CASES ADJUDGED

															IN THE

															SUPREME COURT OF THE UNITED STATES

															AT

															OCTOBER TERM, 1994

															Syllabus

															ARIZONA v. EVANS

															CERTIORARI TO THE SUPREME COURT OF ARIZONA No. 93-1660. Argued
December 7, 1994-Decided March 1, 1995

															Respondent was arrested by Phoenix police during a routine
traffic stop when a patrol car's computer indicated that there was
an outstanding misdemeanor warrant for his arrest. A subsequent
search of his car revealed a bag of marijuana, and he was charged
with possession. Respondent moved to suppress the marijuana as the
fruit of an unlawful arrest, since the misdemeanor warrant had been
quashed before his arrest. The trial court granted the motion, but
the Court of Appeals reversed on the ground that the exclusionary
rule's purpose would not be served by excluding evidence obtained
because of an error by employees not directly associated with the
arresting officers or their police department. In reversing, the
Arizona Supreme Court rejected the distinction between clerical
errors committed by law enforcement personnel and similar mistakes
by court employees and predicted that the exclusionary rule's
application would serve to improve the efficiency of criminal
justice system recordkeepers.

															Held:

															1. This Court has jurisdiction to review the State Supreme
Court's decision. Under Michigan v. Long, 463 U. S. 1032 , when a
state-court decision fairly appears to rest primarily on federal
law, or to be interwoven with federal law, and when the adequacy
and independence of any possible state-law ground is not clear from
the opinion's face, this Court will accept as the most reasonable
explanation that the state court decided the case the way it did
because it believed that federal law required it to do so. This
standard for determining whether a 2 Syllabus

															state-court decision rests upon an adequate and independent
state ground was adopted (1) to obviate the unsatisfactory and
intrusive practice of requiring state courts to clarify their
decisions to this Court's satisfaction and (2) to provide state
judges with a clearer opportunity to develop state jurisprudence
unimpeded by federal interference and yet preserve the federal
law's integrity. Michigan properly serves its purpose and
should not be disturbed. State courts are free both to interpret
state constitutional provisions to accord greater protection to
individual rights than do similar provisions of the United States
Constitution and to serve as experimental laboratories. However, in
cases where they interpret the United States Constitution, they are
not free from the final authority of this Court. In this case, the
State Supreme Court based its decision squarely upon its
interpretation of federal law when it discussed the appropriateness
of applying the exclusionary rule, and it offered no plain
statement that its references to federal law were being used only
for the purpose of guidance and did not compel the result reached.
Pp. 6-10.

															2. The exclusionary rule does not require suppression of
evidence seized in violation of the Fourth Amendment where the
erroneous information resulted from clerical errors of court
employees. The exclusionary rule is a judicially created remedy
designed to safeguard against future violations of Fourth Amendment
rights through its deterrent effect. However, the issue of
exclusion is separate from whether the Amendment has been violated.
The Amendment does not expressly preclude the use of evidence
obtained in violation of its commands, and exclusion is appropriate
only where the rule's remedial objectives are thought most
efficaciously served. The same framework that this Court used in United States v. Leon, 468 U. S. 897 , to
determine that there was no sound reason to apply the exclusionary
rule as a means of deterring misconduct on the part of judicial
officers responsible for issuing search warrants applies in this
case. The exclusionary rule was historically designed as a means of
deterring police misconduct, not mistakes by court employees. See id., at 916. In addition, respondent offers no evidence that
court employees are inclined to ignore or subvert the Fourth
Amendment or that lawlessness among these actors requires
application of the extreme sanction of exclusion. See ibid. In fact, the Justice Court Clerk testified that this type of error
occurred only once every three or four years. Finally, there is no
basis for believing that application of the exclusionary rule will
have a significant effect on court employees responsible for
informing the police that a warrant has been quashed. Since they
are not adjuncts to the law enforcement team engaged in ferreting
out crime, they have no stake in the outcome of particular
prosecutions. Application of the exclusionary rule also could
not 3 be expected to alter an arresting officer's behavior, since
there is no indication that the officer here was not acting
reasonably when he relied upon the computer record. pp. 10-16.

															177 Ariz. 201, 866 P. 2d 869, reversed and remanded.

															REHNQUIST, C. J., delivered the opinion of the Court, in which
O'CONNOR, SCALIA, KENNEDY, SOUTER, THOMAS, and BREYER, JJ., joined.
O'CONNOR, J., filed a concurring opinion, in which SOUTER and
BREYER, JJ., joined, post, p. 16. SOUTER, J., filed a
concurring opinion, in which BREYER, J., joined, post, p.
18. STEVENS, J., filed a dissenting opinion, post, p. 18.
GINSBURG, J., filed a dissenting opinion, in which STEVENS, J.,
joined, post, p. 23. Gerald R. Grant argued the cause and filed briefs for
petitioner. Carol A. Carrigan argued the cause and filed a brief for
respondent. *

															CHIEF JUSTICE REHNQUIST delivered the opinion of the Court.

															This case presents the question whether evidence seized in
violation of the Fourth Amendment by an officer who

															*Briefs of amici curiae urging reversal were filed for
the United States by Solicitor General Days, Assistant Attorney
General Harris, Deputy Solicitor General Bryson, and Jeffrey
P. Minear; for the State of Florida et al. by Robert A.
Butterworth, Attorney General of Florida, and Michael J. Neimand, Assistant Attorney General, and by the
Attorneys General for their respective jurisdictions as follows: James H. Evans of Alabama, Bruce M. Botelho of
Alaska, Larry EchoHawk of Idaho, Pamela Carter of
Indiana, Robert T. Stephan of Kansas, Chris Gorman of
Kentucky, Scott Harshbarger of Massachusetts, Joseph P.
Mazurek of Montana, Lee Fisher of Ohio, T. Travis
Medlock of South Carolina, Jeffrey L. Amestoy of
Vermont, and James S. Gilmore III of Virginia; for
Americans for Effective Law Enforcement, Inc., et al. by Richard
M. Weintraub, William C. O'Malley, Bernard J. Farber, Fred E. Inbau, Wayne W Schmidt, and James P.
Manak; and for the Washington Legal Foundation et al. by Paul Briefs of amici curiae urging affirmance were filed for
the American Civil Liberties Union et al. by Steven R.
Shapiro; and for the National Association of Criminal Defense
Lawyers by Ephraim Margolin and Barry P. Helft. 4 acted in reliance on a police record indicating the existence of
an outstanding arrest warrant-a record that is later determined to
be erroneous-must be suppressed by virtue of the exclusionary rule
regardless of the source of the error. The Supreme Court of Arizona
held that the exclusionary rule required suppression of evidence
even if the erroneous information resulted from an error committed
by an employee of the office of the Clerk of Court. We
disagree.

															In January 1991, Phoenix police officer Bryan Sargent observed
respondent Isaac Evans driving the wrong way on a one-way street in
front of the police station. The officer stopped respondent and
asked to see his driver's license. After respondent told him that
his license had been suspended, the officer entered respondent's
name into a computer data terminal located in his patrol car. The
computer inquiry confirmed that respondent's license had been
suspended and also indicated that there was an outstanding
misdemeanor warrant for his arrest. Based upon the outstanding
warrant, Officer Sargent placed respondent under arrest. While
being handcuffed, respondent dropped a hand-rolled cigarette that
the officers determined smelled of marijuana. Officers proceeded to
search his car and discovered a bag of marijuana under the
passenger's seat.

															The State charged respondent with possession of marijuana. When
the police notified the Justice Court that they had arrested him,
the Justice Court discovered that the arrest warrant previously had
been quashed and so advised the police. Respondent argued that
because his arrest was based on a warrant that had been quashed 17
days prior to his arrest, the marijuana seized incident to the
arrest should be suppressed as the fruit of an unlawful arrest.
Respondent also argued that "[t]he 'good faith' exception to the
exclusionary rule [was] inapplicable ... because it was police
error, not judicial error, which caused the invalid arrest." App.
5.

