The exclusionary rule permits a criminal defendant to prevent the prosecution from introducing at trial otherwise admissible evidence that was obtained in violation of the Constitution. In a sense the term "exclusionary rule" is misleading, because there are many exclusionary rules. Some, such as the rule against hearsay, exclude evidence because it is not very reliable. Others, such as a rule prohibiting a witness from testifying if the calling party did not disclose the witness before trial, are sanctions for the failure to comply with a nonconstitutional rule.
While every legal system excludes some evidence deemed irrelevant or untrustworthy, the constitutional exclusionary rule is unusual in rejecting highly probative evidence, often with the consequence of nullifying a meritorious prosecution. It is therefore not surprising that the exclusionary rule has occasioned sustained and sometimes bitter controversy.
A simple example helps to explain both the practical operation, and the controversial nature, of the exclusionary rule. Suppose the police stop a driver for speeding, and in the course of issuing the citation they discover cocaine in the glove compartment of the car. If the defendant did not consent to the search, and if the police did not have probable cause to believe illegal drugs could be found in the glove compartment, the search would be illegal under the Fourth Amendment.
To invoke the exclusionary rule the defendant would move before trial to suppress the drugs as illegally seized. This motion would be decided by a judge sitting without a jury. The defense would have the burden of proving that the defendant's rights were violated. If the facts are disputed (as they usually are), the parties would be allowed to call witnesses. If the accused testifies at the suppression hearing, this testimony is not admissible against him at a later trial.
If the judge decides that the search was illegal, the exclusionary rule comes into play and the evidence will be suppressed in the pending case. In our example, the government has no case without the drugs, and the court would have to dismiss the charge. Note that the defendant who moves to suppress incriminating evidence is usually in fact guilty. Maybe the driver had no idea that someone else had put cocaine in the glove box, or maybe the officer planted it, but the most likely hypothesis is that when there is physical evidence to be suppressed the person seeking suppression is indeed guilty as charged.
Note also that the rule does not automatically result in acquittal. Suppose the police found cocaine in both the glove compartment and the trunk, and the court ruled that the cocaine in the trunk was seized illegally but that the search of the glove compartment was legal. The suppression of the cocaine from the trunk would not protect the defendant from being convicted for possessing the cocaine in the glove compartment.
Note, finally, that the rule does not require returning contraband to the defendant. If the evidence at issue were lawful to possess, such as a diary or a properly registered firearm, the defendant would be entitled to its return at the close of the proceedings. Even when contraband is illegally seized, however, the defendant is entitled only to its exclusion from evidence, not to its return. Were it otherwise the defendant could be arrested on the courthouse steps for possessing the returned contraband.
If the judge grants the motion to suppress, the government would be allowed to appeal before a verdict is entered on the pending charge. Otherwise, the double jeopardy clause would bar appellate review of the trial court's decision to grant the suppression motion. If the judge decides that the evidence was not seized illegally, the motion will be denied and the case will be set for trial. If the defendant is convicted, he will be free to appeal on the ground that the trial court should have granted the motion to suppress.
Why does the law permit the guilty to escape justice because the police violated the Constitution? Would it not make more sense to admit the evidence and punish the police by demotion or suspension, or through civil lawsuits? The standard explanation is that these alternative remedies for constitutional violations have been found, in practice, to be ineffectual. Law enforcement agencies have not shown the willingness to discipline officers whose excesses lead to successful prosecutions. In civil suits against the police, the damages juries might return for illegal searches, together with the good-faith immunity defense available to the police, have blunted the deterrent force of the tort remedy. Freeing the guilty is not very appealing, but doing nothing about violations of the Constitution has seemed even worse.
Origins and development of the rule
The history of the rule reflects this ambivalence. The common law did not allow the exclusion of evidence on account of irregularities in the way in which a party acquired it. Instead, a citizen wronged by an illegal search could sue the wrongdoers for the tort of trespass. Anyone who invaded another's property was guilty of trespass and had to pay damages, unless the intruder had some positive legal authority such as a valid warrant. The framers of the Fourth Amendment included the warrant clause to prevent the new government from cutting off the trespass remedy by issuing general warrants—one of the abuses that had incited the revolution.
A decline in the efficacy of the tort remedy coincided with the development of modern police forces in the mid–nineteenth century. Typically the police did not (and do not) target the rich and powerful for intrusive investigations. The generally poor, generally uneducated, and often minority-race victims of illegal searches were in a poor position to recruit lawyers to bring suits; they certainly could not count on generous jury verdicts against the police.
The Supreme Court recognized the exclusionary rule early in the twentieth century. Although the Fourth Amendment exclusionary rule may have arisen from the then-prevailing view that the Fifth Amendment privilege against self-incrimination shielded individuals from having their own property used against them as evidence, the early cases soon recognized a Fourth Amendment right to suppress illegally seized evidence even when the party invoking the rule had no Fifth Amendment rights (i.e., a corporation) and even when the evidence to be suppressed was illegal to possess at all.
The early cases, however, were limited to federal prosecutions. Criminal law enforcement in the United States is primarily the responsibility of state, rather than federal, officers. Some state courts followed the Supreme Court's lead and adopted the exclusionary rule; others adhered to the common law rule admitting evidence without regard to how it was obtained. Two of the past century's most celebrated American jurists wrote opposing opinions on the issue during this period. A good way to begin thinking about the exclusionary rule is to compare Judge Benjamin Cardozo's opinion for the New York Court of Appeals in People v. Defore, 150 N.E. 585 (N.Y. 1926), refusing to adopt the exclusionary rule, with Justice Roger Traynor's opinion for the Supreme Court of California in People v. Cahan, 282 P.2d 905 (Cal. 1955), adopting the exclusionary rule.
Not until 1961, in the watershed case of Mapp v. Ohio, 367 U.S. 643 (1961), did the Supreme Court hold that the exclusionary rule applies to the states as a matter of Fourteenth Amendment due process. In states that had not followed the exclusionary rule on their own prior to Mapp, the Mapp decision had a dramatic impact. Warrant use in major cities went from a handful to hundreds per year; search-and-seizure law became the subject of police training programs. These developments would not have occurred if the tort remedy had been an effective deterrent. Had the tort remedy been effective, the police in states without the exclusionary rule would have been using warrants and training their officers in constitutional law all along.
Even the liberal Warren Court, however, was reluctant to free the guilty. As soon as the rule applied to the states, where crimes of violence are typically prosecuted and where the great majority of prosecutions for all types of offenses are brought, the Court began to adopt narrower interpretations of substantive Fourth Amendment rights, and to recognize exceptions to the exclusionary remedy. For example, shortly after Mapp the Court excluded undercover operations from any scrutiny whatsoever under the Fourth Amendment; refused to apply Mapp to free prisoners previously convicted by illegally obtained evidence; and reaffirmed the rule that only the search victim can invoke the rule, even when the evidence incriminates others.
