UNITED STATES OF AMERICA, PETITIONER V. ALBERTO ANTONIO LEON, ET
AL.  COMMONWEALTH OF MASSACHUSETTS, PETITIONER V. OSBORNE SHEPPARD.
STATE OF COLORADO, PETITIONER V. FIDEL QUINTERO

   No. 82-1771

   No. 82-963

   No. 82-1711

   In the Supreme Court of the United States

   October Term, 1983

   On Writs of Certiorari to the United States Court of Appeals for
the Ninth Circuit, the Supreme Judicial Court of Massachusetts, and
the Supreme Court of Colorado

   Brief for the United States

                       PARTIES TO THE PROCEEDING

   In addition to the parties shown by the caption in No. 82-1771,
Armando Lazaro Sanchez, Patsy Ann Stewart and Ricardo Albert Del
Castillo were appellees below and are respondents here.

                           TABLE OF CONTENTS

   Opinions below
   Jurisdiction
   Statement
   Summary of argument
   Argument:
      I. As a judicially created rule of evidence,
      the exclusionary rule may appropriately be modified
      in the light of experience
      A. The only viable justification for the exclusionary
      rule is its presumed deterrent effect on unlawful
      police conduct
      B. The policy of deterrence dictates a cost-benefit
      approach to the application of the exclusionary rule
      II. The costs of the exclusionary rule outweigh
      its benefits when it is applied to suppress evidence
      obtained in a search and seizure that a reasonably
      well-trained officer would not have recognized as a
      violation of the Fourth Amendment
      A. The presumed benefits of the exclusionary
      rule are not realized by applying it to suppress
      evidence obtained in searches or seizures that were
      not recognizably violative of the Fourth Amendment
      B. The reasons for applying the exclusionary rule
      are most remote when law enforcement officers have
      relied on a judicially-issued search warrant
      C. In light of the exclusionary rule's inability
      to fulfill its deterrent purpose when applied to
      reasonable mistakes, its costs are higher than our
      system of criminal justice can afford
      D. The objections to a reasonable mistake exception
      to the exclusionary rule are insufficient to overcome
      the need for modification
   Conclusion

                            OPINIONS BELOW

   The opinion of the court of appeals (Pet. App. 1a-6a) and the
ruling of the district court suppressing evidence (id. at 9a-14a) are
unreported.

                             JURISDICTION

   The judgment of the court of appeals was entered on January 19,
1983 (Pet. App. 7a).  A petition for rehearing was denied on March 4,
1983 (id. at 8a).  The petition for a writ of certiorari was filed on
April 29, 1983, and granted on June 27, 1983 (J.A. 151).  The
jurisdiction of this Court rests on 28 U.S.C. 1254(1).

                          QUESTIONS PRESENTED

   1. In No. 82-1771, the question presented is whether the Fourth
Amendment exclusionary rule should be modified so as not to bar the
admission of evidence seized in reasonable reliance on a search
warrant that is subsequently held to be defective for lack of probable
cause.

   2. In No. 82-963, the question presented is whether the Fourth
Amendment exclusionary rule should be modified so as not to bar the
admission of evidence seized in reasonable reliance on a search
warrant supported by probable cause but later held to be technically
defective for failure to incorporate the specification of items to be
seized contained in the warrant application.

   3. In No. 82-1711, the question presented is whether the Fourth
Amendment exclusionary rule should be modified so as not to bar the
admission of evidence seized in the reasonable belief that the
warrantless arrest of a burglary suspect did not violate the Fourth
Amendment.

   The Solicitor General, on behalf of the United States, submits this
brief for the United States as petitioner in No. 82-1771 and as amicus
curiae in support of the petitioners in Nos. 82-963 and 82-1711.  /1/

                               STATEMENT

   1. No 82-1771 -- On October 2, 1981, a five-court indictment was
returned in the United States District Court for the Central District
of California charging respondents with conspiring to possess and
distribute cocaine, in violation of 21 U.S.C. 846 (Count I) (J.A.
27-29).  In addition, respondents were variously charged in
substantive counts with the possession of cocaine (Counts II, III and
V) and methaqualone (Court IV) with intent to distribute, in violation
of 21 U.S.C. 841(a)(1) (J.A. 29-30).  Respondents thereafter moved to
suppress contraband and other evidence seized pursuant to a judicial
warrant authorizing the search of residences and automobiles belonging
to them.  Following an evidentiary hearing, the district court granted
the motion to suppress in part, finding that the search warrant was
not supported by probable cause (Pet. App. 10a).  /2/ The court of
appeals affirmed the suppression order, with one judge dissenting (id.
at 1a-6a).

   a. The affidavit in support of the search warrant contained the
following information.  On August 18, 1981, a confidential informant
of unproven reliability told Officer Cyril A. Rombach of the Burbank,
California, Police Department that two persons known to him as
"Armando" and "Patsy" were selling large quantities of cocaine and
methaqualone (quaaludes) from their residence at 620 Price Drive in
Burbank (J.A. 37).  According to the informant, "Armando" sold cocaine
in quantities of one-half pound and larger, and "Patsy" sold
methaqualone in quantities of 100 tablets and larger (ibid.).  The
informant also stated that he had been present at the Price Drive
residence five months earlier and had at that time seen "Patsy" sell
500 methaqualone tablets (ibid.).  At the same time, the informant
observed a shoe box containing between $50,000 and $100,000 that
belonged to "Patsy." Finally, the informant stated that "Patsy" and
"Armando" kept only relatively small quantities of drugs at the Price
Drive residence, storing the remainder at another location somewhere
in the "hill area" of Burbank (ibid.).

   On receipt of this information, Burbank police officers instituted
a month-long investigation that first focused on the Price Drive
residence and later on residences located at 716 South Sunset Canyon
in Burbank and 7902 Via Magdelena in Los Angeles.  On August 19, 1981,
officers drove to the Price Drive residence and observed automobiles
registered to respondents Armando Sanchez and Patsy Ann Stewart parked
outside (J.A. 37-38).  Although a records check revealed that Stewart
had no prior criminal record, Sanchez had been found with $20,000 in
currency at the Miami Airport in 1977, and had been arrested in Miami
in December 1978 for possession of marijuana (J.A. 38).