															At the suppression hearing, the Chief Clerk of the Justice Court
testified that a Justice of the Peace had issued the 5 arrest warrant on December 13, 1990, because respondent had
failed to appear to answer for several traffic violations. On
December 19, 1990, respondent appeared before a pro tem Justice of the Peace who entered a notation in respondent's file to
"quash warrant." Id., at 13.

															The Chief Clerk also testified regarding the standard court
procedure for quashing a warrant. Under that procedure a justice
court clerk calls and informs the warrant section of the Sheriff's
Office when a warrant has been quashed. The Sheriff's Office then
removes the warrant from its computer records. After calling the
Sheriff's Office, the clerk makes a note in the individual's file
indicating the clerk who made the phone call and the person at the
Sheriff's Office to whom the clerk spoke. The Chief Clerk testified
that there was no indication in respondent's file that a clerk had
called and notified the Sheriff's Office that his arrest warrant
had been quashed. A records clerk from the Sheriff's Office also
testified that the Sheriff's Office had no record of a telephone
call informing it that respondent's arrest warrant had been
quashed. Id., at 42-43.

															At the close of testimony, respondent argued that the evidence
obtained as a result of the arrest should be suppressed because
"the purposes of the exclusionary rule would be served here by
making the clerks for the court, or the clerk for the Sheriff's
office, whoever is responsible for this mistake, to be more careful
about making sure that warrants are removed from the records." Id., at 47. The trial court granted the motion to suppress
because it concluded that the State had been at fault for failing
to quash the warrant. Presumably because it could find no
"distinction between State action, whether it happens to be the
police department or not," id., at 52, the trial court made
no factual finding as to whether the Justice Court or Sheriff's
Office was responsible for the continued presence of the quashed
warrant in the police records. 6 A divided panel of the Arizona Court of Appeals reversed because
it "believe[d] that the exclusionary rule [was] not intended to
deter justice court employees or Sheriff's Office employees who are
not directly associated with the arresting officers or the
arresting officers' police department." 172 Ariz. 314, 317, 836 P.
2d 1024, 1027 (1992). Therefore, it concluded, "the purpose of the
exclusionary rule would not be served by excluding the evidence
obtained in this case." Ibid. The Arizona Supreme Court reversed. 177 Ariz. 201, 866 P. 2d 869
(1994). The court rejected the "distinction drawn by the court of
appeals ... between clerical errors committed by law enforcement
personnel and similar mistakes by court employees." Id., at
203, 866 P. 2d, at 871. The court predicted that application of the
exclusionary rule would "hopefully serve to improve the efficiency
of those who keep records in our criminal justice system." Id., at 204, 866 P. 2d, at 872. Finally, the court concluded
that "[e]ven assuming that deterrence is the principal reason for
application of the exclusionary rule, we disagree with the court of
appeals that such a purpose would not be served where carelessness
by a court clerk results in an unlawful arrest." Ibid. We granted certiorari to determine whether the exclusionary rule
requires suppression of evidence seized incident to an arrest
resulting from an inaccurate computer record, regardless of whether
police personnel or court personnel were responsible for the
record's continued presence in the police computer. 511 U. S. 1126
(1994).1 We now reverse.

															We first must consider whether we have jurisdiction to review
the Arizona Supreme Court's decision. Respondent argues that we
lack jurisdiction under 28 U. S. C. § 1257 because the Arizona
Supreme Court never passed upon the

															1 Petitioner has conceded that respondent's arrest violated the
Fourth Amendment. Brieffor Petitioner 10. We decline to review that
determination. Cf. United States v. Leon, 468 U. S. 897 , 905
(1984); Illinois v. Krull, 480 U. S. 340 , 357, n. 13
(1987). 7 Fourth Amendment issue and instead based its decision on the
Arizona good-faith statute, Ariz. Rev. Stat. Ann. § 133925 (1993),
an adequate and independent state ground. In the alternative,
respondent asks that we remand to the Arizona Supreme Court for
clarification.

															In Michigan v. Long, 463 U. S. 1032 (1983),
we adopted a standard for determining whether a state-court
decision rested upon an adequate and independent state ground. When
"a state court decision fairly appears to rest primarily on federal
law, or to be interwoven with the federal law, and when the
adequacy and independence of any possible state law ground is not
clear from the face of the opinion, we will accept as the most
reasonable explanation that the state court decided the case the
way it did because it believed that federal law required it to do
so." Id., at 1040-1041. We adopted this practice, in part,
to obviate the "unsatisfactory and intrusive practice of requiring
state courts to clarify their decisions to the satisfaction of this
Court." Id., at 1041. We also concluded that this approach
would "provide state judges with a clearer opportunity to develop
state jurisprudence unimpeded by federal interference, and yet will
preserve the integrity of federal law." Ibid. JUSTICE GINSBURG would overrule Michigan v. Long, supra, because she believes that the rule of that case "impedes the
States' ability to serve as laboratories for testing solutions to
novel legal problems." Post, at 24.2 The opin-

															2 JUSTICE GINSBURG certainly is correct when she notes that"
'[s]ince Long, we repeatedly have followed [its] "plain
statement" requirement.'" Post, at 33 (quoting Harris v. Reed, 489
U. S. 255 , 261, n. 7 (1989) (opinion of Blackmun, J.)); see
also Illinois v. Rodriguez, 497 U. S. 177 , 182 (1990)
(opinion of SCALIA, J.); Pennsylvania v. Muniz, 496 U. S. 582 ,
588, n. 4 (1990) (opinion of Brennan, J.); Maryland v. Garrison, 480
U. S. 79 ,83-84 (1987) (opinion of STEVENS, J.); Caldwell v. Mississippi, 472 U. S. 320 ,327328
(1985) (opinion of Marshall, J.); California v. Carney, 471 U.
S. 386 , 389, n. 1 (1985) (opinion of Burger, C. J.); Ohio v. Johnson, 467 U. S. 493 , 497-498,
n. 7 (1984) (opinion of REHNQUIST, J.); Oliver v. United
States, 466 U. S.
170 , 175-176, n. 5 (1984) (opinion of Powell, J.); cf. Coleman 8 ion in Long describes the 60-year history of the Court's
differing approaches to the determination whether the judgment of
the highest court of a State rested on federal or nonfederal
grounds. 463 U. S., at 1038-1040. When we were in doubt, on some
occasions we dismissed the writ of certiorari; on other occasions
we vacated the judgment of the state court and remanded so that it
might clarify the basis for its decision. See ibid. The
latter approach did not always achieve the desired result and
burdened the state courts with additional work. Ibid. We believe that Michigan v. Long properly serves
its purpose and should not be disturbed. Under it, state courts are
absolutely free to interpret state constitutional provisions to
accord greater protection to individual rights than do similar
provisions of the United States Constitution. They also are free to
serve as experimental laboratories, in the sense that Justice
Brandeis used that term in his dissenting opinion in New State
Ice Co. v. Liebmann, 285 U. S. 262 , 311 (1932)
(urging that the Court not impose federal constitutional restraints
on the efforts of a State to "serve as a laboratory"). Under our
decision today, the State of Arizona remains free to seek whatever
solutions it chooses to problems of law enforcement posed by the
advent of computerization.3 Indeed, it is freer to do so because it
is disabused of its erroneous view of what the United States
Constitution requires.

															State courts, in appropriate cases, are not merely free tothey
are bound to-interpret the United States Constitution. In doing so,
they are not free from the final authority of this

															v. Thompson, 501 U. S. 722 , 740 (1991)
(opinion of O'CONNOR, J.) (declining to expand the Long and Harris presumption to instances "where the relevant state
court decision does not fairly appear to rest primarily on federal
law or to be interwoven with such law").