As the Court grew more conservative during the 1970s (as it has remained ever since), the exceptions to the exclusionary rule have threatened to swallow the rule. Illegally obtained evidence is now admissible in the following situations:
- in the government's case at trial against any person whose rights were not violated by the illegal search;
- in the government's case at trial if the officers who committed the illegal search were acting in reasonable, good-faith reliance on a warrant, a statute, or a court record later determined to be unconstitutional or erroneous;
- in the government's case at trial, if the government can prove that the evidence would have been discovered inevitably in the absence of the illegality;
- in the government's case at trial, if the illegal police conduct led to the evidence only by an attenuated chain of events;
- to impeach the defendant's testimony, if he chooses to take the stand at trial;
- in preliminary and collateral proceedings, such as before the grand jury.
In deciding these cases the Court has regarded deterring future police misconduct as the sole reason for the rule. When weighing the desirability of an exception, the Court has explicitly balanced the likely deterrent benefits against the apparent costs of freeing the guilty. Although this approach has usually favored the prosecution, the Court has at least once found that the balancing test requires a narrower, rather than a broader, interpretation of the exceptions. In that case, the Court held that the impeachment exception did not allow the use of tainted evidence to contradict the testimony of a third-party witness for the defense, as distinct from the testimony of the defendant himself.
In the main, however, the balance has clearly inclined in favor of the government. One dramatic illustration is the good-faith exception recognized for searches conducted pursuant to facially-valid warrants recognized in United States v. Leon, 468 U.S. 897 (1984). Because the police enjoy good-faith immunity from tort suits, withholding the exclusionary rule leaves no apparent remedy when the police obtain a warrant without showing probable cause. The Fourth Amendment flatly declares that "no warrants shall issue, but upon probable cause." The good-faith exception means that when warrants do issue without probable cause, neither exclusion of the fruits, nor civil liability, follows from the violation.
As the Court has come to focus exclusively on deterrence in applying the rule, some legal scholars have argued that illegally obtained evidence should be suppressed without regard to deterrence. It is claimed, for instance, that excluding tainted evidence is necessary to preserve judicial integrity, or to vindicate the principle of judicial review. The challenge confronting all such nondeterrent theories of exclusion is to connect the search for, and the use of, the evidence, even when the courts impose a sanction adequate to deter future violations.
This connection is not immediately apparent. Suppose the police discover narcotics at the home of A pursuant to a valid warrant, and an identical lot of drugs in the home of B but without a warrant. There does not seem to be any normative distinction in favor of B. We do not want the police in future cases to search without warrants, so we might exclude the evidence against B to prevent searches of completely innocent persons in other cases. But we would not say that B has a personal right to exclusion divorced from future consequences.
Suppose instead that the police, without a warrant, search the home of C and discover nothing incriminating. If exclusion were thought of as a personal right, the innocent C would have less protection against unreasonable searches than the guilty B. The Fourth Amendment is not generally regarded as conferring substantive immunity for crimes committed in private. So long as that judgment stands, connecting the search and the use of the evidence will be difficult. Given that innocent search victims possessed no evidence a court could later exclude, exclusion would not seem to be an indispensable remedy. What is indispensable is some effective deterrent against future violations. The Supreme Court has been willing to require the exclusionary rule until such time as Congress or the states establish an effective alternative.
A jurisdiction that adopted and enforced an effective alternative deterrent to police misconduct would have a strong case for abolishing the exclusionary rule. If, for instance, police who engaged in illegal searches were suspended for a year without pay for the first infraction, and terminated for a second, and if this policy were monitored and enforced effectively, there would be few illegal searches and no need for the further deterrent of the exclusionary rule. Note, however, that under such a system, the public would lose the same evidence as the exclusionary rule suppresses, because it would never be discovered in the first place. Note also that under such a regime the exclusionary rule would not be particularly unpopular because it would only rarely come into play, as the administrative disciplinary system would prevent most illegal searches from ever taking place. Perhaps because of these considerations, no jurisdiction in the United States has adopted strict administrative, tort, or criminal sanctions for illegal searches.
Even if deterrence is the key to the rule, it hardly follows that the Court has assessed the costs and benefits of exclusion correctly. For example, preventing persons other than the search victim to invoke the exclusionary rule goes a long way toward undermining the rule's deterrent threat. In some cases the police deliberately target third-party custodians of evidence for illegal searches, knowing that the target of the investigation will not be allowed to challenge the legality of the search. More commonly, law enforcement agents investigating a conspiracy know that many of the conspirators will not have standing to challenge the search or arrest of one of their number. The standing exception seems more like a convenient way to escape the substantive limits of the Fourth Amendment than a reasoned exposition of a deterrent theory of the exclusionary rule.
Moreover, each exception to the exclusionary rule recognized by the Court reduces the sanction imposed on the government for illegal searches and seizures. Standing alone, the impeachment exception or the inevitable discovery exception might do little damage to deterrence. Given all the exceptions together, however, the disincentive to conduct illegal searches has been significantly reduced.
Despite the various exceptions, the exclusionary rule lives on, thirty years after Warren Burger replaced Earl Warren as Chief Justice. Even conservative justices have been unwilling to abolish the rule, just as even liberal judges recognized some exceptions. The exceptions reflect the reluctance to release patently guilty offenders; the persistence of the rule reflects the reluctance to provide no effective remedy for violations of the Constitution.
The policy debate
Is the exclusionary rule justifiable? To put this question in context we must qualify the question by adding another: "Compared to what?" Defenders of the exclusionary rule rely heavily on the inadequacy of other remedies. If the constitution requires some effective remedy for violations, and if tort and administrative remedies have proved inadequate in practice, there is a strong case for requiring exclusion.
Critics have made a variety of objections to the rule. They argue that:
- exclusion is costly inasmuch as it requires freeing guilty offenders;
- that the rule does nothing for innocent victims of police misconduct, who have no evidence of crime to be suppressed;
- that the rule's deterrent benefits are, as an empirical matter, doubtful;
- that, if the rule does deter, it may overdeter by causing the police not to engage in searches that, although close to the line of illegality, are not over that line;
- that the tort remedy might be made more effective by plausible reforms;
- that exclusion causes police perjury, tolerance of police perjury by judges, and narrow interpretations of substantive Fourth Amendment rights by judges reluctant to free the guilty.