   On August 24, 1981, officers observed the arrival at the Price
Drive residence of an automobile registered to respondent Del Castillo
(J.A. 38).  A Latin male exited the vehicle, entered the house,
returned to the vehicle ten minutes later carrying a small paper bag
and drove away.  A background check disclosed that in January 1979 Del
Castillo had been arrested in Miami for possession of 50 pounds of
marijuana while he was attempting to board an aircraft bound for Los
Angeles (J.A. 39).  The telephone number for his employer that Del
Castillo had given the probation authorities turned out to be
registered to respondent Leon.  Leon, in turn, had been arrested in
1980 on cocaine and quaalude charges and in 1979 on quaalude charges
(ibid.).  In addition, police officers were told by a woman, who
previously had been arrested with Leon, that Leon was a drug importer
affiliated with the "Cuban Mafia" (J.A. 39-40), and by a second
informant that Leon had several thousand quaalude tablets at his
residence (J.A. 40).  Utility records showed that Leon lived at 716
South Sunset Canyon in Burbank (ibid.).

   On August 25, 1981, officers observed Thomas Kilburn enter the
Price Drive house and emerge a short while later carrying a paper bag
(J.A. 40-41).  The officers determined that Kilburn had been arrested
in 1974 for possession of hashhish and cultivation of marijuana (J.A.
41).  On August 26, 1981, the officers observed an unidentified
individual enter the Price Drive residence and emerge a short time
later carrying a small box (ibid.).

   On August 28, 1981, officers observed Del Castillo's vehicle being
driven from Price Drive to a condominium at 7902 Via Magdelena.  Later
that day, Sanchez drove in his vehicle from Price Drive to Leon's
Sunset Canyon residence, where Sanchez obtained a small package and
returned to Price Drive.  Later, an unidentified man drove to the
Price Drive residence and entered the house.  At about the same time,
a man driving Del Castillo's vehicle arrived, ran into the residence,
and ran back out immediately.  Sanchez then left the Price Drive
house, drove to a neighboring town, parked his car, and entered an
unknown house.  Before surveillance was lost, Sanchez was observed
returning to his car with a large rectangular container (J.A. 42-43).

   On September 8, 1981, officers were engaged in the surveillance of
another house as part of a separate drug investigation.  They observed
Patsy Stewart drive up to the house.  A female left the house and
entered Stewart's vehicle.  One minute later, she returned to the
house carrying a small paper sack.  Later that day, the occupants of
that house were arrested for purchasing amphetamines from persons not
related to this case (J.A. 43).

   On September 11, 1981, the officers saw Sanchez and Stewart drive
to the Los Angeles airport, where Sanchez, carrying only a small
briefcase and a garment bag, boarded a flight for Miami (J.A. 44).
Four days later, Stewart was driven to the airport in Del Castillo's
automobile.  Visibly upset when told that she could not carry a large
suitcase on the plane with her, Stewart checked the bag and boarded a
flight for Miami (J.A. 46-47).  Stewart and Sanchez both returned to
Los Angeles on September 19, 1981.  Although they had been seated
together on the plane, Stewart and Sanchez deplaned and walked through
the terminal separately;  they rejoined one another only near the exit
to the terminal.  The pair carried many pieces of carry-on luggage,
most of which they had not taken to Miami.  And, although they had
checked at least one piece of luggage in Miami, they did not pick up
any checked luggage in Los Angeles.  Nor did either of them have the
large suitcase that Stewart had taken with her to Florida (J.A.
48-49).  As they were entering a taxi, the two were approached by
airport narcotics officers who conducted a consensual search of their
luggage.  A small amount of marijuana was found (J.A. 49).

   In the early morning hours of September 19, 1981, the officers saw
a silver Chevrolet that was registered to Sanchez parked in front of
Leon's house on Sunset Canyon.  The vehicle was later seen at the
Price Drive residence (J.A. 49).  The officers then went to 7902 Via
Magdelena, where they observed the interior lights on.  This was the
first time since the beginning of the investigation that the officers
had seen any sign of occupancy at the condominium.  /3/ Two days
later, on September 21, Sanchez's automobile was observed parked
outside the condominium (J.A. 50).

   From these observations, Officer Rombach concluded that respondents
were engaged in an on-going criminal enterprise involving the
transportation and distribution of controlled substances (J.A. 52).
Officer Rombach based his opinion both on personal experience as a
narcotics officer and on specialized training in narcotics
investigations (J.A. 50-52).  In addition, Officer Rombach opined that
the Via Magdelena condominium was being used as a "stash pad" to store
large quantities of narcotics, which were then transported in smaller
amounts to respondents' residences for distribution (J.A. 47-48).
Officer Rombach averred that major drug dealers most often store large
quantities of drugs at locations other than their primary residences
to minimize the risk of seizure if their activities are detected
(ibid.).

   b. Based on this information, a state superior court judge issued a
warrant on September 21, 1981, authorizing the search of the
residences at 620 Price Drive and 716 South Sunset Canyon, the
condominium at 7902 Via Magdelena, and automobiles registered to
Sanchez, Stewart, Leon and Del Castillo (J.A. 31-33).  In an ensuring
series of searches, police officers seized more than four pounds of
cocaine and 1,165 quaalude tablets at the Via Magdelena condominium,
nearly a pound of cocaine at Leon's house on Sunset Canyon, and about
an ounce of cocaine at the Price Drive residence of Stewart and
Sanchez.  The officers additionally found paraphernalia for testing,
cutting and packaging cocaine, scales, a police radio and large
amounts of currency (J.A. 53-69).  Finally, a search of Stewart's
automobile produced two garage door openers -- one for the Price Drive
residence and one for the Via Magdelena condominium -- while a search
of Del Castillo's automobile revealed a small amount of marijuana
residue.

   c. The district court suppressed the seized evidence, finding that
there was "no question" that the reliability and credibility of the
informant had not been established (Pet. App. 10a).  Although
recognizing that "(s)ome details * * * tended to corroborate" the
informant's information, the court concluded that such details either
corroborated information about a stale transaction or were "as
consistent with innocence as * * * with guilt" (ibid.).  Accordingly,
the court found that the search warrant was not supported by probable
cause.  /4/

   The district court rejected the government's argument that the
exclusionary rule should not apply when evidence is seized in
reasonable, good-faith reliance on a search warrant (Pet. App. 14a).
In so doing, however, the district court specifically noted (ibid.):

         I will say certainly in my view, there is not any question
      about good faith.  He (Officer Rombach) went to a Superior Court
      judge and got a warrant;  obviously laid a meticulous trail.
      Had surveilled for a long period of time, and I believe his
      testimony -- and I think he said he consulted with three Deputy
      District Attorneys before proceeding himself, and I certainly
      have no doubt about the fact that that is true.

   d. On appeal, a panel of the Ninth Circuit affirmed the suppression
order, with one judge dissenting.  The majority held that the only
portion of the affidavit that adequately set forth facts to
demonstrate the informant's knowledge of criminal activity -- the
informant's personal observation of "Patsy's" distribution of drugs --
was fatally stale (Pet. App. 3a).  The majority further held that the
information supplied by the informant was inadequate under both prongs
of the Aguilar-Spinelli test /5/ and that the month-long independent
police investigation was insufficient either to corroborate the
informant's information or to revive the stale information (Pet. App.
3a).  Finally, the majority flatly declined to recognize a
"good-faith" exception to the exclusionary rule (id. at 4a).