															3 JUSTICE GINSBURG acknowledges as much when she states that
since Long, "state courts, on remand, have reinstated their
prior judgments after clarifying their reliance on state grounds." Post, at 32 (citing statistics). 9 Court. This principle was enunciated in Cohens v. Virginia, 6 Wheat. 264 (1821), and presumably JUSTICE
GINSBURG does not quarrel with it.4 In Minnesota v. National Tea Co., 309 U. S. 551 (1940), we
recognized that our authority as final arbiter of the United States
Constitution could be eroded by a lack of clarity in state-court
decisions. "It is fundamental that state courts be left free and unfettered
by us in interpreting their state constitutions. But it is equally
important that ambiguous or obscure adjudications by state courts
do not stand as barriers to a determination by this Court of the
validity under the federal constitution of state action.
Intelligent exercise of our appellate powers compels us to ask for
the elimination of the obscurities and ambiguities from the
opinions in such cases .... For no other course assures that
important federal issues, such as have been argued here, will reach
this Court for adjudication; that state courts will not be the
final arbiters of important issues under the federal constitution;
and that we will not encroach on the constitutional jurisdiction of
the states." Id., at 557. We therefore adhere to the standard adopted in Michigan v. Long, supra. Applying that standard here, we conclude that we have
jurisdiction. In reversing the Court of Appeals, the Arizona
Supreme Court stated that "[w]hile it may be inappropriate to
invoke the exclusionary rule where a magistrate has issued a
facially valid warrant (a discretionary judicial function) based on
an erroneous evaluation of the facts, the law, or both, Leon, 468 U.
S. 897 ... (1984), it is useful and proper

															4 Surely if we have jurisdiction to vacate and remand a
state-court judgment for clarification, post, at 34, n. 7,
we also must have jurisdiction to determine whether a state-court
judgment is based upon an adequate and independent state ground.
See Abie State Bank v. Bryan, 282 U. S. 765 , 773
(1931). 10 to do so where negligent record keeping (a purely clerical
function) results in an unlawful arrest." 177 Ariz., at 204, 866 P.
2d, at 872. Thus, the Arizona Supreme Court's decision to suppress
the evidence was based squarely upon its interpretation of federal
law. See ibid. Nor did it offer a plain statement that its
references to federal law were "being used only for the purpose of
guidance, and d[id] not themselves compel the result that [it]
reached." Long, supra, at 1041.

															The Fourth Amendment states that "[t]he right of the people to
be secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be violated, and no
Warrants shall issue, but upon probable cause, supported by Oath or
affirmation, and particularly describing the place to be searched,
and the persons or things to be seized." We have recognized,
however, that the Fourth Amendment contains no provision expressly
precluding the use of evidence obtained in violation of its
commands. See United States v. Leon, 468 U. S. 897 , 906
(1984). "The wrong condemned by the [Fourth] Amendment is 'fully
accomplished' by the unlawful search or seizure itself," ibid. (quoting United States v. Calandra, 414 U. S. 338 ,
354 (1974)), and the use of the fruits of a past unlawful search or
seizure "'work[s] no new Fourth Amendment wrong,'" Leon,
supra, at 906 (quoting Calandra, supra, at 354).

															"The question whether the exclusionary rule's remedy is
appropriate in a particular context has long been regarded as an
issue separate from the question whether the Fourth Amendment
rights of the party seeking to invoke the rule were violated by
police conduct." Illinois v. Gates, 462 U. S. 213 , 223
(1983); see also United States v. Havens, 446 U. S. 620 , 627-628
(1980); Stone v. Powell, 428 U. S. 465 , 486-487 (1976); Calandra, supra, at 348. The exclusionary rule
operates as a judicially created remedy designed to safeguard
against future violations of Fourth Amendment rights through the
rule's general deterrent effect. Leon, supra, at 11 906; Calandra, supra, at 348. As with any remedial
device, the rule's application has been restricted to those
instances where its remedial objectives are thought most
efficaciously served. Leon, supra, at 908; Calandra,
supra, at 348. Where "the exclusionary rule does not result in
appreciable deterrence, then, clearly, its use ... is unwarranted." United States v. Janis, 428 U. S. 433 , 454
(1976).

															In Leon, we applied these principles to the context of a
police search in which the officers had acted in objectively
reasonable reliance on a search warrant, issued by a neutral and
detached Magistrate, that later was determined to be invalid. 468
U. S., at 905. On the basis of three factors, we determined that
there was no sound reason to apply the exclusionary rule as a means
of deterring misconduct on the part of judicial officers who are
responsible for issuing warrants. See Illinois v. Krull, 480 U.
S. 340 , 348 (1987) (analyzing Leon, supra). First, we
noted that the exclusionary rule was historically designed "'to
deter police misconduct rather than to punish the errors of judges
and magistrates.' " Krull, supra, at 348 (quoting Leon,
supra, at 916). Second, there was "'no evidence suggesting that
judges and magistrates are inclined to ignore or subvert the Fourth
Amendment or that lawlessness among these actors requires the
application of the extreme sanction of exclusion.''' Krull,
supra, at 348 (quoting Leon, supra, at 916). Third, and
of greatest importance, there was no basis for believing that
exclusion of evidence seized pursuant to a warrant would have a
significant deterrent effect on the issuing judge or magistrate. Krull, supra, at 348.

															The Leon Court then examined whether application of the
exclusionary rule could be expected to alter the behavior of the
law enforcement officers. We concluded: "[W]here the officer's conduct is objectively reasonable,
'excluding the evidence will not further the ends of the
exclusionary rule in any appreciable way; for it is painfully
apparent that ... the officer is acting as a reason- 12 able officer would and should act in similar circumstances.
Excluding the evidence can in no way affect his future conduct
unless it is to make him less willing to do his duty.'" Leon,
supra, at 919-920 (quoting Stone, supra, at 539-540
(White, J., dissenting)). See also Massachusetts v. Sheppard, 468 U. S. 981 , 990-991
(1984) ("[S]uppressing evidence because the judge failed to make
all the necessary clerical corrections despite his assurances that
such changes would be made will not serve the deterrent function
that the exclusionary rule was designed to achieve"). Thus, we held
that the "marginal or nonexistent benefits produced by suppressing
evidence obtained in objectively reasonable reliance on a
subsequently invalidated search warrant cannot justify the
substantial costs of exclusion." Leon, supra, at 922.

															Respondent relies on United States v. Hensley, 469 U. S. 221 (1985), and argues that the evidence seized incident to his arrest
should be suppressed because he was the victim of a Fourth
Amendment violation. Brief for Respondent 10-12, 21-22. In Hensley, the Court determined that evidence uncovered as a
result of a stop pursuant to Terry v. Ohio, 392 U. S. 1 (1968), was
admissible because the officers who made the stop acted in
objectively reasonable reliance on a flyer that had been issued by
officers of another police department who possessed a reasonable
suspicion to justify a Terry stop. 469 U. S., at 231.
Because the Hensley Court determined that there had been no
Fourth Amendment violation, id., at 236, the Court never
considered whether the seized evidence should have been excluded. Hensley does not contradict our earlier pronouncements that
"[t]he question whether the exclusionary rule's remedy is
appropriate in a particular context has long been regarded as an
issue separate from the question whether the Fourth Amendment
rights of the party seeking to invoke the rule were violated by
police conduct." Gates, supra, at 223; see also Stone,
supra, at 486-487; Calandra, supra, at 348. 13 Respondent also argues that Whiteley v. Warden,
Wyo. State Penitentiary, 401 U. S. 560 (1971),
compels exclusion of the evidence. In Whiteley, the Court
determined that the Fourth Amendment had been violated when police
officers arrested Whiteley and recovered inculpatory evidence based
upon a radio report that two suspects had been involved in two
robberies. Id., at 568-569. Although the "police were
entitled to act on the strength of the radio bulletin," the Court
determined that there had been a Fourth Amendment violation because
the initial complaint, upon which the arrest warrant and subsequent
radio bulletin were based, was insufficient to support an
independent judicial assessment of probable cause. Id., at
568. The Court concluded that "an otherwise illegal arrest cannot
be insulated from challenge by the decision of the instigating
officer to rely on fellow officers to make the arrest." Ibid. Because the "arrest violated [Whiteley's]
constitutional rights under the Fourth and Fourteenth Amendments;
the evidence secured as an incident thereto should have been
excluded from his trial. Mapp v. Ohio, 367 U. S. 643 (1961)." Id., at 568-569.