With respect to the cost associated with freeing the guilty, defenders of exclusion reply that any effective remedy for Fourth Amendment violations would result in the escape of guilty criminals. If the tort remedy, for example, were made a credible deterrent, fear of tort liability would cause the police to refrain from illegal searches. Since some illegal searches would reveal evidence of crime, alternative remedies would have the same costs as the exclusionary rule, in precise proportion to their effectiveness in deterring police misconduct.
In some cases, however, exclusion does cost the public a conviction that might have been obtained without violating the Constitution. If the police, having probable cause, decline to seek a warrant when one would have been issued, the suppression of the evidence prevents the police from obtaining it lawfully. A large majority of reported offenses, however, are never cleared by the police, so that it seems fair to assume that absent the illegality the police would not have come by the evidence lawfully. Drug cases, which involve offenses that would not be reported by a complaining witness, are even less likely to have been made lawfully. In those cases in which the prosecution can prove that the police would have obtained the evidence lawfully absent the illegality, the inevitable discovery exception allows the admission of the evidence. On the whole it seems fair to say that although the exclusionary rule may abort a few prosecutions the Constitution permits, the "cost" of freeing guilty criminals is for the most part attributable to the substantive constitutional rights that limit police power to search for evidence, rather than to the remedy used to deter future violations of those limits.
Indeed, an effective tort remedy might well overdeter the police, in the sense that officers fearful of personal liability might pass by lawful but borderline searches that might lead to the conviction of the guilty. Imposing tort liability on the police department or the municipality would create similar incentives on the part of police supervisors, who might train their officers to act conservatively out of fear of liability.
Defenders of the exclusionary rule admit that the rule does not provide any direct relief for innocent victims of police misconduct. Proponents of exclusion point out that if the rule deters, it will protect innocent citizens in future cases, although police motivated by sadism or racism rather than the desire to secure convictions will be unimpressed by the threat of exclusion. Because any effective deterrent will benefit guilty and innocent alike in future cases, tort remedies have an advantage over exclusion only to the extent that they compensate innocent victims, which exclusion clearly fails to accomplish. But so long as the tort remedies are ineffective, they fail to compensate the great majority of innocent search victims.
With respect to the empirical issue of the rule's deterrent effect on police behavior, proponents of the rule point to the following evidence. First, all modern studies find that the suppression of evidence is quite rare, involving perhaps 1 percent of felony cases (and in many of these cases the defendant may still be convicted on the force of untainted evidence). If evidence is only rarely suppressed, the argument goes, the police must be complying with constitutional standards. If, however, the rate of suppression is low because of successful police perjury or trial court hostility to freeing the guilty, there is no inconsistency between a low suppression rate and a low compliance rate.
Exclusionary rule proponents also point to the dramatic increase in warrant use that followed Mapp v. Ohio in those states whose courts had not adopted the exclusionary rule on their own. The increase is hard to explain except as deterrence in operation, because while other factors might have spurred the police to increase the frequency of searches, there was no practical reason for them to obtain search warrants except for the Supreme Court's decision in Mapp. Exclusionary rule proponents also point out that the police now devote considerable time to training officers in constitutional standards, to educating the force about new judicial developments, and to developing tactics that work around constitutional rules announced by the courts. Each of these phenomena is consistent with the hypothesis that the exclusionary rule deters. On the whole it seems fair to say that the exclusionary rule does influence police behavior, but that the extent of that influence is open to reasonable dispute.
Indeed, some commentators have taken the position that the exclusionary rule overdeters, reasoning that because the social cost of illegal searches is modest (the criminal's interest in escaping just punishment is not, on this view, a cost at all), and the loss of good cases is a substantial penalty on the police, that the police will be discouraged from aggressive action. If, however, it is true that the cost of lost convictions is attributable to the Fourth Amendment itself, not to the exclusionary remedy, the imbalance between the social costs and benefits of illegal searches disappears. Optimal deterrence comes from setting the sanction equal to the wrongdoer's expected gain discounted by the probability of escaping the sanction. Because the primary motive for illegal searches is successful prosecution, the rule comes close to setting the sanction equal to the government's anticipated gain. Indeed, from a strictly economic point of view, the rule may underdeter, because even when tainted evidence is suppressed the police still succeed in taking contraband off the street and acquiring information about criminal operations. Police therefore sometimes retain an incentive to search illegally even if they are certain that the fruits will be excluded.
Critics of the exclusionary rule usually admit that existing tort remedies are ineffective. They have proposed various reforms to make the tort remedy a more formidable deterrent. Among the more common suggestions are imposing liability on police departments and municipalities, assessing liquidated or punitive damages, and curtailing or abolishing good-faith immunity defenses. Whether reforms such as these could convert the tort remedy into an effective deterrent is a debated, but probably purely academic, point. Neither courts nor legislatures have embraced the reform proposals, even though they have appeared from prominent quarters in a steady stream for more than fifty years.
There are two major reasons for this failure. First, as a political matter, making it easier to sue the police at the expense of the taxpayer is not an attractive proposition to typical legislators. The beneficiaries of such a proposal are the likely targets of police excess, that is, young men, disproportionately black. The potential losers are those who might be protected from predatory crime by police disregard of constitutional standards. The latter group is more numerous and more influential than the former.
Second, on the merits, there is the standing risk that a tort remedy might set the sanction for Fourth Amendment violations higher than the social costs attending the violation, and thus inhibit justifiable as well as unjustifiable police actions. There is some evidence that officials exaggerate their exposure to liability. The police themselves seem to prefer exclusion to personal liability.
Evaluating the damages for Fourth Amendment violations is quite difficult. Should the victim of an arrest without probable cause recover the value of the lost time (say, thirty dollars an hour for the ten hours between arrest and release?) or ten thousand dollars for the arbitrary and degrading deprivation of personal liberty? Should the homeowner subjected to a warrantless search be awarded the price of new hinges and one visit from a cleaning service, or ten thousand dollars or more for invasion of privacy?
Even if broad agreement existed on the compensatory aspect of tort damages, the deterrent aspect poses further problems. What amount suffices to deter future illegal, but not future legal, arrests and searches? Set too high and damages would discourage legitimate police work; set too low and they would put constitutional rights up for sale at bargain prices. One advantage of the exclusionary rule is that it sets the sanction roughly equal to the government's expected gain, thereby approximating the sanction suggested by optimal deterrence theory.
The question whether alternative remedies might be made effective largely subsumes another issue sometimes raised about the exclusionary rule. Prior to Mapp v. Ohio relatively little substantive Fourth Amendment law was established, because many jurisdictions had no exclusionary rule and because few tort suits were brought. Since Mapp the Supreme Court alone has decided dozens if not hundreds of Fourth Amendment cases. While uncertainties and confusion still surround some issues, the law has become better defined as a result.