   In dissent, Judge Kennedy observed that "(t)he affidavit for the
search warrant sets forth the details of a police investigation
conducted with care, diligence, and good faith" (Pet. App. 5a).  Judge
Kennedy concluded that the informant's information was both adequately
corroborated and sufficiently current in view of the month-long
surveillance, which had revealed to experienced investigators a
continuous pattern of conduct that "was quite inconsistent with any
explanation other than illegal drug activity" (ibid.).

   2. No. 82-963 -- On May 5, 1979, at approximately 5 a.m., the badly
burned and beaten body of a 29-year old woman was found in a vacant
lot in the Roxbury section of Boston (82-963 Pet. App. A3).
Respondent was convicted of first-degree murder (id. at A1).  On
appeal, the Supreme Judicial Court of Massachusetts reversed
respondent's conviction because certain evidence introduced at trial
had been "obtained in the course of a police search conducted in good
faith, but pursuant to a warrant which, although issued on probable
cause, violated the constitutional and statutory requirement that
search warrants describe the things to be seized" (ibid.).

   a. After the murder victim's body was discovered, suspicion quickly
focused on respondent, a boyfriend of the victim (82-963 Pet. App.
A4).  Respondent voluntarily accompanied police officers to the
station for questioning (id. at A4-A5).  On the way to the station,
respondent told police that he had last seen the victim some five days
earlier, that on that day he had gone to her house, stayed there for
about an hour, and then left with her in a cab (id. at A5).  They
stopped to purchase some marijuana and a bottle of amaretto (id. at
A6).  Respondent told police that the victim then left him at about 1
p.m. and that he had not seen her since (ibid.).  At the police
station, respondent told essentially the same story, adding that after
purchasing the marijuana and the amaretto he and the victim had gone
to respondent's home at 42 Deckard Street in Roxbury and that the
victim stayed there until approximately 2 p.m. (id. at A6-A7).
Respondent also told the police that he had spent the evening of May 4
and the early morning hours of May 5, when the victim's body was
found, at a "gambling house" in Dorchester (id. at A8).

   The police interviewed various persons who, according to
respondent, had been at the "gaming house" when he was there.  The
police learned that at about 3 a.m. on May 5, respondent had borrowed
a car for a trip that should have taken approximately 15 minutes, but
that he did not return to the "gaming house" until approximately 4:45
a.m.  He remained there for only a few minutes and then left again
(82-963 Pet. App. A8).

   Continuing their investigation on Sunday morning, May 6, 1979,
police learned from a friend of respondent that the basement of the
Deckard Street house had been refinished and that respondent had said
he entertained women there (82-963 Pet. App. A9).  With the owner's
consent, police then inspected the car that respondent had borrowed
the previous night.  The found bloodstains and pieces of hair on the
rear bumper and near the lid of the trunk (id. at A10).  Inside the
car were various types of wire (ibid.).

   Later on Sunday morning, the police and the district attorney
concluded that they should seek a warrant for respondent's arrest and
a warrant to search his residence at Deckard Street (82-963 Pet. App.
A10).  An application for a search warrant was prepared by one of the
investigating officers, and both the district attorney and his first
assistant concluded that it set forth probable cause for the arrest
and the search (id. at A11).  The application specified precisely
those items for which permission to search would be sought (id. at A12
n.7):

         A fifth bottle of amaretto liquor, 2 nickel bags of
      marijuana, a woman's jacket that has been described as
      black-grey (charcoal), any possessions of Sandra D. Boulware,
      similar type wire and rope that match those in the body of
      Sandra D. Boulware, or in the above Thunderbird.  A blunt
      instrument that might have been used on the victim, men's or
      women's clothing that may have blood, gasoline burns on them.
      Items that may have fingerprints of the victim.

   At this point, on Sunday afternoon, no court clerk could be found,
nor could the police find a suitable search warrant form.  The best
they were able to locate was a form once used for searches for
controlled substances in the Dorchester Division of the Municipal
Court (82-963 Pet. App. A13).  One of the officers attempted to modify
this printed form by crossing out the words "controlled substance" on
one side of the form and replacing the word "Dorchester" with
"Roxbury" (ibid.).  He also inserted "2nd & Basement" of 42 Deckard
Street as the places to be searched (ibid.).  Despite these changes
and additions, the references to "controlled substance" in those
portions of the form that constituted the application for a search
warrant and, when signed, would become the warrant itself, were not
deleted (id. at A13-A14).

   Several police officers and the first assistant district attorney
then went to the home of a judge, arriving at approximately 2:45 p.m.
on Sunday afternoon.  The judge was unable to find a suitable search
warrant form in his library, and so he used the "controlled substance"
form as modified by the police and by himself.  Again, however, no
change was made to the substantive portion of the warrant.  Thus, the
warrant authorized the police "to search for any controlled substance,
article, implement or other paraphernalia used in, for, or in
connection with the unlawful possession or use of any controlled
substance" (82-963 Pet. App. A15).  The warrant did not refer to the
items listed in the police officer's affidavit in support of the
application, nor was the affidavit attached to the search warrant
(ibid.).

   One of the officers left with the warrant and his own affidavit in
support thereof (82-963 Pet. App. A16).  He thought the warrant was
valid (ibid.).  At about 5 p.m. on Sunday afternoon, he arrived at 42
Deckard Street to execute the warrant.  He was admitted to the house
by the respondent's mother and sister, neither of whom apparently
asked to read the warrant (id. at A16-A17).

