the name commonly given to the principle that evidence obtained by the government in violation of a defendant’s constitutional right may not be used against him. A defendant may prevent the prosecution from using evidence against her by making a “motion to suppress” before trial asking the judge to rule that the evidence is inadmissible. Physical evidence, confessions, or line-up identifications are all subject to exclusion if obtained in violation of a defendant’s constitutional right. The term exclusionary rule usually refers, however, to suppression of physical evidence that has been seized by the police in violation of a defendant’s *Fourth Amendment right not to be subjected to an unreasonable search or seizure. (See search warrant rules, exceptions to.) The Burger and Rehnquist Courts have substantially curtailed the degree to which the exclusionary principle actually operates as a “rule.” This curtailment reflects a fundamental redefinition of the character and purpose of the rule.

“Principled” Origin.

The framers of the Fourth Amendment had no reason to consider exclusion as a remedy for an unconstitutional search because they did not regard misconduct by a peace officer as a form of governmental illegality. Rather, misconduct by an officer was understood to be only a personal trespass that was subject to a civil lawsuit for damages. However, as police officers were given discretionary arrest and search authority during the nineteenth century, that early understanding of officer misconduct became increasingly unrealistic, and trespass actions against officers proved less effective as a remedy for unlawful arrests and searches.

The exclusionary rule was created in *Weeks v. United States (1914), in which the Supreme Court concluded, for the first time, that a federal marshal’s warrantless search of a residence in which illegal lottery tickets were seized was a violation of the Fourth Amendment. Because the marshal’s search was unconstitutional, the Court ruled that it was also unconstitutional for a federal court to receive the lottery tickets as evidence when Weeks was prosecuted for sending lottery tickets in the mail. Justice William *Day’s opinion for a unanimous Court concluded that the trial court’s decision to allow the documents to be used in the defendant’s trial was “a denial of the constitutional rights of the accused” and that the trial court had no authority to allow unconstitutionally seized evidence to be admitted at trial (p. 398).

The Weeks Court was writing on a nearly blank slate regarding the law of search and seizure. Like the other provisions of the *Bill of Rights, the Fourth Amendment does not spell out the consequences if the right that it announces is violated. Prior to Weeks, a violation of a defendant’s Fourth Amendment rights was inconsequential, so a defendant had no reason to challenge the constitutionality of a police search. Thus, courts had no occasion to spell out Fourth Amendment standards, and search law remained undeveloped. Only when the exclusionary rule was created was the Court presented with opportunities to pronounce Fourth Amendment search standards.

The Weeks opinion does not explain the theoretical basis for the exclusionary principle in detail. Read in the context of the formalist jurisprudence of the time, however—especially as reflected in the Court’s decision in *Boyd v. United States (1886)—it is clear that the exclusionary principle derives from the constitutional concept of limited governmental power. Weeks posits that a search that exceeds the constitutional authority of law enforcement officials must be deemed null and void and treated accordingly. If the government had no authority to seize the evidence, then a court—another branch of government—had no “right” to retain the evidence for use in a trial either. In keeping with the principled nature of the Weeks rationale, exclusion was the rule for unconstitutionally seized evidence in the federal courts for several decades. As Justice Oliver (p. 306) Wendell *Holmes wrote in Silverthorne Lumber Co. v. United States (1920), the point of the exclusionary principle was that unconstitutionally seized evidence “shall not be used at all” (p. 392). The only significant limitation on the rule’s operation in the years following Weeks was a *“standing” requirement, developed by lower federal courts, which prevented a defendant from challenging a search that did not violate his or her own personal *privacy (e.g., a defendant cannot usually challenge the constitutionality of a search of another person’s house, even if that search produced evidence that incriminated the defendant).

Extension to State Proceedings.

At the time of Weeks, the *Bill of Rights was construed to apply only to the federal government, and Weeks explicitly stated that its rule did not apply to searches by state police officers. In the years following Weeks, a number of *state courts considered whether to create state exclusionary rules on their own. Some did; a greater number did not. The arguments in the state debates over the rule mirrored the debate over Weeks itself. Critics of the rule said it served no purpose—suppression of evidence did not, in fact, punish the offending police officer—but its operation was costly to society because criminals were released. As Justice (then New York judge) Benjamin *Cardozo put it: “The criminal goes free because the constable has blundered” (People v. Defore, 1926). Critics of the rule suggested that alternative remedies for arbitrary searches—such as suits for damages or administrative sanctions against the offending police officers—would be more effective than the rule. Defenders of the rule expressed doubts regarding the availability or efficacy of these alternatives and argued that the rule was the only practical way to give meaning to the privacy right protected by the Fourth Amendment.