Some defenders of the exclusionary rule point out that without the rule, there would be no procedural vehicle for establishing or changing the substantive law. This is a strong point against simple abolition of the rule. But if an effective tort remedy replaced the exclusionary rule, and if damages were generous enough to encourage suits, the tort system would provide a new procedural forum for shaping substantive Fourth Amendment law.
There is growing recognition that some police officers will commit perjury to avoid the suppression of evidence. The extent of the phenomenon is necessarily conjectural. If the reason why suppression motions rarely succeed is that the police violate the applicable rules and then successfully lie about it later, the exclusionary rule would not have accomplished very much.
Widespread perjury is by no means inconsistent with widespread compliance. Proponents of the rule believe that the training programs and changes in police culture fostered by Mapp reduce the occasions in which the police violate the applicable law in the first instance, even if some officers are willing to lie on the stand after it becomes clear that the discovery of the evidence was illegal. Police testimony could be subjected to more searching scrutiny, by such measures as evidentiary presumptions against consent to search or the admissibility of polygraph evidence at suppression hearings. Finally, it is worth noting that tort remedies, which might expose police departments or individual officers to substantial financial liabilities, would be more likely to transfer police perjury from the criminal to the civil courts than to reduce its prevalence.
Other constitutional exclusionary rules
Thus far we have concentrated on the exclusion of evidence obtained in violation of the Fourth Amendment. Sometimes, however, the police obtain evidence in violation of other constitutional provisions. For example, the Fifth Amendment privilege against self-incrimination can be overcome by a grant of official immunity. When a witness testifies before a grand jury or a legislative committee under an immunity order, the subsequent testimony may not be used at a subsequent criminal prosecution of the witness. Nor can the government use other evidence derived from the immunized testimony. The burden is on the government to prove that the additional evidence was obtained independently of the compelled testimony. If, at a subsequent trial, the previously immunized witness takes the stand and testifies inconsistently with the prior immunized testimony, the immunized testimony may not be admitted even for impeachment.
By contrast, although the famous warnings required by Miranda v. Arizona are premised on the Fifth Amendment privilege against self-incrimination, the Miranda exclusionary rule operates more like the Fourth than the Fifth Amendment exclusionary rule. Statements obtained in violation of Miranda v. Arizona are admissible to impeach, and other evidence derived from such statements is often admitted when the causal connection between the violation and the discovery of the evidence is attenuated. Although the Supreme Court recently reaffirmed the constitutional basis of the Miranda rules, the Court stopped short of equating Miranda violations with compelled testimony.
Before Miranda, the Supreme Court had established a due process test excluding confessions obtained by brutal or coercive police methods. The due process test remains as a supplement to Miranda. Because coerced confessions are thought to be both less reliable, and more offensive, than admissions obtained in violation of Miranda, a stricter exclusionary rule applies to coerced confessions. When a confession is actually coerced by brutality or other extreme forms of police pressure, the confession is not admissible even if the defendant at trial testifies inconsistently with the coerced admission.
The exclusion of eyewitness identification evidence obtained in violation of the Sixth Amendment right to counsel, or by unfair suggestiveness in violation of due process, differs from both the Fourth and Fifth Amendment context. Evidence of an unconstitutional pretrial lineup or photo identification procedure must be suppressed, but the witness will ordinarily be allowed to testify at the trial that she recognizes the defendant as the offender. The theory is that the witness's memory of the crime is independent of the pretrial lineup. Although highly doubtful in light of modern psychological research on identification, courts frequently allow the in-court identification, provided that the witness testifies that current memory is independent of the prior, tainted lineup or photo array. In this situation defense counsel sometimes introduces proof of the prior suggestive lineup (which counsel worked hard to have suppressed in the first place) as a necessary means to discredit the in-court identification.
Whether the exclusionary rule is an appropriate remedy for violations of the equal protection clause is an open question. If the police have probable cause to search or arrest a suspect, but the suspect can prove that the police were motivated by racial animus, there is a violation of the equal protection clause but not a violation of the Fourth Amendment. Some lower courts have considered whether such a suspect may suppress the fruits of the equal protection violation or if a damage action provides the exclusive remedy. It seems likely that the issue eventually will present itself to the Supreme Court.
Proposals for reform
Forty years have passed since Mapp v. Ohio. Outright abolition of the exclusionary rule has not yet occurred and seems extremely unlikely absent legislative creation of innovative alternative remedies. Since legislative reforms seem unlikely as well, the exclusionary rule appears to be with us for some time to come. While the argument has been made that abolition would force legislatures to adopt effective alternatives, the state experience prior to Mapp offers evidence to the contrary. Modifications of the rule's current operation, however, might be somewhat more likely.
By now the Supreme Court has embraced most pro-prosecution reforms of the exclusionary rule. Two that have not yet been recognized are a general good-faith exception and a comparative-reprehensibility rule. Thus far the Supreme Court has recognized a good-faith exception only when the police reasonably have relied on a warrant issued by a judge, on a statute passed by a legislature, or on a judicial record maintained by a clerk of the court. At least one circuit court of appeals has gone further, and held that even without statutory or judicial authorization, the exclusionary rule does not apply when illegal police conduct is the product of a reasonable good-faith mistake. Defenders of such a rule argue that police cannot be deterred from conduct they think is legal. Critics respond that the Fourth Amendment itself permits "reasonable" searches and seizures, and that incentives favoring prudence can deter negligence by police, just as negligence by doctors or drivers can be deterred.
The comparative-reprehensibility theory calls for considering the seriousness of the defendant's crimes and the officer's misconduct before excluding evidence. A turn to such a discretionary exclusionary rule has been criticized as inviting trial judges—often elected—to give the police a free hand in serious cases. The comparative-reprehensibility approach does not seem to have as much support as the general good-faith exception. As a matter of legal realism the seriousness of the offense and the extent of police wrongdoing will factor into the decision to some degree even without doctrinal authorization.
Commentators and dissenting justices have put forward a variety of pro-defense proposals. These include:
- target standing, permitting a third party to invoke the exclusionary rule when the third party was the target of the investigators who illegally searched the victim;
- a bad-faith exception to the other exceptions, so that when the police knew or should have known that their actions were illegal, the other exceptions would no longer apply;
- replacing all current exceptions with a single inevitable-lawful-discovery exception, such that if the government failed to prove that the evidence would have been discovered consistently with the Constitution no other exceptions would apply.