   During the course of the search, the police found and seized
apparently bloodstained boots, women's earrings, one apparently with
bloodstains, an apparently bloodstained envelope, a pair of apparently
bloody men's jockey shorts and women's leotards.  The police also
found bloodstains on the concrete floor of the cellar that later were
shown to match the victim's blood type (82-963 Pet. App. A17-A20).
The Supreme Judicial Court of Massachusetts summed up the evidentiary
significance of the search as follows (id. at A20-A21):

         It can readily be seen that evidence seized in the search of
      42 Deckard Street tended to show that the (respondent) seriously
      injured the victim in his cellar, hid her earrings under a piece
      of plywood under a mat, and tied her up with wire available in
      cellar of his home.  This evidence, much of it obtained as a
      result of careful and commendable police investigatory
      techniques, was highly probative of the (respondent's) guilt.
      Although the Commonwealth could have presented a case against
      the (respondent) without this evidence, this evidence was most
      important in rounding out a case based only on circumstantial
      evidence.

   b. The trial court denied respondent's motion to suppress the
evidence seized at 42 Deckard Street (82-963 Pet. App. B1-B48).  The
court first held that the affidavit in support of the search warrant
established probable cause to search the premises at 42 Deckard Street
(id. at B26-B29).  The court then held, however, that the warrant was
"fatally defective" (id. at B34) because it did not incorporate by
reference or have attached to it the application for the warrant,
which, the court found, adequately specified the places to be searched
and the items to be seized.  Nevertheless, the trial judge concluded
that the exclusionary rule should not be invoked because its deterrent
effect would not be realized (id. at B42-B44):

         In this case the police sought a warrant.  The affidavit was
      submitted to an official from the District Attorney's office for
      a determination as to its adequacy from the point of view of
      probable cause.  There was proper presentment to a magistrate.
      There was an independent assessment of that disinterested
      judicial officer that there was probable cause to search.  The
      policy had adequately described with constitutional specificity
      the places to be searched and the items to be seized.  The
      police presented a form which was the only form of warrant
      available to them.  The magistrate said he could adopt it.
      Thereafter the actual search undertaken was within the limit of
      the authority the police thought reasonably had been granted.

                      * * *

         (I)f police officers undertake their duties properly, they
      will act in the same fashion in similar circumstances in the
      future and the only consequence of applying the exclusionary
      rule would be to keep from the jury probative evidence and
      thereby impair the truth finding function.

   c. The Supreme Judicial Court of Massachusetts reversed (82-963
Pet. App. A30-A53).  A plurality of the court first held that the
warrant was defective for failing to specify the items to be seized
(id. at A30-A34).  After noting that few courts had addressed the
applicability of the exclusionary rule to situations involving
judicial error rather than police misconduct, the plurality opinion
concluded that suppression was of dubious validity as a deterrent "in
cases where the police conduct was entirely proper, the defendant was
not prejudiced by the magistrate's error, and an appellate court
clearly identifies the magistrate's error of law as a guide to future
conduct" (id. at A48-A49).  Nevertheless, the plurality concluded that
suppression was required in this case because this Court has not yet
recognized an exception to the exclusionary rule for an error of the
type that occurred here (id. at A49-A52).

   Two justices concurred in the judgment because, in their view, the
search warrant was so defective that neither the police nor the
issuing judge could be said to have acted in reasonable good faith
(82-963 Pet. App. A5-A12).  The concurring justices also disagreed
with the plurality on the efficacy of the exclusionary rule as a means
for deterring judicial error (id. at A14).

   Justice Lynch dissented.  First, he noted that, the technical
defect notwithstanding, the search warrant in this case posed none of
the dangers of general warrants and that the police had in fact
conducted the search as if the items to be seized had been
specifically identified in the warrant (82-963 Pet. App. A2-A5).  More
importantly, the dissent concluded that application of the
exclusionary rule in this case would "serve no beneficial purpose"
(id. at A11):

         Police misconduct will not be deterred because none occurred.
       The human error committed by the judge harmed no rights of the
      defendant, as nothing beyond the evidence listed in the
      affidavit was searched for or seized.  By contrast, application
      of the exclusionary rule will result in the very substantial
      harm of withdrawing highly probative evidence from the trier of
      fact.

   Accordingly, the dissent concluded that this Court's exclusionary
rule precedents did not mandate suppression in this case (id. at A12).

   3. No. 82-1711 -- Respondent was convicted of second degree
burglary.  Following his conviction, the trial court granted his
motion for a new trial and his motion to suppress evidence in light of
an intervening decision of the Supreme Court of Colorado, People v.
Schreyer, 640 P.2d 1147 (1982).  On the State's appeal, the state
supreme court affirmed the suppression ruling, holding that the police
lacked probable cause to arrest respondent and that evidence seized
from respondent at the time of his arrest was therefore inadmissible
at his burglary trial.  The court also declined to recognize a "good
faith" exception to the exclusionary rule because this Court has not
yet done so (82-1711 Pet. App. 7);  it further held that Colorado's
statutory good faith exception (Colo. Rev. Stat. Section 16-3-308
(Supp. 1982)) did not apply to this case.

   a. On September 29, 1981, Darlene Bergan was outside her home in
Denver sweeping the porch.  She saw a man walking on the opposite side
of the street and observed him briefly peering into the front window
of the house across from hers.  After observing him apparently looking
into other windows at the same house, she saw him stop at another
house, after which he disappeared from her view.  She next saw him
about an hour later at a bus stop next to her house.  He had taken off
his shirt and was using it to cover a television set.  He appeared
nervous to Mrs. Bergan, and she called the police (82-1711 Pet. App.
3).

   Officer Freeman, a 21-year police veteran, was the first to respond
to the dispatcher's report of a possible burglary suspect.  He asked
respondent for identification, but respondent had none.  Other
officers then arrived at the scene.  They asked respondent various
questions, to which he responded that he had bought the television set
from someone in the neighborhood for $100 and was trying to take it
home.  He was wearing an undershirt and had brown wool gloves in his
back pocket (82-1711 Pet. App. 4).

   After Mrs. Bergan came outside the identified herself as the person
who had called the police, respondent was arrested and searched
(82-1711 Pet. App. 4).  Under his shirt, police found the television
set and a video game.  They also found $140 in cash, five rings
(including two class rings bearing different initials and class
years), and some women's jewelry in respondent's pockets (id. at 4-5).

   Several hours after respondent was arrested, the owners of a house
one block south of Mrs. Bergan's house reported that their house had
been burglarized and that a television set and a video game had been
stolen.  The television set and video game that had been found in
respondent's possession were later identified as the items taken in
the burglary (82-1711 Pet. App. 5).

   b. A majority of the state supreme court held that the officers
lacked probable cause to arrest respondent because they did not learn
until several hours after the arrest that a burglary had in fact been
committed.  As the majority explained (82-1711 Pet. App. 6-7):

         The arresting officer in this case believed that probable
      cause existed to arrest Quintero.  At the time the arrest was
      made, the police knew that Quintero was a stranger to the
      neighborhood, and that he claimed that he had purchased a
      television set from someone in the neighborhood.  They also knew
      that he had attempted to cover the television set and the video
      game with his shirt.  He had no identification, but no evidence
      existed to establish that a crime had been committed.  Brown v.
      Texas, 443 U.S. 47 * * * (1979).  The police did not learn who
      the owners of the television set and the video game were until
      more than five hours after they arrested Quintero.  Suspicion
      does not amount to probable cause and an analysis of the facts
      requires us to reach the same conclusion which we reached in
      People v. Schreyer, 640 P.2d 1147 (Colo. 1982).