The issue of whether the Weeks rule should be applied to the states was reopened when the Court began to construe the degree to which the Fourteenth Amendment’s *Due Process Clause protected the rights of defendants in state criminal cases. In *Wolf v. Colorado (1949), Justice Felix *Frankfurter wrote for a 5 to 4 majority that, although the concept of due process does include some degree of protection from arbitrary government searches, that protection is not as extensive as the standards of the Fourth Amendment. Therefore, he concluded that the states were not required to apply the Weeks rule; rather they were free to address the problem of arbitrary police searches through any of a variety of alternative remedies.

After Wolf, a “*silver platter” doctrine allowed evidence seized by state officers to be admitted in federal trials, even though the searches violated Fourth Amendment standards. A decade later a 5 to 4 majority of the Court rejected the silver platter doctrine in Elkins v. United States (1960). Justice Potter *Stewart’s majority opinion asserted that the protections provided by the Fourth and *Fourteenth Amendments against unreasonable searches were equivalent, thus repudiating the basis for Wolf ’s refusal to extend the exclusionary rule to the states. In the very next term, in *Mapp v. Ohio (1961), five justices voted that the states were also required to apply the Weeks exclusionary rule. Justice Tom *Clark’s *plurality opinion reiterated the Weeks position that the rule is part of a defendant’s Fourth Amendment right, but he also argued that the rule was needed because the states had not developed any meaningful alternative remedies for arbitrary searches in the decade since Wolf.

Mapp’s application of the rule to state prosecutions had the effect of extending Fourth Amendment protections to a much larger and more diverse set of defendants than the white-collar criminals or tax evaders often found in federal prosecutions. Perhaps for that reason, Mapp generated far more political controversy than Weeks had. In particular, Mapp was denounced by police administrators and politicians for “handcuffing” the police.

Deterrence Rationale.

Much of the controversy over Mapp focused on the practical effects of the rule. Defenders of the decision such as Professor Yale Kamisar argued that it had finally caused police departments to begin to train officers about search standards. Critics of the rule such as Professor Dallin Oaks responded that the rule could not affect police behavior because suppression of evidence did not directly punish offending officers. They also argued that the rule was not constitutionally required but was really only a judge-made, instrumental policy aimed at deterring future police misconduct. Because the critics believed that the rule failed as a deterrent, they argued that it should be abandoned as soon as another remedy for unconstitutional searches could be put in place. Thus, what has come to be known as the “deterrence rationale” for the exclusionary rule paradoxically opened up possibilities for attacking, limiting, or even abolishing it.

The deterrence rationale took on increased importance when President Richard *Nixon named four justices to the Court—including Chief Justice Warren *Burger, an outspoken critic of the rule—who were inclined to favor law enforcement interests. In United States v. Calandra (1974), the Court fundamentally redefined the rule’s purpose, substituting the deterrence rationale for the previous principled formulation of the rule in Weeks. Justice Lewis *Powell’s opinion for the six-justice (p. 307) majority repudiated the idea that the exclusionary rule was a constitutional right of a defendant who was the victim of an unconstitutional search. It was, he said, merely a prophylactic measure rather than a constitutional rule. Powell asserted that violation of the Fourth Amendment by an unconstitutional search is “fully accomplished” when the search ends and that the admission of unconstitutionally seized evidence in a later trial “work[s] no new Fourth Amendment wrong” (p. 354). Instead, Powell declared that “the rule’s prime purpose is to deter future unlawful police conduct” (p. 347).

Powell’s Calandra opinion also reasoned that because the rule was intended only to deter, the test for whether it should be applied in a particular setting should be to weigh the “deterrent benefits” of applying the rule against the social “costs” of its operation. In Calandra, the Court decided that the exclusionary rule would not be applied to evidence in *grand jury proceedings because exclusion in that setting would not produce any significant increment of deterrence.