All of these reforms have strong support in the deterrence theory. Current Supreme Court precedent, however, rejects each of these approaches.
The exclusionary rule persists because there is no credible alternative. Freeing the guilty is unpalatable, and on many occasions the courts have sought to avoid that result by narrowing the substantive Fourth Amendment law or by recognizing exceptions to the exclusionary rule. But absent some other meaningful remedy, outright abolition of the exclusionary rule would, in the words of Justice Holmes, "reduce the Fourth Amendment to a form of words." The Supreme Court has not been willing to go that far.
Davies, Thomas Y. "A Hard Look at What We Know (and Still Need to Learn) about the Exclusionary Rule: The NIJ Study and Other Studies of 'Lost' Arrests." American Bar Foundation Research Journal (1983): 611.
Dripps, Donald A. "Living With Leon." Yale Law Journal 95 (1986): 906.
Foote, Caleb. "Tort Remedies for Police Violations of Individual Rights." Minnesota Law Review 39 (1955): 493.
Hall, Connor. "Letters of Interest to the Profession, Evidence and the Fourth Amendment." American Bar Association Journal 8 (1922): 646.
Kamisar, Yale. "Does (Did) (Should) the Exclusionary Rule Rest on a 'Principled Basis' Rather Than on an 'Empirical Proposition'?" Creighton Law Review 16 (1983): 565.
Orfield, Myron W., Jr. "Deterrence, Perjury, and the Heater Factor: An Exclusionary Rule in the Chicago Criminal Courts." University of Colorado Law Review 63 (1992): 75.
Schlesinger, Stephen R. Exclusionary Injustice. New York: M. Dekker, 1977.
Slobogin, Christopher. "Why Liberals Should Chuck the Exclusionary Rule." University of Illinois Law Review (1999): 363.
Stewart, Potter. "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.
Stuntz, William J. "The Virtue and Vices of the Exclusionary Rule." Harvard Journal of Law and Public Policy 20 (1997): 443.
Thomas, George C., and Pollack, Barry S. "Balancing the Fourth Amendment Scales: The Bad-Faith Exception to Exclusionary Rule Limitations." Hastings Law Journal 45 (1993): 21.
Mapp v. Ohio, 367 U.S. 643 (1961).
Miranda v. Arizona, 384 U.S. 436 (1966).
People v. Cahan, 282 P.2d 905 (Cal. 1955).
People v. Defore, 150 N.E. 585 (N.Y. 1926).
United States v. Leon, 468 U.S. 897 (1984).
When the police obtain evidence by violating the bill of rights, the victim of their misconduct may lack any effective legal remedy. Yet some enforcement mechanism is necessary if several important constitutional guarantees are to be a reality and not merely expressions of hope. The Supreme Court responded to this concern by developing a series of rules that have come to be known in the aggregate as the exclusionary rule. In typical application, the rule is that evidence obtained in violation of a person's constitutional rights cannot be used against that person in his or her trial for a criminal offense. The rule is most frequently applied to exclude evidence produced by searches or seizures made in violation of the fourth amendment. However, a coerced confession obtained in violation of the defendant's Fifth Amendment right against self-incrimination, or a statement taken from the defendant in violation of his Sixth Amendment's guarantee of the right to counsel, would also be inadmissible at his trial.
The term "exclusionary rule" is of modern origin, but even at common law a coerced confession was excluded or inadmissible as evidence, because its involuntariness cast serious doubt on its reliability. No one today seriously argues that this long-standing rule of evidence should be abandoned. Other aspects of the exclusionary rule, however, have been the source of major controversy among members of the judiciary, professional commentators, law enforcement officials, and the public.
The controversy did not become intense until the era of the warren court. But as far back as weeks v. united states (1914) the Supreme Court had unanimously held that evidence seized in violation of the Fourth Amendment was inadmissible in a federal criminal prosecution. However, even after the Court had held in wolf v. colorado (1949) that the Fourth Amendment's guarantee against unreasonable searches and seizures was applicable to the states, the Court had continued until 1961 to resist the argument that the exclusionary rule should also be extended to state prosecutions. In that year, in mapp v. ohio, the Warren Court held that the Fourteenth Amendment did, indeed, impose on the states the exclusionary rule derived from the Fourth Amendment. Subsequent decisions broadened the Sixth Amendment guarantee of the right to counsel to govern the procedures for police interrogation and for the use of lineups; each of these developments was accompanied by an extension of the exclusionary rule to state-court proceedings. Since the " fruit of the poisonous tree " doctrine requires the exclusion not only of evidence immediately obtained by these various forms of constitutional violation but also of other evidence derived from the initial violations, the exclusionary rule in its modern form results in the suppression of many items of evidence of unquestioned reliability and the acquittal of many persons who are guilty.
The primary purpose of the exclusionary rule, as the Supreme Court said in Elkins v. United States (1960), "is to deter—to compel respect for the constitutional guaranty in the only effectively available way—by removing the incentive to disregard it." Yet this deterrent function is only part of the exclusionary rule's justification. A court that allows the government to profit from unconstitutional police action sullies the judicial process itself, by becoming an accomplice in an unlawful course of conduct. When the Court first applied the rule in Mapp to state-court prosecutions, it said:
There are those who say, as did Justice (then Judge) [ benjamin n. ] cardozo, that under our constitutional exclusionary doctrine "the criminal is to go free because the constable has blundered." … In some cases this will undoubtedly be the result. But, …"there is another consideration—the imperative of judicial integrity." … The criminal goes free, if he must, but it is the law that sets him free. Nothing can destroy a government more quickly than its failure to observe its own laws, or worse, its disregard of the charter of its own existence. As Mr. Justice louis d. brandeis, dissenting, said: … "Our government is the potent, the omnipresent teacher. For good or for ill, it teaches the whole people by its example.… If the government becomes a lawbreaker, it breeds contempt for law."
The evidence seized in an illegal search—a knife, a packet of heroin, counterfeit plates—is as trustworthy and material as if the search had been lawful. The rule's critics argue that to protect the privacy of the search victim by letting a guilty person escape responsibility for his crime is illogical. It would make more sense, they say, to use the evidence (as do the courts in Great Britain, for example) and provide civil or criminal remedies against the errant police officers. If the rule's purpose is to deter police lawlessness, the critics argue, the rule misses the point: prosecutors, not police officers, feel the immediate effects of the rule. If the rule is designed to maintain respect for the courts, they ask how the public can be expected to respect a system that frees criminals by suppressing trustworthy evidence of their guilt.