   The majority also held that the lack of probable cause to arrest
was not remedied by the inevitable discovery doctrine (not here in
issue) or a good faith exception to the exclusionary rule.  As for the
latter, the majority held that it would be "inappropriate" for the
state supreme court to adopt a good faith exception in the absence of
action by this Court (82-1711 Pet. App. 7).

   Finally, the majority concluded that Colo. Rev. Stat. Sec. 16-3-308
(Supp. 1982), which renders admissible evidence seized as a result of
a good faith mistake, was inapplicable here, holding that the
statutory exception is limited to errors of fact rather than errors of
law and concluding that the "mistake" in this case had been one of law
in assessing the existence of probable cause to arrest (82-1711 Pet.
App. 8).

   Justice Rovira dissented, both on the question of probable cause to
arrest and on the application of the exclusionary rule (82-1711 Pet.
App. 10-17).

                          SUMMARY OF ARGUMENT

   1. Nothing in the Fourth Amendment or any other provision of the
Constitution either directly or implicitly provides for the exclusion
of illegally seized evidence from criminal trials.  Instead, decisions
of this Court over the last two decades have made it clear that the
exclusionary rule first enunciated in Weeks v. United States, 232 U.S.
383 (1914), and later extended to the states in Mapp v. Ohio, 367 U.S.
643 (1961), is a judicially-created remedy, the paramount and perhaps
sole purpose of which is the deterrence of unlawful police conduct.
See, e.g., United States v. Calandra, 414 U.S. 338, 348 (1974);
Desist v. United States, 394 U.S. 394 U.S. 244, 254 n.24 (1969).  As
the deterrence rationale has achieved supremacy over earlier,
now-discarded justifications for the rule, the Court has recognized
that it makes sense to apply the rule only to those situations in
which its deterrent purpose will in fact be significantly advanced.
Calandra, 414 U.S. at 348.  Accordingly, the Court now employs a
cost-benefit analysis whenever it considers whether the rule should be
applied to particular situations.  When the costs of applying the rule
are found to outweigh whatever deterrent effect it might achieve, the
rule will not be imposed.  See, e.g., United States v. Havens, 446
U.S. 620 (1980);  United States v. Cecolini, 435 U.S. 268 (1978);
Stone v. Powell, 428 U.S. 465 (1976);  United States v. Janis, 428
U.S. 433 (1976);  Calandra, 414 U.S. 338;  Alderman v. United States,
394 U.S. 165 (1969).

   2. After nearly 70 years of experience with the exclusionary rule,
it is now appropriate to apply the same type of cost-benefit analysis
in considering whether to adopt a "reasonable mistake" exception to
the existing rule.  If, as we shall demonstrate in this brief, the
benefits of applying the rule to certain classes of situations are
outweighed by the costs, the Court should not hesitate to reformulate
the rule.  In our submission, a reasoned cost-benefit analysis of the
exclusionary rule compels the conclusion that it should no longer be
applied in those situations in which a reasonably well-trained policy
officer should not have known that the search and seizure in question
violated the Fourth Amendment or in which the violation did not
substantially affect the rights of the subject of the search.
Preliminarily, however, we suggest that this is a situation ill-suited
to a strictly even-handed weighing of costs and benefits.  By
excluding unquestionably relevant evidence, the exclusionary rule
operates in precisely the opposite manner from what we ordinarily
demand of rules of evidence.  Thus, its benefits should not simply be
presumed;  they must, instead, be convincingly demonstrated if they
are to overcome the indisputable costs.  Accordingly, the exclusionary
rule cannot rationally be retained in those circumstances where it is
thought simply that it might produce some benefit.  Similarly, the
rule should not be retained merely because it appears that no better
deterrent to police misconduct currently exists;  the rule must carry
its own weight through demonstrable evidence that it operates in the
manner intended.

   a. The principal benefit claimed for the exclusionary rule is its
deterrent effect.  Unfortunately for the proponents of the rule,
however, it has never been empirically proven that the exclusionary
rules is an effective deterrent in the absolute sense, or even that it
is a relatively more effective deterrent than alternative, less
draconian, Fourth Amendment remedies.  And even if one accepts the
intuitively plausible but unproven assumption that the rule is capable
of deterring police misconduct to some extent, it is readily apparent
as a matter of logic that the deterrent potential of the rule is
drastically reduced, if not wholly eliminated, when it is invoked to
suppress evidence obtained by a reasonably well-trained police officer
unaware that his conduct violated the Fourth Amendment.

   The cases now before the Court demonstrate that in certain
circumstances the rule is both inappropriate and ineffective as a
deterrent device.  In Quintero, the police could not reasonably be
expected to have known that the state supreme court would later hold
that they lacked probable cause to arrest as a burglary suspect a
stranger to the neighborhood found attempting to hide a television set
under his shirt, and unable to produce any identification or
satisfactorily answer routine questions.  On the contrary, many
reasonable people would surely have considered the policy derelict in
their duty had they failed to arrest Quintero on the spot.
Application of the exclusionary rule in this case is thus ineffective,
because of the greatly diminished potential for deterrence when the
policy conduct themselves in a manner they reasonably believe to be
lawful, and inappropriate, because society has little interest in
"deterring" the policy from solving or preventing crime under
circumstances in which the Fourth Amendment violation, if any, could
not reasonably have been predicted.

   Quintero thus demonstrates the need for a "reasonable mistake"
modification to the exclusionary rule in the case of warrantless
searches and seizures.  Shepard and Leon, on the other hand, present
the Court with its first real opportunity to consider whether there is
any justification for application of the exclusionary rule to
situations involving judicial mistakes.  The rule's purpose is to
deter police misconduct, and Leon demonstrates that that purpose
cannot be advanced when law enforcement officers have done exactly
what is demanded of them by obtaining a judicial search warrant and
acting according to its terms.  It is irrational to assume that police
officers can be meaningfully deterred from future "unlawful" conduct
when, at the time of the conduct in question, they had the
authorization of a warrant obtained in the reasonable belief that
there existed probable cause for the search and seizure in question.
As has been often noted, the suppression of evidence that occurs when
a higher court overturns a magistrate's finding of probable cause does
not involve any police misconduct that needs to be deterred;  all that
is involved is disagreement among judges about subtle and
ever-changing principles of law.  There is no rational justification
for applying the exclusionary rule to these situations, which bear not
the slightest relationship to the egregious police misconduct for
which the rule was first devised.