															Although Whiteley clearly retains relevance in
determining whether police officers have violated the Fourth
Amendment, see Hensley, supra, at 230-231, its precedential
value regarding application of the exclusionary rule is dubious. In Whiteley, the Court treated identification of a Fourth
Amendment violation as synonymous with application of the
exclusionary rule to evidence secured incident to that violation.
401 U. S., at 568-569. Subsequent case law has rejected this
reflexive application of the exclusionary rule. Cf. Illinois v. Krull, 480
U. S. 340 (1987); Sheppard, supra; United States v. Leon, 468 U.
S. 897 (1984); United States v. Calandra, 414 U. S. 338 (1974). These later cases have emphasized that the issue of
exclusion is separate from whether the Fourth Amendment has been
violated, see, e. g., Leon, supra, at 906, and
exclusion is appropriate only if the 14 remedial objectives of the rule are thought most efficaciously
served, see Calandra, supra, at 348.

															Our approach is consistent with the dissenting Justices'
position in Krull, our only major case since Leon and Sheppard involving the good-faith exception to the
exclusionary rule. In that case, the Court found that the
good-faith exception applies when an officer conducts a search in
objectively reasonable reliance on the constitutionality of a
statute that subsequently is declared unconstitutional. Krull,
supra, at 346. Even the dissenting Justices in Krull agreed that Leon provided the proper framework for analyzing
whether the exclusionary rule applied; they simply thought that
"application of Leon's stated rationales le[d] to a contrary
result." 480 U. S., at 362 (O'CONNOR, J., dissenting). In sum,
respondent does not persuade us to abandon the Leon framework.

															Applying the reasoning of Leon to the facts of this case,
we conclude that the decision of the Arizona Supreme Court must be
reversed. The Arizona Supreme Court determined that it could not
"support the distinction drawn ... between clerical errors
committed by law enforcement personnel and similar mistakes by
court employees," 177 Ariz., at 203, 866 P. 2d, at 871, and that
"even assuming ... that responsibility for the error rested with
the justice court, it does not follow that the exclusionary rule
should be inapplicable to these facts," ibid. This holding is contrary to the reasoning of Leon, supra;
Massachusetts v. Sheppard, supra; and, Krull,
supra. If court employees were responsible for the erroneous
computer record, the exclusion of evidence at trial would not
sufficiently deter future errors so as to warrant such a severe
sanction. First, as we noted in Leon, the exclusionary rule
was historically designed as a means of deterring police
misconduct, not mistakes by court employees. See Leon,
supra, at 916; see also Krull, supra, at 350. Second,
respondent offers no evidence that court employees are in- 15 clined to ignore or subvert the Fourth Amendment or that
lawlessness among these actors requires application of the extreme
sanction of exclusion. See Leon, supra, at 916, and n. 14;
see also Krull, supra, at 350-351. To the contrary, the
Chief Clerk of the Justice Court testified at the suppression
hearing that this type of error occurred once every three or four
years. App. 37.

															Finally, and most important, there is no basis for believing
that application of the exclusionary rule in these circumstances
will have a significant effect on court employees responsible for
informing the police that a warrant has been quashed. Because court
clerks are not adjuncts to the law enforcement team engaged in the
often competitive enterprise of ferreting out crime, see Johnson v. United States, 333 U. S. 10 , 14 (1948),
they have no stake in the outcome of particular criminal
prosecutions. Cf. Leon, supra, at 917; Krull, supra, at 352. The threat of exclusion of evidence could not be expected
to deter such individuals from failing to inform police officials
that a warrant had been quashed. Cf. Leon, supra, at 917; Krull, supra, at 352.

															If it were indeed a court clerk who was responsible for the
erroneous entry on the police computer, application of the
exclusionary rule also could not be expected to alter the behavior
of the arresting officer. As the trial court in this case stated:
"I think the police officer [was] bound to arrest. I think he would
[have been] derelict in his duty if he failed to arrest." App. 51.
Cf. Leon, supra, at 920 (" 'Excluding the evidence can in no
way affect [the officer's] future conduct unless it is to make him
less willing to do his duty.' " quoting Stone, 428 U. S., at
540 (White, J., dissenting)). The Chief Clerk of the Justice Court
testified that this type of error occurred "on[c]e every three or
four years." App. 37. In fact, once the court clerks discovered the
error, they immediately corrected it, id., at 30, and then
proceeded to search their files to make sure that no similar
mistakes had occurred, id., at 37. There is no indication
that the arresting 16 officer was not acting objectively reasonably when he relied
upon the police computer record. Application of the Leon framework supports a categorical exception to the exclusionary rule
for clerical errors of court employees. See Leon, supra, at
916-922; Sheppard, supra, at 990-991.5

															The judgment of the Supreme Court of Arizona is therefore
reversed, and the case is remanded to that court for proceedings
not inconsistent with this opinion.

															It is so ordered.

															JUSTICE O'CONNOR, with whom JUSTICE SOUTER and JUSTICE BREYER
join, concurring.

															The evidence in this case strongly suggests that it was a court
employee's departure from established recordkeeping procedures that
caused the record of respondent's arrest warrant to remain in the
computer system after the warrant had been quashed. Prudently,
then, the Court limits itself to the question whether a court
employee's departure from such established procedures is the kind
of error to which the exclusionary rule should apply. The Court
holds that it is not such an error, and I agree with that
conclusion and join the Court's opinion. The Court's holding
reaffirms that the exclusionary rule imposes significant costs on
society's law enforcement interests and thus should apply only
where its deterrence purposes are "most efficaciously served," ante, at 11.

															In limiting itself to that single question, however, the Court
does not hold that the court employee's mistake in this case was
necessarily the only error that may have occurred and to
which the exclusionary rule might apply. While the

															5 The Solicitor General, as amicus curiae, argues that an
analysis similar to that we apply here to court personnel also
would apply in order to determine whether the evidence should be
suppressed if police personnel were responsible for the error. As
the State has not made any such argument here, we agree that "[t]he
record in this case ... does not adequately present that issue for
the Court's consideration." Brief for United States as Amicus
Curiae 13. Accordingly, we decline to address that
question. 17 police were innocent of the court employee's mistake, they mayor
may not have acted reasonably in their reliance on the
recordkeeping system itself Surely it would not be
reasonable for the police to rely, say, on a recordkeeping system,
their own or some other agency's, that has no mechanism to ensure
its accuracy over time and that routinely leads to false arrests,
even years after the probable cause for any such arrest has ceased
to exist (if it ever existed).

															This is saying nothing new. We have said the same with respect
to other information sources police use, informants being an
obvious example. In Illinois v. Gates, 462 U. S. 213 (1983), the
Court indicated that where an informant provides information about
certain criminal activities but does not specify the basis for his
knowledge, a finding of probable cause based on that information
will not be upheld unless the informant is "known for [his] unusual
reliability." Id., at 233, citing United States v. Sellers, 483 F.2d
37 , 40, n. 1 (CA5 1973) (involving informant who had provided
accurate information "in more than one hundred instances in matters
of investigation"); see generally 1 W. LaFave, Search and Seizure §
3.3(b) (2d ed. 1987 and Supp. 1995). Certainly the reliability of
recordkeeping systems deserves no less scrutiny than that of
informants. Of course, the comparison to informants may be
instructive the opposite way as well. So long as an informant's
reliability does pass constitutional muster, a finding of probable
cause may not be defeated by an after-the-fact showing that the
information the informant provided was mistaken. See 2 id., § 3.5(d), at 21, n. 73 (citation omitted); see also 1 id., §
3.2(d), at 575 ("It is axiomatic that hindsight may not be employed
in determining whether a prior arrest or search was made upon
probable cause").