How many criminals do go free when the constable blunders? Inadequate studies provide no clear-cut answer, except that opponents of the exclusionary rule grossly exaggerate the number of felons it sets loose, and they tend to dramatize the worst cases. In California, whose supreme court has created the most stringent exclusionary rule in the nation, a study by the National Institute of Justice showed that. 78 percent of all accused felons are not prosecuted because of search and seizure problems, and of those released, nearly three-fourths were involved in drug-related cases. The effect of the exclusionary rule is slight in cases involving violent crimes. When the charge is murder, rape, assault, or robbery, prosecutors decide not to proceed in one out of every 2,500 cases. Studies of felony court records in other states reach similar conclusions. Only 0.4 percent of all cases that federal prosecutors decide not to prosecute are rejected because of search problems. At the trial level, motions to suppress illegally seized evidence are rarely granted in cases of violent crime. If the exclusionary rule were abolished, the conviction rate in all felony cases would increase by less than half of one percent. Translated into absolute figures, however, thousands of accused felons are released nationally as a result of the exclusionary rule, most of them in drug and weapons possession cases. Street crime does not flourish, though, because of the exclusionary rule, even though it does protect criminals, as do all constitutional rights. They also protect society and help keep us free.
The rule's effectiveness in deterring illegal searches is hotly debated. The critics point out that some ninety percent of criminal prosecutions do not go to trial but are disposed of by pleas of "guilty." (The figure varies from state to state, and according to the nature of the crime.) Without a trial, there is no evidence for the rule to exclude. In the huge number of cases in which the police make arrests but the persons arrested are not prosecuted, the exclusionary rule has, of course, no immediate application. The rule's proponents reply that the decision whether to prosecute or accept a defendant's "guilty" pleas on a lesser offense may itself be influenced by the prosecutor's estimate of the potential operation of the exclusionary rule if the case should go to trial. (In jurisdictions where separate procedures are established to rule on motions to suppress evidence, the rule normally will have operated in advance of the trial.)
Undeniably, however, the exclusionary rule has no application at all to the cases that cry out most for a remedy: cases of police misconduct against innocent persons, who are never even brought to the prosecutors' attention, and cases of illegal searches and seizures made for purposes other than collecting evidence to support prosecutions. In terry v. ohio (1968) Chief Justice earl warren admitted: "Regardless how effective the rule may be where obtaining conviction is an important objective of the police, it is powerless to deter invasions of constitutionally guaranteed rights where the police either have no interest in prosecuting or are willing to forego successful prosecution in the interest of serving some other goal." The police may deliberately engage in illegal searches and seizures for a number of reasons: to control crimes such as gambling or prostitution; to confiscate weapons or contraband or stolen property; or to maintain high visibility either to deter crime or to satisfy a public clamoring for aggressive police action. In none of these cases will the exclusionary rule inhibit police violations of the Bill of Rights.
The rule does not in fact significantly impede the police, despite contentions from the rule's opponents that it handcuffs the police. A 1984 report prepared for the National Center for State Courts concluded that a properly administered search warrant process can protect constitutional rights without hampering effective law enforcement. Nevertheless, police try when possible to conduct search and seizure under some exception to the warrant requirement. The overwhelming number of searches and seizures are warrantless. In 1980, for example, only about 1,000 warrants were issued in Los Angeles in about 300,000 cases. Police usually try to make consent searches or searches under what they claim to be exigent circumstances, or they conduct a search to confiscate contraband or harass criminals, without attempting a prosecution. In the few cases in which they seek warrants, they get them almost as if magistrates rubber-stamp their applications, and almost all warrants survive in court despite motions to suppress. Motions to suppress are made in about five percent of all cases but are successful in only less than one percent of all cases. Still more important is the fact that only slightly over half of one percent of all cases result in acquittals because of the exclusion of evidence.
Even when the rule does operate to exclude evidence in a criminal trial, it has no direct, personal effect on the police officer whose misconduct caused the rule to be invoked. The rule does not require discipline to be imposed by the officer's superiors, nor does either civil or criminal responsibility follow as a matter of course. Police officers are prosecuted only extremely rarely for their official misdeeds. Suits for damages by victims are inhibited not only by the defense of "good faith" and probable cause but also by the realization that most officers are neither wealthy nor insured against liability for their official acts. Unsurprisingly, most victims conclude that a lawsuit is not worth its trouble and expense. In the typical case of an illegal search, neither the judge who excludes the fruits of the search from evidence nor the prosecutor whose case is thereby undermined will explain to the officer the error of his ways. The intended educational effect of judicial decisions is also diminished by the time-lag between the police action and its final evaluation by the courts. Even if an officer should hear that a court has excluded the evidence he found in an illegal search some months ago, he will probably have forgotten the details of the event. Incentives and sanctions that might influence the officer's future behavior are not within the exclusionary rule's contemplation. On the other hand, advocates of the rule emphasize that it is meant to have an institutional or systemic effect on law enforcement agencies generally, not necessarily on particular officers.
The officer is apt to respond not to judicial decisions (which he may regard as unrealistic if they impede his work) but to departmental policies and the approval of his colleagues and superiors. One whose main job is the apprehension of criminals and the deterrence of crime will have a low tolerance for what he sees as procedural niceties. He may even shade the truth in making out a report on a search or when testifying in court. It is not unheard of for the police to arrange to make a valid arrest at a place where they can conduct a warrantless search incident to the arrest, and thus evade the requirement of a search warrant based on probable cause to believe that evidence of crime is in that place. To the extent that the courts have used the exclusionary rule to educate the police, then, the main things learned seem to have been the techniques for evading the rule.
Summarizing the criticisms of the exclusionary rule, Dallin H. Oaks has said:
The harshest criticism of the rule is that it is ineffective. It is the sole means of enforcing the essential guarantees of freedom from unreasonable arrests and searches and seizures by law enforcement officers, and it is a failure in that vital task.
The use of the exclusionary rule imposes excessive costs on the criminal justice system. It provides no recompense for the innocent and it frees the guilty. It creates the occasion and incentive for large-scale lying by law enforcement officers. It diverts the focus on the criminal prosecution from the guilt or innocence of the defendant to a trial of the police. Only a system with limitless patience with irrationality could tolerate the fact that where there has been one wrong, the defendant's, he will be punished, but where there have been two wrongs, the defendant's and the officer's, both will go free. This would not be an excessive cost for an effective remedy against police misconduct, but it is a prohibitive price to pay for an illusory one.