   Finally, the type of error that occurred in Shepard was, in the
circumstances of the particular case, harmless beyond question.  No
doubt there are circumstances in which failure to specify the items to
be seized could lead to serious Fourth Amendment abuses.  But that is
not what happened here.  Instead, it is undisputed that there was
probable cause for the search, that the judge thought he was
authorizing the search that was properly described in the police
application, and that the police conducted the search in exactly the
same manner that they would have if their application had been
attached to or incorporated by reference in the warrant.  Under these
circumstances, the harmless error rule is appropriately invoked to
avoid the draconian consequences of suppression.

   b. The presumed benefits of the exclusionary rule, which are
substantially diluted if not entirely absent in cases like the instant
ones, must be weighed against the rule's undeniable costs.  Those
costs are readily catalogued:

   First, the exclusionary rule excludes from consideration at trial
the very evidence that is most relevant and trustworthy.  The
resulting distortion of the truth-finding process of adversary
adjudication requires justification of the highest order.

   Second, when applied in circumstances in which significant
deterrence of future misconduct is unlikely, the rule benefits only
those who otherwise would be found guilty;  it allows "(t)he criminal
* * * to go free because the constable has blundered." People v.
Defore, 242 N.Y. 13, 21, 150 N.E. 585, 587, cert. denied, 270 U.S. 657
(1926).  The available data demonstrate that the rule, where invoked,
has a substantial effect on the prosecution's ability to obtain
convictions.  Moreover, the effects of the rule are felt most heavily
in drug cases involving defendants who, following dismissal of their
narcotics charges because of the suppression of dispositive evidence,
often go on to commit other crimes, frequently crimes of violence.
The rule affords no remedy, however, for the innocent victims of
unlawful police conduct, who are or should be the very persons most
deserving of protection.

   Third, and irrespective of the actual number of guilty defendants
set free by virtue of the rule, its application necessarily exacts a
high cost in diminished public respect for the judicial system.  The
public perception that there is something wrong with a system of
criminal justice that frees guilty defendants on "technicalities"
cannot lightly be ignored.

   Fourth, and of particular relevance to the instant cases, the rule
lacks the essential ingredient of proportionality when applied to
marginal Fourth Amendment violations.  It utterly fails to take into
account the actual existence of police misconduct that is perceived as
such by the public and that is within the core proscriptions intended
by the Framers of the Fourth Amendment.  Behavior that a reasonably
well-trained officer could not be expected to have known violated the
Fourth Amendment is subject to the same draconian "remedy" as the most
flagrant abuse of police power.

   Fifth, granting for purposes of argument the premise that
application of the rule to conduct close to the often indistinct
boundary between lawful and unlawful searches would meaningfullly
deter some marginally improper police conduct (see United States v.
Johnson, 457 U.S. 537, 560-561 (1982)), in this class of cases the
rule is, almost by definition, as likely to deter proper as improper
conduct.  Thus, one of the gravest costs of relentless application of
the rule to honest police mistakes is not merely that "the criminal *
* * (shall) go free because the constable has blundered," but that the
crime shall go undetected (or, worse, unprevented) because the
exclusionary rule has deterred the officer from the lawful performance
of his duties.

   Sixth, the present rule substantially strains the judicial system
by encouraging the filing of suppression motions irrespective of
whether there is even the slightest evidence of serious police
misconduct.  The windfall benefits of the rule to the guilty defendant
are so overwhelming as to completely negate the process of
self-screening and evaluation on the part of criminal defense counsel.
 A country whose judicial system is as seriously overloaded as ours
can ill-afford the continued application of a rule that fosters such
vast amounts of make-work.

   Finally, the rule actually diminishes the Fourth Amendment by
making judges reluctant to condemn questionable practices because of
the extreme consequences -- total suppression of unquestionably
relevant and frequently dispositive evidence and the release,
unpunished, of a dangerous offender.

   c. While the trilogy of cases now before the Court serves to
demonstrate some of the varying situations in which a "reasonable
mistake" exception to the exclusionary rule would be appropriate, many
of the practical details relating to the operation of such an
exception may be left to future cases and initial development by lower
courts.  For now, it is sufficient to note that the most
commonly-voiced objections to a reasonable mistake exception are
lacking in substance.  For example, it has been claimed that the
proposed exception would "put a premium on police ignorance" because
the incentive for thorough police training in the requirements of the
Fourth Amendment now provided by the exclusionary rule would be lost.
This objection is a palpable strawman.  The reasonableness of a police
officer's actions would be tested by the objective standard of what
should be expected of the reasonably well-trained law enforcement
official.  Thus, a reasonable mistake exception would preserve every
incentive for police departments to ensure that their officers remain
current with the development of Fourth Amendment law.

   Moreover, the objective nature of the inquiry will protect the
judicial system against unduly burdensome and generally irrelevant
inquiries into the subjective state of mind of a particular officer.
In most cases, a court will need to determine only whether a
reasonably well-trained officer should have known, in light of the
extant principles of law, that his conduct was prohibited.  The
inquiry thus will not be markedly different from that required of a
court in deciding a suppression motion.

   It is also sometimes suggested that the exclusionary rule needs to
be retained in its present form, or even expanded, so as not to
"freeze" the development of Fourth Amendment law.  Of course, it is
not entirely clear that society is greatly benefitted by having courts
continue to decide every question that inventive lawyers can devise,
particularly when "the general principles applicable to claims of
Fourth Amendment violations are well settled * * * ." Arkansas v.
Sanders, 442 U.S. 753, 757 (1979).  But, in any event, there need be
no serious concern that adoption of a reasonable mistake exception to
the exclusionary rule would bring a halt to the adjudication of
substantive Fourth Amendment issues.  Many unsettled questions of
Fourth Amendment law are amendable to adjudication in suits for
declaratory or injunctive relief or in damages actions against
municipalities.  In addition, as demonstrated by the number of
nonmeritorious suppression motions currently filed, criminal
defendants can be counted upon to assert every defense available to
them.  Because the substantial windfall of exclusion would remain
available to those defendants who could show demonstrably unreasonable
police conduct, it is unrealistic to assume that defendants with
colorably meritorious claims of Fourth Amendment violations will lose
their incentive to litigate (although we anticipate that there would
be a considerable reduction in the number of frivolous claims).