															In recent years, we have witnessed the advent of powerful,
computer-based recordkeeping systems that facilitate arrests in
ways that have never before been possible. The police, of course,
are entitled to enjoy the substantial advantages this technology
confers. They may not, however, rely on it blindly. With the
benefits of more efficient law enforce- 18 ment mechanisms comes the burden of corresponding constitutional
responsibilities.

															JUSTICE SOUTER, with whom JUSTICE BREYER joins, concurring.

															In joining the Court's opinion, I share JUSTICE O'CONNOR'S
understanding of the narrow scope of what we hold today. To her
concurrence, which I join as well, I add only that we do not answer
another question that may reach us in due course, that is, how far,
in dealing with fruits of computerized error, our very concept of
deterrence by exclusion of evidence should extend to the government
as a whole, not merely the police, on the ground that there would
otherwise be no reasonable expectation of keeping the number of
resulting false arrests within an acceptable minimum limit.

															JUSTICE STEVENS, dissenting.

															JUSTICE GINSBURG has written an important opinion explaining why
the Court unwisely departed from settled law when it interpreted
its own jurisdiction so expansively in Michigan v. Long, 463 U.
S. 1032 (1983). I join her dissent and her conclusion that the
writ of certiorari should be dismissed. Because the Court has
addressed the merits, however, I add this comment on its
holding.

															The Court seems to assume that the Fourth Amendmentand
particularly the exclusionary rule, which effectuates the
Amendment's commands-has the limited purpose of deterring police
misconduct. Both the constitutional text and the history of its
adoption and interpretation identify a more majestic conception.
The Amendment protects the fundamental "right of the people to be
secure in their persons, houses, papers, and effects," against all official searches and seizures that are unreasonable.
The Amendment is a constraint on the power of the sovereign, not
merely on some of its agents. See Olmstead v. United
States, 277 U. S.
438 , 472-479 (1928) (Brandeis, J., dissenting). The remedy for
its violation imposes costs on that sovereign, motivating it to
train all of 19 its personnel to avoid future violations. See Stewart, The Road
to Mapp v. Ohio and Beyond: The Origins, Development and
Future of the Exclusionary Rule in Search-andSeizure Cases, 83
Colum. L. Rev. 1365, 1400 (1983).

															The exclusionary rule is not fairly characterized as an "extreme
sanction," ante, at 11 (internal quotation marks omitted).
As Justice Stewart cogently explained, the implementation of this
constitutionally mandated sanction merely places the government in
the same position as if it had not conducted the illegal search and
seizure in the first place. 1 Given the undisputed fact in this
case that the Constitution prohibited the warrantless arrest of
respondent, there is nothing "extreme" about the Arizona Supreme
Court's conclusion that the State should not be permitted to profit
from its negligent misconduct.

															Even if one accepts deterrence as the sole rationale for the
exclusionary rule, the Arizona Supreme Court's decision is correct
on the merits. The majority's reliance on United States v. Leon, 468 U.
S. 897 (1984), is misplaced. The search in that case had been
authorized by a presumptively valid warrant issued by a California
Superior Court Judge. In

															1 See Stewart, The Road to Mapp v. Ohio and Beyond: The
Origins, Development and Future of the Exclusionary Rule in
Search-and-Seizure Cases, 83 Colum. L. Rev. 1365, 1392 (1983). I am
fully aware of the Court's statements that the question whether the
exclusionary rule should be applied is distinct from the question
whether the Fourth Amendment has been violated. Indeed, the
majority twice quotes the same statement from the Court's opinion
in Illinois v. Gates, 462 U. S. 213 , 223
(1983). See ante, at 10, 12. I would note that such eminent
Members of this Court as Justices Holmes, Brandeis, Harlan, and
Stewart have expressed the opposite view. See, e. g.,
Olmstead v. United States, 277 U. S. 438 ,470 (1928)
(Holmes, J., dissenting); id., at 477-479 (Brandeis, J.,
dissenting); Whiteley v. Warden, Wyo. State
Penitentiary, 401
U. S. 560 (1971) (Harlan, J.); Elkins v. United
States, 364 U. S.
206 (1960) (Stewart, J.); Stewart, supra, at 1383-1385.
The majority today candidly acknowledges that Justice Harlan's
opinion for the Court in Whiteley "treated identification of
a Fourth Amendment violation as synonymous with application of the
exclusionary rule to evidence secured incident to that violation." Ante, at 13. 20 contrast, this case involves a search pursuant to an arrest made
when no warrant at all was outstanding against respondent. The
holding in Leon rested on the majority's doubt "that
exclusion of evidence seized pursuant to a warrant will have a
significant deterrent effect on the issuing judge or magistrate." Id., at 916. The reasoning in Leon assumed the
existence of a warrant; it was, and remains, wholly inapplicable to
warrantless searches and seizures.2

															The Fourth Amendment's Warrant Clause provides the fundamental
check on official invasions of the individual's right to privacy. E. g., Harris v. United States, 331 U. S. 145 ,
195-196 (1947) (Jackson, J., dissenting); see generally Kamisar,
Does (Did) (Should) the Exclusionary Rule Rest on a "Principled
Basis" Rather Than an "Empirical Proposition"?, 16 Creighton L.
Rev. 565, 571-579 (1983). Leon stands for the dubious but
limited proposition that courts should not look behind the face of
a warrant on which police have relied in good faith. The Leon Court's exemption of judges and magistrates from the
deterrent ambit of the exclusionary rule rested, consistently with
the emphasis on the warrant requirement, on those officials'
constitutionally determined role in issuing warrants. See 468 U.
S., at 915917. Taken on its own terms, Leon's logic does not
extend to the time after the warrant has issued; nor does it extend
to court clerks and functionaries, some of whom work in the same
building with police officers and may have more regular and direct
contact with police than with judges or magistrates.

															2 As JUSTICE O'CONNOR observed in her dissent in Illinois v. Krull, 480 U. S. 340 (1987): "[T]he Leon Court
relied explicitly on the tradition of judicial independence in
concluding that, until it was presented with evidence to the
contrary, there was relatively little cause for concern that
judicial officers might take the opportunity presented by the
good-faith exception to authorize unconstitutional searches." Id., at 365. I joined that dissent, and I take exception to
the majority's pronouncement that today's opinion is "consistent
with" it. Ante, at 14. 21 The Phoenix Police Department was part of the chain of
information that resulted in respondent's unlawful, warrantless
arrest. We should reasonably presume that law enforcement
officials, who stand in the best position to monitor such errors as
occurred here, can influence mundane communication procedures in
order to prevent those errors. That presumption comports with the
notion that the exclusionary rule exists to deter future police
misconduct systemically. See, e. g., Stone v. Powell, 428 U.
S. 465 , 492 (1976); Dunaway v. New York, 442 U. S. 200 , 221 (1979)
(STEVENS, J., concurring); see generally Kamisar, 16 Creighton L.
Rev., at 659662; Stewart, 83 Colum. L. Rev., at 1400. The deterrent
purpose extends to law enforcement as a whole, not merely to "the
arresting officer." Compare ante, at 15, with Whiteley v. Warden, Wyo. State Penitentiary, 401 U. S. 560 , 568
(1971). Consequently, the Phoenix officers' good faith does not
diminish the deterrent value of invalidating their arrest of
respondent.