Despite the severity of criticisms, the exclusionary rule's chief critics have not proposed its total abolition. However, the Supreme Court has limited the rule's application in significant ways. Thus, for the most part, only the victim of an illegal search has standing to claim the benefits of the exclusionary rule; if A's house is searched in violation of the Fourth Amendment, and evidence is found incriminating B, the evidence can be used in B's trial. (State courts are free to extend the exclusionary rule to such cases; some state courts have done so, concluding that the point of the rule is not to protect people against being convicted but to deter the police.) Similarly, in united states v. calandra (1974) the Court held that illegally obtained evidence is admissible in grand jury proceedings, and it ruled in harris v. new york (1971) that it can be used for the purpose of impeaching the testimony of the accused at his trial. Some uses of illegally obtained evidence have been tolerated as harmless error. More important, the good faith exception to the exclusionary rule allows the use of evidence obtained with a search warrant if the police reasonably believed the warrant to be valid, even though it later proves to be illegal. The rule has also been held inapplicable to collateral proceedings for postconviction relief such as habeas corpus. The Court's opinions in these cases have repeated the familiar criticisms of the exclusionary rule; their logic would seem to suggest abandonment of the rule altogether.
Yet the exclusionary rule remains, largely because no one has yet suggested an effective alternative means for enforcing the Bill of Rights against police misconduct. A federal statute dating from Reconstruction authorizes the award of damages against state or local officials (including police officers) who violate individuals' constitutional rights. In 1971, the Supreme Court found that the Fourth Amendment itself implicitly authorized similar damages awards against federal officers who violated the Amendment. The future effectiveness of such remedies will depend in part on the Supreme Court itself, as it spells out the victim's burden of proof in these cases and the measure of damages. Partly, however, the civil-damages alternative depends for its effectiveness on legislation to provide for real compensation to victims when the police officers are judgment-proof, and for real punishment of officers for constitutional violations when the payment of damages is unrealistic.
Meanwhile, the Supreme Court has only the exclusionary rule, which everyone agrees is an imperfect deterrent to police misbehavior. The rule survives, then, for want of better alternatives. But it also stands as a symbol that government itself is not above the law.
Leonard W. Levy
Oaks, Dallin H. 1970 Studying the Exclusionary Rule. University of Chicago Law Review 37:665–757.
Schroeder, William 1981 Deterring Fourth Amendment Violations: Alternatives to the Exclusionary Rule. Georgetown Law Review 68:1361–1426.
Stewart, Potter 1983 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 83:1365–1404.
The principle based on federalconstitutional lawthat evidence illegally seized by law enforcement officers in violation of a suspect's right to be free from unreasonablesearches and seizurescannot be used against the suspect in a criminal prosecution.
The exclusionary rule is designed to exclude evidence obtained in violation of a criminal defendant's fourth amendment rights. The Fourth Amendment protects against unreasonable searches and seizures by law enforcement personnel. If the search of a criminal suspect is unreasonable, the evidence obtained in the search will be excluded from trial.
The exclusionary rule is a court-made rule. This means that it was created not in statutes passed by legislative bodies but rather by the U.S. Supreme Court. The exclusionary rule applies in federal courts by virtue of the Fourth Amendment. The Court has ruled that it applies in state courts although the due process clause of the fourteenth amendment.(The Bill of Rights—the first ten amendments— applies to actions by the federal government. The Fourteenth Amendment, the Court has held, makes most of the protections in the bill of rights applicable to actions by the states.)
The exclusionary rule has been in existence since the early 1900s. Before the rule was fashioned, any evidence was admissible in a criminal trial if the judge found the evidence to be relevant. The manner in which the evidence had been seized was not an issue. This began to change in 1914, when the U.S. Supreme Court devised a way to enforce the Fourth Amendment. In Weeks v. United States, 232 U.S. 383, 34 S. Ct. 341, 58 L. Ed. 652 (1914), a federal agent had conducted a warrantless search for evidence of gambling at the home of Fremont Weeks. The evidence seized in the search was used at trial, and Weeks was convicted. On appeal, the Court held that the Fourth Amendment barred the use of evidence secured through a warrantless search. Weeks's conviction was reversed, and thus was born the exclusionary rule.
The exclusionary rule established in Weeks was constitutionally required only in federal court until mapp v. ohio, 367 U.S. 643, 81 S. Ct. 1684, 6 L. Ed. 2d 1081 (1961). In Mapp, Cleveland police officers had gone to the home of Dollree Mapp to ask her questions regarding a recent bombing. The officers demanded entrance into her home. Mapp called her attorney and then refused to allow the officers in without a warrant. The officers became rough with Mapp, handcuffed her, and searched her home. They found allegedly obscene books, pictures, and photographs.
Mapp was charged with violations of obscenity laws, prosecuted, convicted, and sentenced to seven years in prison. The Ohio Supreme Court affirmed the conviction, but the U.S. Supreme Court overturned it.
In Mapp, the Court held that the exclusionary rule applied to state criminal proceedings through the Due Process Clause of the Fourteenth Amendment. Before the Mapp ruling, not all states excluded evidence obtained in violation of the Fourth Amendment. Since Mapp, a defendant's claim of unreasonable search and seizure has become a matter of course in most criminal prosecutions.
A criminal defendant's claim of unreasonable search and seizure is usually heard in a suppression hearing before the presiding judge. This hearing is conducted before trial to determine what evidence will be suppressed, or excluded from trial.
The exclusionary rule is still regularly invoked by criminal defendants, but its golden age may have passed. Since the 1980s, the U.S. Supreme Court has severely limited its application. According to the Court, this rule was not devised to cure all Fourth Amendment violations. Rather, it was designed primarily to deter police misconduct. This construction led to the good faith exception to Fourth Amendment violations established in United States v. Leon, 468 U.S. 897, 104 S. Ct. 3405, 82 L. Ed. 2d 677 (1984).
In Leon, police officers searched the Burbank, California, home of Alberto A. Leon, and arrested Leon after they found a large quantity of drugs in his possession. The search was executed pursuant to a warrant that was later determined to be invalid. The information provided by the police in their affidavit in support of the warrant had been stale, which meant that too much time had passed between the observations that prompted it and the application for the warrant. No evidence suggested that a police officer had lied about facts. Rather, the staleness of the affidavit had simply been overlooked by the magistrate.
The drug evidence seized from Leon's home was excluded from trial by the U.S. District Court for the Central District of California, and the Ninth Circuit Court of Appeals affirmed the ruling. On appeal, the U.S. Supreme Court reversed, holding that evidence gathered in a search executed pursuant to a warrant later found to be defective should not be excluded from trial.