   There is, moreover, no jurisprudential impediment to a court's
deciding a question of substantive Fourth Amendment law before
determining the applicability in a particular case of a reasonable
mistake exception to the exclusionary rule.  Such a practice would be
entirely consistent with the customary approach of deciding questions
of rights first, and then turning to questions of remedies.  Indeed,
it is a common feature of current jurisprudence, with appellate courts
first considering an appellant's claim of error and then determining
whether the error was harmless.  Accordingly, whether to assume the
existence of a Fourth Amendment violation and decide only the question
of reasonable mistake, or whether to decide the substantive question
first, should be left to judicial discretion.  It might well be
appropriate for courts to decline to adjudicate nonrecurring
fact-bound questions concerning the propriety of a particular search
and seizure of application of a reasonable mistake exception would be
sufficient to dispose of the case.  On the other hand, courts would
remain free to decide significant unsettled questions of law or to
adjudicate particularly problematic or recurring factual situations
that give cause for concern.

   Finally, it has been suggested that, whatever the flaws of the
exclusionary rule, it must be retained because there is no adequate
alternative.  This is, we submit, insufficient justification for a
rule that carries the heavy costs of the exclusionary rule in the
class of cases here considered.  Moreover, the continued existence of
the rule may well operate to deter the development of more efficacious
and less costly alternatives.  Accordingly, the time has come for
recognition by this Court that, in the category of cases here under
consideration, the exclusionary rule is entirely unjustified, if not
actually detrimental to the achievement of the goals of the Fourth
Amendment.

                               ARGUMENT

 I. AS A JUDICIALLY CREATED RULE OF EVIDENCE, THE EXCLUSIONARY RULE
MAY APPROPRIATELY BE MODIFIED IN THE LIGHT OF EXPERIENCE

   This Court first required the exclusion of evidence obtained in
violation of the Fourth Amendment in Weeks v. United States, 232 U.S.
383 (1914), a case involving successive, warrantless searches by
federal agents of an accused's home, which resulted in the seizure of
letters and other personal documents.  Later, in Mapp v. Ohio, 367
U.S. 643 (1961), the Court extended the application of the Fourth
Amendment exclusionary rule to the states in the context of a case
involving a forcible, warrantless entry into a suspect's home that was
followed by an exploratory search through personal papers and effects.
 Since that time, however, the exclusionary rule has been increasingly
criticized as "both conceptually sterile and practically ineffective
in accomplishing its stated objective" of ensuring compliance with the
Fourth Amendment by law enforcement officials.  Bivens v. Six Unknown
Named Agents of Federal Bureau of Narcotics, 403 U.S. 388, 415 (1971)
(Burger, C.J., dissenting).  Accordingly, members of the Court have
repeatedly urged a general reconsideration of the exclusionary rule
and the situations in which it is applied.  Id. at 415-416, 420-421;
see also Illinois v. Gates, No. 81-430 (June 8, 1983), slip op. 9-22
(White, J., concurring);  Robbins v. California, 453 U.S. 420, 437,
443-444 (1981) (Rehnquist, J., dissenting);  California v. Minjares,
443 U.S. 916, 917 (1979) (Rehnquist, J, dissenting from denial of
stay);  United States v. Ceccolini, 435 U.S. 268, 283 (1978) (Burger,
C.J., concurring);  Brewer v. Williams, 430 U.S. 387, 413-414 n.2
(1977) (Powell, J., concurring);  Stone v. Powell, 428 U.S. 465, 496
(1976) (Burger, C.J., concurring);  id. at 537-539 (White, J.,
dissenting);  Schneckloth v. Bustamonte, 412 U.S. 218, 271 (1973)
(Powell, J., concurring);  Coolidge v. New Hampshire, 403 U.S. 443,
490 (1971) (Harlan, J., concurring).

   The instant cases offer appropriate vehicles for such a
reevaluation of the scope of the exclusionary rule.  In Leon, the
record establishes that the police officers obtained a search warrant
after making a detailed submission to a state court judge based on
both a tip and corroborating information obtained during a month-long
investigation of the tip.  Thereafter, the officers executed the
warrant according to its terms.  As was recognized by the district
court and by Judge Kennedy in dissent, the officers "laid a meticulous
trail" (Pet. App. 14a) by conducting their investigation "with care,
diligence, and good faith" (id. at 5a).  Including the issuing judge,
five judges have examined the officers' application for a warrant, and
they have divided three to two on the existence of probable cause.
Under such circumstances, it seems wholly unreasonable to suppose that
the police can be deterred from making a similar "mistake" in the
future.

   In Sheppard, the officers relied on a search warrant that was
without question supported by probable cause.  Granting that the
warrant was defective because it failed to specify the items to be
seized, those items nevertheless were correctly identified in the
police officer's application for the warrant.  Moreover, there is no
question that the issuing judge knew and approved of the precise scope
of the search that the police intended to conduct, or that the search
was in fact so confined.  See 82-963 Pet. App. A10-A16.  Thus, highly
probative evidence was suppressed because exigent circumstances
surrounding issuance of the warrant resulted in the incomplete
adaptation of boilerplate language in a form warrant.  The fundamental
values that the Fourth Amendment protects were in no way compromised,
while society's equally compelling interest in convicting the guilty
was dealt a needless blow.

   In Quintero, police officers responded to a citizen's report of a
possible burglary.  The police found the suspect, a stranger to the
neighborhood, standing at a corner bus stop in his undershirt, having
placed his shirt over a television set.  The suspect had no
identification and told the police that he had paid someone $100 for
the television set.  Later than day, residents of the neighborhood
reported that their house had been burglarized, and they identified
items recovered from the defendant as items that had been taken from
their home.  See 82-1711 Pet. App. 2-5.  The Supreme Court of Colorado
held that the police lacked probable cause to arrest respondent,
although the majority apparently believed that probable cause would
have been present if the police had had in their possession one
additional fact -- actual knowledge that a burglary had been
committed.  In our view, it is readily apparent that many reasonable
persons would consider the police to have been derelict in their duty
had they failed to arrest respondent simply because the victims of the
burglary had not yet discovered what was obvious to the police -- that
a thief had made off with their property.  But even assuming that the
state court correctly determined the probable cause issue, it is
unrealistic to suppose that the court's decision provides a useful
guide to future police conduct.  Cases such as Quintero highlight the
impossibility of reliably providing precise guidance to the officer in
the field confronted with a close probable cause issue;  while an
officer with an encyclopedic memory for the details of vast numbers of
judicial decisions will, should he ever happen upon precisely the same
facts, know that an appellate court has found them lacking, even the
slightest variation in the facts could lead to a different result that
the officer could not be expected to glean from decisions such as that
in this case.  Under such circumstances, the principal "lesson"
learned by the police is that appellate oversight of the factual
determinations that an officer must make in the daily performance of
his duty offers an uncertain and basically unpredictable guide to
future conduct.