															The Court seeks to minimize the impact of its holding on the
security of the citizen by referring to the testimony of the Chief
Clerk of the East Phoenix Number One Justice Court that in her
"particular court" this type of error occurred "'maybe on[c]e every
three or four years.'" See ante, at 15. Apart from the fact
that the Clerk promptly contradicted herself,3 see post, at
28, this is slim evidence

															3 "Q. In your eight years as a chief clerk with the Justice of
the Peace, have there been other occasions where a warrant was
quashed but the police were not notified?

															"A. That does happen on rare occasions.

															"Q. And when you say rare occasions, about how many times in
your eight years as chief clerk?

															"A. In my particular court, they would be like maybe one every
three or four years.

															"Q. When something like this happens, is anything done by your
office to correct that problem?

															"A. Well, when this one happened, we searched all the files to
make sure that there were no other ones in there, which there were
three other ones 22 on which to base a conclusion that computer error poses no
appreciable threat to Fourth Amendment interests. For support, the
Court cites a case from 1948. See ante, at 15, citing Johnson v. United States, 333 U. S. 10 . The Court
overlooks the reality that computer technology has changed the
nature of threats to citizens' privacy over the past half century.
See post, at 26-28. What has not changed is the reality that
only that fraction of Fourth Amendment violations held to have
resulted in unlawful arrests is ever noted and redressed. As
Justice Jackson observed: "There may be, and I am convinced that
there are, many unlawful searches ... of innocent people which turn
up nothing incriminating, in which no arrest is made, about which
courts do nothing, and about which we never hear." Brinegar v. United States, 338 U. S. 160 , 181 (1949)
(dissenting opinion). Moreover, even if errors in computer records
of warrants were rare, that would merely minimize the cost of
enforcing the exclusionary rule in cases like this.

															While I agree with JUSTICE GINSBURG that premature adjudication
of this issue is particularly unwise because we have much to learn
about the consequences of computer error as well as the efficacy of
other preventive measures, see post, at 29-30, one
consequence of the Court's holding seems immediately obvious. Its
most serious impact will be on the otherwise innocent citizen who
is stopped for a minor traffic infraction and is wrongfully
arrested based on erroneous information in a computer data base. I
assume the police officer who reasonably relies on the computer
information would be immune from liability in a § 1983 action. Of
course, the Court has held that respondeat superior is
unavailable as a basis for imposing liability on his or her
municipality. See Monell v. New York City Dept. of Social
Servs., 436 U. S.
658 , 663-664, n. 7 (1978). Thus, if courts are to

															on that same day that it happened. Fortunately, they weren't all
arrested." App.37. 23 have any power to discourage official error of this kind, it
must be through application of the exclusionary rule.

															The use of general warrants to search for evidence of violations
of the Crown's revenue laws understandably outraged the authors of
the Bill of Rights. See, e. g., Lo-Ji Sales,
Inc. v. New York, 442 U. S. 319 , 325
(1979); Weeks v. United States, 232 U. S. 383 , 389-391
(1914). "'It is a power, that places the liberty of every man in
the hands of every petty officer.'" James Otis, quoted in 2 Works
of John Adams 524 (C. Adams ed. 1850), quoted in turn in Illinois v. Krull, 480 U. S. 340 , 363 (1987)
(O'CONNOR, J., dissenting). The offense to the dignity of the
citizen who is arrested, handcuffed, and searched on a public
street simply because some bureaucrat has failed to maintain an
accurate computer data base strikes me as equally outrageous. In
this case, of course, such an error led to the fortuitous detection
of respondent's unlawful possession of marijuana, and the
suppression of the fruit of the error would prevent the prosecution
of his crime. That cost, however, must be weighed against the
interest in protecting other, wholly innocent citizens from
unwarranted indignity. In my judgment, the cost is amply offset by
an appropriately "jealous regard for maintaining the integrity of
individual rights." Mapp v. Ohio, 367 U. S. 643 , 647
(1961). For this reason, as well as those set forth by JUSTICE
GINSBURG, I respectfully dissent.

															JUSTICE GINSBURG, with whom JUSTICE STEVENS joins,
dissenting.

															This case portrays the increasing use of computer technology in
law enforcement; it illustrates an evolving problem this Court need
not, and in my judgment should not, resolve too hastily. 1 The
Arizona Supreme Court relied on "the

															1 We have in many instances recognized that when frontier legal
problems are presented, periods of "percolation" in, and diverse
opinions from, state and federal appellate courts may yield a
better informed and more enduring final pronouncement by this
Court. See, e. g., McCray v. New 24 principles of a free society" in reaching its decision. This
Court reviews and reverses the Arizona decision on the assumption
that Arizona's highest court sought assiduously to apply this
Court's Fourth Amendment jurisprudence. The Court thus follows the
presumption announced in Michigan v. Long, 463 U. S. 1032 (1983):
If it is unclear whether a state court's decision rests on state or
federal law, Long dictates the assumption that the state
court relied on federal law. On the basis of that assumption, the
Court asserts jurisdiction to review the decision of the Arizona
Supreme Court.

															The Long presumption, as I see it, impedes the States'
ability to serve as laboratories for testing solutions to novel
legal problems. I would apply the opposite presumption and assume
that Arizona's Supreme Court has ruled for its own State and
people, under its own constitutional recognition of individual
security against unwarranted state intrusion. Accordingly, I would
dismiss the writ of certiorari.

															I

															Isaac Evans was arrested because a computer record erroneously
identified an outstanding misdemeanor arrest warrant in his name.
The Arizona Supreme Court's suppression of evidence obtained from
this unlawful arrest did not rest on a close analysis of this
Court's Fourth Amendment precedents. Indeed, the court found our
most relevant decision, United States v. Leon, 468 U. S. 897 (1984), "not helpful." 177 Ariz. 201, 203, 866 P. 2d 869, 871
(1994). Instead, the Arizona court emphasized its comprehension of
the severe curtailment of personal liberty inherent in arrest
warrants. York, 461 U. S. 961, 961-963 (1983) (STEVENS, J.,
respecting denial of petitions for writs of certiorari) ("My vote
to deny certiorari in these cases does not reflect disagreement
with JUSTICE MARSHALL'S appraisal of the importance of the
underlying issue .... In my judgment it is a sound exercise of
discretion for the Court to allow the various States to serve as
laboratories in which the issue receives further study before it is
addressed by this Court."). 25 Specifically, the Arizona Supreme Court saw the growing use of
computerized records in law enforcement as a development presenting
new dangers to individual liberty; excluding evidence seized as a
result of incorrect computer data, the Arizona court anticipated,
would reduce the incidence of uncorrected records: "The dissent laments the 'high costs' of the exclusionary rule,
and suggests that its application here is 'purposeless' and
provides 'no offsetting benefits.' Such an assertion ignores the
fact that arrest warrants result in a denial of human liberty, and
are therefore among the most important of legal documents. I t is
repugnant to the principles of a free society that a person should
ever be taken into police custody because of a computer error
precipitated by government carelessness. As automation increasingly
invades modern life, the potential for Orwellian mischief grows.
Under such circumstances, the exclusionary rule is a 'cost' we
cannot afford to be without." Id., at 204, 866 P. 2d, at
872. Thus, the Arizona court did not consider this case to involve
simply and only a court employee's slip in failing to communicate
with the police, or a police officer's oversight in failing to
record information received from a court employee. That court
recognized a "potential for Orwellian mischief" in the government's
increasing reliance on computer technology in law enforcement. The
Arizona Supreme Court concluded that Leon's distinction
between police conduct and judicial conduct loses force where, as
here, the error derives not from a discretionary judicial function,
but from inattentive recordkeeping. Application of an exclusionary
rule in the circumstances Evans' case presents, the Arizona court
said, "will hopefully serve to improve the efficiency of those who
keep records in our criminal justice system." Ibid. Invoking Long, this Court's majority presumes that the
Arizona Supreme Court relied on federal law. Long in- 26 structs that a state-court opinion discussing both state and
federal precedents shall be deemed to rely on federal law, absent a
plain statement in the opinion that the decision rests on state
law. 463 U. S., at 1040-1042.2 For reasons this case illustrates, I
would choose the opposite plain statement rule. I would presume,
absent a plain statement to the contrary, that a state court's
decision of the kind here at issue rests on an independent
state-law ground.3

															II A

															Widespread reliance on computers to store and convey information
generates, along with manifold benefits, new possibilities of
error, due to both computer malfunctions and operator mistakes.
Most germane to this case, computerization greatly amplifies an
error's effect, and correspondingly intensifies the need for prompt
correction; for inaccurate data can infect not only one agency, but
the many agencies that share access to the data base. The
computerized data bases of the Federal Bureau of Investigation's
National Crime Information Center (NCIC), to take a conspicuous
example, contain

															2 The Long presumption becomes operative when two
conditions are met: (1) the state-court decision must "fairly
appea[r] to rest primarily on federal law, or to be interwoven with
the federal law"; and (2) "the adequacy and independence of any
possible state law ground [must] not [be] clear from the face of
the opinion." 463 U. S., at 1040-1041.

