendment presupposes that coerced statements are inherently unreliable, and therefore it would harm the truth-seeking process of trials for such evidence to be admitted.
More controversial has been the Supreme Court’s decision in Miranda v. Arizona (1966), in which compulsion would be presumed if the defendant were subjected to custodial interrogation and he were not provided the now-famous Miranda warnings. Under Miranda, then, voluntary statements are subject to the exclusionary rule. Because such voluntary statements are reliable, however, the Supreme Court has held that they will be excluded only from the prosecution’s case-in-chief. In other words, when the prosecution puts forward its evidence that the defendant committed a crime, that evidence cannot include the un-Mirandized statement. If the defendant takes the stand and testifies in his own defense, however, and makes statements contradicting the excluded statement, then the prosecution can make use of the un- Mirandized statement. The Supreme Court has held that excluding evidence from the prosecution’s casein- chief is necessary to ensure that the police will not violate Miranda, but the Court is unwilling to apply the exclusionary rule to allow the defendant to lie on the stand, when the lie could be exposed by using the un-Mirandized statement.
A further controversy centers on the application of the exclusionary rule to evidence obtained as the result of a Miranda violation. Suppose a suspect is interrogated without Miranda warnings and makes a voluntary confession to a murder, in which he discloses the location of the murder weapon. The police then give the suspect the Miranda warnings and ask the suspect to repeat the confession, which he does. The first confession is excluded from the prosecution’s case-in-chief.
The protections in the Bill of Rights are written in lofty terms, guaranteeing freedoms and invoking ideals that continue to inspire us.The exclusionary rule is both an attempt to realize those ideals and to take account of the practical necessities of investigating, prosecuting, and punishing crime. As a result, the doctrine is a hodgepodge of conflicting decisions and will remain so as long as the country continues to debate the price that it is willing to pay to protect its civil liberties.
References and Further Reading
Cases and Statutes Cited
See also Bivens v. Six Unknown Named Agents of Federal Bureau of Narcotics, 403 U.S. 388 (1971); Search (General Definition); Seizure