The majority in Leon opened its analysis by noting that the Fourth Amendment "contains no provisions expressly precluding the use of evidence obtained in violation of its commands." The exclusionary rule, according to the majority, was not designed to be a personal right. It was created by the Court "to deter police misconduct rather than to punish the errors of judges and magistrates." Under this interpretation, excluding evidence obtained through an honest mistake would serve no purpose. The Court's ruling in Leon meant that evidence obtained in violation of a person's Fourth Amendment rights would not be excluded from trial if the law enforcement officer, although mistaken, acted reasonably.
Justice john paul stevens dissented, arguing that the facts of the case did not warrant such a sweeping exception to the exclusionary rule. In a separate dissenting opinion, Justices william j. brennan, Jr and thurgood marshall conceded that, "as critics of the exclusionary rule never tire of repeating," the Fourth Amendment does not contain an express provision calling for the exclusion of evidence seized in violation of its commands. Brennan and Marshall dismissed this argument by noting that the Constitution is stated in general terms, and that the U.S. Supreme Court regularly creates doctrines designed to enforce its simple terms.
Brennan and Marshall maintained that "the chief deterrent function of the [exclusionary] rule is" far beyond the simple prevention of police misconduct, "the tendency to promote institutional compliance with Fourth Amendment requirements on the part of law enforcement agencies generally." In other words, if a search warrant is found defective at any point in the prosecution, the evidence should be excluded, even if the defect is due to an honest mistake. This, according to Brennan and Marshall, would preserve the integrity of both law enforcement and the Fourth Amendment. Brennan and Marshall concluded that the majority's reliance on the deterrence rationale "robbed the [exclusionary] rule of legitimacy."
In 1995, the U.S. Supreme Court revisited the good faith exception to the exclusionary rule. In Arizona v. Evans, 514 U.S. 1, 115 S. Ct. 1185, 131 L. Ed. 2d 34 (1995), the error of a court employee mistakenly listed Isaac Evans as the subject of a misdemeanor arrest warrant. A police officer had stopped Evans for a traffic violation, searched Evans pursuant to the faulty warrant information, and found marijuana.
On trial for possession of marijuana, Evans moved to suppress the marijuana evidence. The Maricopa County Superior Court granted the motion. The state of Arizona appealed, and the Arizona Court of Appeals reversed. The Supreme Court of Arizona then heard the case and held that the evidence should be excluded.
On appeal by the state of Arizona, the U.S. Supreme Court reversed, holding that evidence seized in violation of the Fourth Amendment as a result of clerical error need not be excluded from trial. In so holding, the Court emphasized that the Fourth Amendment exists only to guard against unreasonable police intrusions. According to the Court, "[The] use of the fruits of a past unlawful search or seizure 'works no new Fourth Amendment wrong'" (Evans, quoting Leon, quoting United States v. Calandra, 414 U.S. 338, 94 S. Ct. 613, 38 L. Ed. 2d 561 ).
The good faith exception established in Leon is just one exception that renders the exclusionary rule inoperable. Evidence seized by private parties is not excluded from trial if the search was not at the direction of law enforcement officers. If a criminal defendant testifies in her or his own defense, illegally seized evidence may be used to impeach the defendant's testimony. Evidence seized in violation of a person's Fourth Amendment rights may be used in grand jury proceedings and civil proceedings. In a grand jury proceeding, however, illegally seized evidence may not be used if it was obtained in violation of the federal wire tapping statute (18 U.S.C.A. § 2510 et seq.).
Few legal observers express complete satisfaction with the exclusionary rule. Some commentators criticize the U.S. Supreme Court for limiting the scope of the rule with the good faith exception. Others contend that the rule should be abolished because it impedes law enforcement. Some members of Congress have even proposed legislation to abolish the exclusionary rule in federal court. To date, no such legislation has been adopted.
The U.S. Supreme Court has continued to look at the application of the exclusionary rule to various types of searches and seizures. In Florida v. White, 526 U.S. 559, 119 S. Ct. 1555, 143 L. Ed. 2d 748 (1999), the Court gave police more discretion to search and seize without violating the Fourth Amendment's warrant requirement and thereby triggering the exclusionary rule. In that case, police did not need to obtain a warrant before seizing an automobile from a public place under laws that require forfeiture of property tied to crime. The Court rejected the argument that absent "exigent circumstances," police must obtain a warrant before seizing property that has been used in violation of the state forfeiture act. It pointed to its tradition of allowing police "greater latitude in exercising their duties in a public place." Although a warrant is generally required for a felony arrest in a suspect's home, the Fourth Amendment permits warrantless arrests in public places where police have probable cause to believe that a felony has occurred.
In a surprising departure from its Fourth Amendment jurisprudence, the U.S. Supreme Court ruled that an anonymous tip by itself does not give police officers the authority to stop and frisk a person for a weapon. Florida v. J.L., 529 U.S. 266, 120 S. Ct. 1375, 146 L. Ed. 2d 254 (2000). A police officer may stop and frisk a person for a firearm if the officer reasonably concludes that criminal activity may be contemplated and that the person may be armed and dangerous. However, if the search is based only on a anonymous tip, the seized weapon may not be offered into evidence, due to the exclusionary rule.
The U.S. Supreme Court also invoked the exclusionary rule in Kyllo v. United States, 533 U.S. 27, 121 S.Ct. 2038, 150 L.Ed.2d 94 (2001). It set out a new rule for police when they want to use new types of electronic surveillance, including thermal imaging, to examine the inner workings of a home. The Court held that police must apply for a warrant from a court before using a device that can obtain details of a private home that would have been unknowable without physical intrusion. If police fail to secure a warrant, the search will be regarded as "presumptively unreasonable" and the evidence that the search produced will be inadmissible at trial under the exclusionary rule.
The Court noted that the degree of privacy guaranteed by the Fourth Amendment had been affected by technological developments. The question became "what limits there are upon this power of technology to shrink the realm of guaranteed privacy?" Individuals had a "minimum expectation of privacy" that the interiors of their homes were not subject to warrantless police searches. Thus, the use of "sense-enhancing technology" that could obtain information that would otherwise only be obtainable by a physical search was a "search." This meant that any information obtained by the thermal imager was the product of a search, and a search was unreasonable and could only be justified if it was made pursuant to a warrant.
Calabresi, Guido. 2003. "The Exclusionary Rule." Harvard Journal of Law and Public Policy 26.
"Criminal Procedure." 1993. The Conviser Mini Review. Orlando, Fla.: Harcourt Brace Jovanovich Legal & Professional Publications.
Eiben, Valerie L. 1987. "The Good Faith Exception to the Exclusionary Rule: The New Federalism and a Texas Proposal." St. Mary's Law Journal 18.
Glasser, Larry. 2003. "The American Exclusionary Rule Debate." George Washington International Law Review 35.