															3 I recognize, in accord with Long on this point, that
there will be cases in which a presumption concerning exercise of
the Court's jurisdiction should yield, i. e., exceptional
instances in which vacation of a state court's judgment and remand
for clarification of the court's decision is in order. See id., at 1041, n. 6 ("There may be certain circumstances in
which clarification is necessary or desirable, and we will not be
foreclosed from taking the appropriate action."); Capital Cities
Media, Inc. v. Toole, 466 U. S. 378 , 379 (1984) (per curiam) (post-Long decision vacating statecourt
judgment and remanding for such further proceedings as the state
court might deem appropriate to clarify the ground of its
decision). 27 over 23 million records, identifying, among other things,
persons and vehicles sought by law enforcement agencies nationwide.
See Hearings before the Subcommittee on the Departments of
Commerce, Justice, and State, the Judiciary, and Related Agencies
of the House Committee on Appropriations, 102d Cong., 2d Sess., pt.
2B, p. 467 (1992). NCIC information is available to approximately
71,000 federal, state, and local agencies. See Hearings before the
Subcommittee on the Departments of Commerce, Justice, and State,
the Judiciary, and Related Agencies of the House Committee on
Appropriations, 103d Cong., 1st Sess., pt. 2A, p. 489 (1993). Thus,
any mistake entered into the NCIC spreads nationwide in an
instant.

															Isaac Evans' arrest exemplifies the risks associated with
computerization of arrest warrants. Though his arrest was in fact
warrantless-the warrant once issued having been quashed over two
weeks before the episode in suit-the computer reported otherwise.
Evans' case is not idiosyncratic. Rogan v. Los
Angeles, 668 F. Supp. 1384 (CD Cal. 1987), similarly indicates
the problem. There, the Los Angeles Police Department, in 1982, had
entered into the NCIC computer an arrest warrant for a man
suspected of robbery and murder. Because the suspect had been
impersonating Terry Dean Rogan, the arrest warrant erroneously
named Rogan. Compounding the error, the Los Angeles Police
Department had failed to include a description of the suspect's
physical characteristics. During the next two years, this incorrect
and incomplete information caused Rogan to be arrested four times,
three times at gunpoint, after stops for minor traffic infractions
in Michigan and Oklahoma. See id., at 13871389.4 In another
case of the same genre, the District Court observed:

															4 See also Finch v. Chapman, 785 F. Supp. 1277,
1278-1279 (ND Ill. 1992) (misinformation long retained in NCIC
records twice caused plaintiff's arrest and detention), affirmance
order, 991 F.2d
799 (CA7 1993). 28 "Because of the inaccurate listing in the NCIC computer,
defendant was a 'marked man' for the five months prior to his
arrest .... At any time ... a routine check by the police could
well result in defendant's arrest, booking, search and detention
.... Moreover, this could happen anywhere in the United States
where law enforcement officers had access to NCIC information.
Defendant was subject to being deprived of his liberty at any time
and without any legal basis." United States v. Mackey, 387 F. Supp. 1121, 1124 (Nev. 1975).

															In the instant case, the Court features testimony of the Chief
Clerk of the Justice Court in East Phoenix to the effect that
errors of the kind Evans encountered are reported only "on[c]e
every three or four years." Ante, at 15 (citing App. 37).
But the same witness also recounted that, when the error concerning
Evans came to light, an immediate check revealed that three other
errors of the very same kind had occurred on "that same day." See ante, at 21-22, and n. 3 (STEVENS, J., dissenting).

															B

															This Court and the Arizona Supreme Court hold diverse views on
the question whether application of an exclusionary rule will
reduce the incidence of erroneous computer data left without prompt
correction. Observing that "court clerks are not adjuncts to the
law enforcement team engaged in the often competitive enterprise of
ferreting out crime," the Court reasons that "there is no basis for
believing that application of the exclusionary rule in these
circumstances will have a significant effect on court employees
responsible for informing the police that a warrant has been
quashed." Ante, at 15. In the Court's view, exclusion of
evidence, even if capable of deterring police officer errors,
cannot deter the 29 carelessness of other governmental actors.5 Whatever federal
precedents may indicate-an issue on which I voice no opinion-the
Court's conclusion is not the lesson inevitably to be drawn from
logic or experience.

															In this electronic age, particularly with respect to
recordkeeping, court personnel and police officers are not neatly
compartmentalized actors. Instead, they serve together to carry out
the State's information-gathering objectives. Whether particular
records are maintained by the police or the courts should not be
dispositive where a single computer data base can answer all calls.
Not only is it artificial to distinguish between court clerk and
police clerk slips; in practice, it may be difficult to pinpoint
whether one official, e. g., a court employee, or
another, e. g., a police officer, caused the error to
exist or to persist. Applying an exclusionary rule as the Arizona
court did may well supply a powerful incentive to the State to
promote the prompt updating of computer records. That was the
Arizona Supreme Court's hardly unreasonable expectation. The
incentive to update promptly would be diminished if court-initiated
records were exempt from the rule's sway.

															5 It has been suggested that an exclusionary rule cannot deter
carelessness, but can affect only intentional or reckless
misconduct. This suggestion runs counter to a premise underlying
all of negligence law-that imposing liability for negligence, i. e., lack of due care, creates an incentive to act with
greater care.

															That the mistake may have been made by a clerical worker does
not alter the conclusion that application of the exclusionary rule
has deterrent value. Just as the risk of respondeat superior liability encourages employers to supervise more closely their
employees' conduct, so the risk of exclusion of evidence encourages
policymakers and systems managers to monitor the performance of the
systems they install and the personnel employed to operate those
systems. In the words of the trial court, the mistake in Evans'
case was "perhaps the negligence of the Justice Court, or the
negligence of the Sheriff's office. But it is still the negligence
of the State." App. 51. 30 C

															The debate over the efficacy of an exclusionary rule reveals
that deterrence is an empirical question, not a logical one. "It is
one of the happy incidents of the federal system that a single
courageous State may, if its citizens choose, serve as a
laboratory; and try novel social and economic experiments without
risk to the rest of the country." New State Ice Co. v. Liebmann, 285
U. S. 262 , 311 (1932) (Brandeis, J., dissenting). With that
facet of our federalism in mind, this Court should select a
jurisdictional presumption that encourages States to explore
different means to secure respect for individual rights in modern
times.