Although Calandra only limited the rule’s operation, the adoption of a “costs and benefits” approach was widely thought to have positioned the Court to abolish the exclusionary rule on the ground that it generally failed as a deterrent. As it turned out, however, persuasive empirical data about the rule’s effectiveness as a deterrent proved to be unavailable. In a pair of 1976 decisions, *Stone v. Powell and United States v. Janis, the Court substituted speculation for the unobtainable data, and announced that from that point forward it would assume the rule is effective as a deterrent when evidence is excluded from the prosecutor’s case in chief at trial, but that it was doubtful exclusion in other settings would create any significant “incremental deterrent effect” (Stone v. Powell, p. 493). Although the Court had decided not to abolish the rule entirely (it may be significant that no alternative means of enforcing search standards has ever emerged), this approach to the rule’s deterrent effect allowed the Court to curtail sharply the scope of its application. The Court has invoked costs and benefits analysis to admit unconstitutionally seized evidence in civil cases and in deportation hearings, in addition to grand jury proceedings; it has also allowed unconstitutionally seized evidence to be used liberally to impeach a defendant’s testimony at trial (which may effectively prevent defendants who have succeeded in having evidence suppressed from testifying); and it has also limited review of state court search rulings through federal *habeas corpus proceedings. Meanwhile, lower courts have invoked costs and benefits logic to admit unconstitutionally seized evidence in sentencing and probation or parole revocation hearings—among the most common proceedings in criminal prosecutions.

Exceptions.

The Burger and Rehnquist Courts have also limited the operation of the rule by creating several new exceptions that allow the prosecutor unlimited use of unconstitutionally seized evidence, even in his or her case in chief at trial. One exception, announced in Nix v. Williams (1984), allows the use of unconstitutionally seized evidence, if, hypothetically, the police would have “inevitably discovered” the evidence even if the unconstitutional search had not occurred (p. 441). The Court created another exception (commonly but inaccurately called a *“good-faith exception”) in United States v. *Leon (1984), which allows the use of evidence that was seized in a search conducted pursuant to an unconstitutionally issued search warrant. There the Court reasoned that a defective warrant is the fault of the magistrate who issued it rather than the police officers who searched; thus, suppressing the evidence would not affect police conduct. A parallel exception, created in Illinois v. Krull (1987), allows the use of evidence seized by police who conducted a search pursuant to an unconstitutional statute. Another exception, created in Arizona v. Evans (1995), allows the use of evidence unlawfully seized by police because of faulty court records.

The exclusionary rule today is a shadow of that envisioned in Weeks. Ironically, the “deterrence rationale” has been invoked to permit so many uses of unconstitutionally seized evidence that the rule’s efficacy as a deterrent may well be diminished. Certainly, unconstitutionally seized evidence can often be used to the government’s advantage. It also appears that the rule is less “costly” than has often been assumed. A 1983 study by Thomas Davies that was discussed in the Leon opinions estimates that only between 0.6 and 2.35 percent of all felony arrests are “lost” at any stage in the arrest disposition process (including trials and appeals) because of the operation of the exclusionary rule. The rate of lost arrests is somewhat higher in drug and other possessory offenses, but much lower in violent crimes. Thus, the continuing debate over exclusion would appear to be fueled as much by the ideological commitments of the participants as by the effects the rule now exerts on the criminal justice system.

Thomas Y. Davies, “A Hard Look at What We Know (and Still Need to Learn) About the ‘Costs’ of the Exclusionary Rule,” American Bar Foundation Research Journal (1983): 611–690. Thomas Y. Davies, “Recovering the Original Fourth Amendment,” Michigan Law Review 98 (1999): 547–750. Yale Kamisar, “Does (Did) (Should) the Exclusionary Rule Rest on a ‘Principled Basis’ Rather (p. 308) Than an ‘Empirical Proposition’?” Creighton Law Review 16 (1983): 565–667. Yale Kamisar, “The Writings of John Barker Waite and Thomas Davies on the Search and Seizure Exclusionary Rule,” Michigan Law Review 100 (2002): 1821–1866. Dallin H. Oaks, “Studying the Exclusionary Rule in Search and Seizure,” The University of Chicago Law Review 37 (1970): 665–757. Christopher Slobogin, “Why Liberals Should Chuck the Exclusionary Rule,” University of Illinois Law Review 1999 (1999): 363–446. Potter Stewart, “The Road to Mapp v. Ohio and Beyond: The Origins, Development and Future of the Exclusionary Rule in Search and Seizure Cases,” Columbia Law Review 83 (1983): 1365–1404.

Thomas Y. Davies