															Historically, state laws were the source, and state courts the
arbiters, of individual rights. Linde, First Things First:

															Rediscovering the States' Bills of Rights, 9 U. BaIt. L. Rev.
379, 382 (1980). The drafters of the Federal Bill of Rights looked
to provisions in state constitutions as models. Id., at 381.
Moreover, many States that adopted constitutions after 1789 modeled
their bills of rights on pre-existing state constitutions, rather
than on the Federal Bill of Rights. Ibid. And before this
Court recognized that the Fourteenth Amendment-which constrains
actions by States-incorporates provisions of the Federal Bill of
Rights, state constitutional rights, as interpreted by state
courts, imposed the primary constraints on state action. Brennan,
State Constitutions and the Protection of Individual Rights, 90
Harv. L. Rev. 489, 501-502 (1977).

															State courts interpreting state law remain particularly well
situated to enforce individual rights against the States.
Institutional constraints, it has been observed, may limit the
ability of this Court to enforce the federal constitutional
guarantees. Sager, Fair Measure: The Legal Status of Underenforced
Constitutional Norms, 91 Harv. L. Rev. 1212, 1217-1218 (1978).
Prime among the institutional constraints, this Court is reluctant
to intrude too deeply into areas traditionally regulated by the
States. This aspect of 31 federalism does not touch or concern state courts interpreting
state law.

															III

															Under Long, when state courts engage in the essential
process of developing state constitutional law, they may insulate
their decisions from this Court's review by means of a plain
statement of intent to rest upon an independent state ground. The
plain statement option does not, however, make pleas for
reconsideration of the Long presumption much ado about
nothing.6 Both on a practical and on a symbolic level, the
presumption chosen matters.

															The presumption is an imperfect barometer of state courts'
intent. Although it is easy enough for a state court to say the
requisite magic words, the court may not recognize that its opinion
triggers Long's plain statement requirement. "[A]pplication
of Long's presumption depends on a whole series of 'soft'
requirements: the state decision must 'fairly appear' to rest
'primarily' on federal law or be 'interwoven' with federal law, and
the independence of the state ground must be 'not clear' from the
face of the state opinion. These are not self-applying concepts."
P. Bator, D. Meltzer, P. Mishkin, & D. Shapiro, Hart and
Wechsler's The Federal Courts and the Federal System 552 (3d ed.
1988) (hereinafter Hart and Wechsler); cf. Coleman v. Thompson, 501
U. S. 722 , 735-740 (1991) (declining to apply Long presumption to summary dismissal order).

															Can the highest court of a State satisfy Long's "plain
statement" requirement in advance, through a blanket disclaimer?
The New Hampshire Supreme Court, for example, has declared: "We
hereby make clear that when this court cites federal or other State
court opinions in construing provisions of the New Hampshire
Constitution or statutes, we 6 Long has generated many pages of academic
commentary, some supportive, some critical of the presumption. See, e. g., P. Bator, D. Meltzer, P. Mishkin, & D.
Shapiro, Hart and Wechsler's The Federal Courts and the Federal
System 553, n. 3 (3d ed. 1988) (citing commentary). 32 rely on those precedents merely for guidance and do not consider
our results bound by those decisions." State v. Ball, 124 N. H. 226, 233, 471 A. 2d 347, 352 (1983). See also State v. Kennedy, 295 Ore. 260, 267, 666 P. 2d 1316,
1321 (1983) ("Lest there be any doubt about it, when this court
cites federal opinions in interpreting a provision of Oregon law,
it does so because it finds the views there expressed persuasive,
not because it considers itself bound to do so by its understanding
of federal doctrines."). This Court's stated reluctance to look
beneath or beyond the very state-court opinion at issue in order to
answer the jurisdictional question, see Long, 463 U. S., at
1040, may render such blanket declarations ineffective. Cf. Hart
and Wechsler 553 ("[T]he Court's protestations-that its presumption
shows greater respect for state courts than asking them to clarify
their opinions-ring hollow: Long simply puts the burden of
clarification on the state court in advance.").

															Application of the Long presumption has increased the
incidence of nondispositive United States Supreme Court
determinations-instances in which state courts, on remand, have
reinstated their prior judgments after clarifying their reliance on
state grounds. Westling, Advisory Opinions and the
"Constitutionally Required" Adequate and Independent State Grounds
Doctrine, 63 Tulane L. Rev. 379, 389, and n. 47 (1988)
(pre-Long, i. e., between January 1, 1978, and June 30,
1983, 14.3% of decisions (2 of 14) involving potentially adequate
and independent state grounds were reinstated on state grounds upon
remand; post-Long, i. e., between July 1, 1983, and
January 1, 1988, 26.7% of such decisions (4 of 15) were reinstated
on remand). Even if these reinstatements do not render the Supreme
Court's opinion technically "advisory," see Hart and Wechsler 537,
they do suggest that the Court unnecessarily spent its resources on
cases better left, at the time in question, to state-court
solution.

															The Long presumption, in sum, departs from the
traditional understanding that "every federal court is 'without 33 jurisdiction' unless 'the contrary appears affirmatively from
the record.'" Delaware v. Van Arsdall, 475 U. S. 673 , 692 (1986)
(STEVENS, J., dissenting) (quoting King Bridge Co. v. Otoe County, 120 U. S. 225 , 226
(1887)). And it is out of sync with the principle that this Court
will avoid constitutional questions when an alternative basis of
decision fairly presents itself. Ashwander v. TVA, 297 U. S. 288 ,
346-347 (1936) (Brandeis, J., concurring). Most critically, as this
case shows, the Long presumption interferes prematurely with
state-court endeavors to explore different solutions to new
problems facing modern society.

															I recognize that "[s]ince Long, we repeatedly have
followed [its] 'plain statement' requirement," Harris v. Reed, 489 U.
S. 255 , 261, n. 7 (1989), and that precedent ought not be
overruled absent strong cause. But the Long ruling itself
did "a virtual about-face regarding the guidelines for determining
the reviewability of state court decisions in situations where the
state court opinion is not absolutely clear about the bases on
which it rests. The traditional presumption was that the Court
lacked jurisdiction unless its authority to review was clear on the
face of the state court opinion. When faced with uncertainty, the
Court in the past occasionally remanded such cases to the state
court for clarification. But more commonly, the Court would deny
jurisdiction where there was uncertainty." G. Gunther,
Constitutional Law 56 (12th ed. 1991). Restoring a main rule "deny[ing] jurisdiction where there [is]
uncertainty," ibid., would stop this Court from asserting
authority in matters belonging, or at least appropriately left, to
the States' domain. Cf. Erie R. Co. v. Tompkins, 304 U. S. 64, 77-80 (1938). Recognizing that "adequate state grounds
are independent unless it clearly appears other- 34 wise," Long, 463 U. S., at 1066 (STEVENS, J.,
dissenting),7 would also avoid premature settlement of important
federal questions. The submission for the United States is telling
in this regard. While filing in support of petitioner, the United
States acknowledges the problem occasioned by "erroneous
information contained in law enforcement computer-information
systems," but does not see this case as a proper vehicle for a
pathmarking opinion. The United States suggests that the Court
"await a case in which relevant characteristics of such systems and
the legal questions they pose can be thoroughly explored." Brief
for United States as Amicus Curiae 13. ***

															The Arizona Supreme Court found it "repugnant to the principles
of a free society," 177 Ariz., at 204, 866 P. 2d, at 872, to take a
person "into police custody because of a computer error
precipitated by government carelessness." Ibid. Few, I
believe, would disagree. Whether, in order to guard against such
errors, "the exclusionary rule is a 'cost' we cannot afford to be
without," ibid., seems to me a question this Court should
not rush to decide. The Court errs, as I see it, in presuming that
Arizona rested its decision on federal grounds. I would abandon the Long presumption and dismiss the writ because the generally
applicable obligation affirmatively to establish the Court's
jurisdiction has not been satisfied.

															7 For instances in which a state court's decision, even if
arguably placed on a state ground, embodies a misconstruction of
federal law threatening gravely to mislead, or to engender
disuniformity, confusion, or instability, a Supreme Court order
vacating the judgment and remanding for clarification should
suffice. See Hart and Wechsler 554; see also supra, at 26,
n.3.