   Thus, in each of the cases now before the Court, the officers'
conduct stands on a far different footing from the palpably unlawful
searches at issue in Weeks and Mapp.  The suppression remedy does not
meaningfully protect against the arbitrary invasion of privacy
interests -- the core value safeguarded by the Fourth Amendment --
when, as in the instant cases, law enforcement officers have acted in
the reasonable belief that their conduct complies with constitutional
standards.  Modification of the exclusionary rule to acknowledge this
point is consistent with the fundamental purpose of the rule and the
cases of this Court explicating it.

 A. The Only Viable Justification For The Exclusionary Rule Is Its
Presumed Deterrent Effect On Unlawful Police Conduct

   Nothing in the Fourth Amendment or any other provision of the
Constitution either directly or implicitly provides for the exclusion
of illegally seized evidence from criminal trials.  Although the
plurality opinion in Mapp, 367 U.S. at 649, 651, 655-656, suggested
that an absolute exclusionary rule is constitutionally required, the
Court has never so held.  Nevertheless, because the exclusionary rule
was first conceived in the context of flagrantly unlawful police
conduct and later extended to the states in a case involving even more
abusive practices, it is not surprising that, for many years, the
Court appeared to assume that the Fourth Amendment required an
absolute prohibition against the use of illegally obtained evidence.
As the Court has come to focus more clearly on the true purpose of the
exclusionary rule and the effect it is likely to have in differing
contexts, however, it has recognized that the rule is merely a
judge-made rule of evidence -- constitutionally based but not
specifically constitutionally required -- the contours of which must
be adapted to fit the circumstances.  See, e.g., United States v.
Calandra, 414 U.S. 338, 348 (1974);  Desist v. United States, 394 U.S.
244, 254 n.24 (1969);  see also Stone v. Powell, 428 U.S. at 542
(White, J., dissenting);  Wolf v. Colorado, 338 U.S. 25, 39-40 (1949)
(Black, J., concurring) (rule "is a judicially created rule of
evidence").  /6/

   Accordingly, the exclusionary rule "has never been interpreted to
proscribe the introduction of illegally seized evidence in all
proceedings or against all persons." Stone v. Powell, 428 U.S. at 486.
 Because of the inherent trustworthiness of seized tangible evidence
and the resulting societal costs from its loss through suppression,
application of the exclusionary rule has been carefully "restricted to
those areas where its remedial objectives are thought most
efficaciously served." Calandra, 414 U.S. at 348.  Thus, any
consideration of the extent to which the rule should be modified must
begin with a clear understanding of its purpose.

   Over time, the justifications advanced in support of the
exclusionary rule have varied, but it is now clear that the principal,
and certainly the only logical purpose of the rule is to deter Fourth
Amendment violations by law enforcement officers by removing the
incentive to commit those violations.  See, e.g., Stone v. Powell, 428
U.S. at 486;  United States v. Janis, 428 U.S. 433, 446 (1976).  The
Court summarized the rule's deterrent purpose succinctly in Elkins v.
United States, 364 U.S. 206, 217 (1960):

         The rule is calculated to prevent, not to repair.  Its
      purpose is to deter -- to compel respect for the constitutional
      guaranty in the only effectively available way -- by removing
      the incentive to disregard it.

   The rise to preeminence of the exclusionary rule's deterrent
purpose reflects the abandonment of earlier justifications.
Initially, the rule was justified as a remedy for the violation of an
accused's personal Fourth Amendment right of privacy.  Weeks, 232 U.S.
at 398.  This rationale has since been repeatedly and squarely
rejected by the Court (e.g., Calandra, 414 U.S. at 347;  Linkletter v.
Walker, 381 U.S. 618, 637 (1965)), and with ample reason.  The
exclusionary rule is fundamentally irrational as a remedy for unlawful
invasions of privacy, both because it utterly fails to succor those
most deserving of a remedy -- the innocent victims of unreasonable
searches -- and because, as Judge Friendly has said in an observation
particularly apt in cases like these of marginal illegality, "the
benefit received (exclusion of evidence proving the defendant's guilt)
is wholly disproportionate to the wrong suffered." Friendly, The Bill
of Rights as a Code of Criminal Procedure, 53 Calif. L. Rev. 929, 951
(1965).

   Another early rationale for the exclusionary rule was that it
served to safeguard the purity of the courts' processes by forbidding
the introduction of tainted evidence.  See Elkins, 364 U.S. at
222-223.  But the "imperative of judicial integrity" has not in fact
served as the basis for deciding cases.  Oaks, Studying the
Exclusionary Rule in Search and Seizure, 37 U. Chi. L. Rev. 665, 669
(1970).  The Court has recognized that the strength of this rationale
has been steadily eroded by a series of decisions permitting the
collateral use of unlawfully seized evidence.  See pages 34-38, infra.
 Thus, preserving the courts' distance from tainted evidence has now
been eclipsed by, and indeed subsumed within, the policy of
deterrence:  to the extent that the judicial integrity rationale was
intended to insulate the courts from becoming partners in lawless
government conduct, that function is fully served by the policy of
deterrence.  See Janis, 428 U.S. at 458-459 n.35;  Stone v. Powell,
428 U.S. at 484-485;  United States v. Peltier, 422 U.S. 531, 536-538
(1975).

   But even if the "imperative of judicial integrity" had survived as
an independent justification for the exclusionary rule, it would not
be impugned by the "reasonable mistake" exception that we propose (see
pages 44-45, 47-49, 65-68, infra).  As the Court recognized in
Peltier, 422 U.S. at 537-538, "the 'imperative of judicial integrity'
is * * * not offended if law enforcement officials reasonably believed
in good faith that their conduct was in accordance with the law even
if decisions subsequent to the search or seizure have held that
conduct of the type engaged in by the law enforcement officials is not
permitted by the Constitution." Indeed, we suggest that judicial
integrity is put in greater jeopardy by the rendition of erroneous
verdicts caused by the suppression of dispositive evidence than it is
by the admission of evidence that a reasonably well-trained police
officer could not have been expected to know was being obtained in
violation of the Fourth Amendment.

 B. The Policy Of Deterrence Dictates A Cost-Benefit Approach To The
Application Of The Exclusionary Rule

   Recognition that the policy of deterrence is the only logical
justification for the exclusionary rule has governed the Court's
consideration of a multitude of applications of the rule.  Because
"the exclusion of evidence is not a personal constitutional right but
a remedy," the judiciary "must be sensitive to the costs and benefits
of its' imposition." Gates, slip op. 11-12 (White, J., concurring).
Indeed, this Court has long engaged in a cost-benefit analysis when it
has confronted suggested expansions of the rule or has examined afresh
the propriety of certain applications of the rule.  For example, in
Alderman v. United States, 394 U.S. 165, 174-175 (1969), the Court
ruled that suppression may be sought only by one whose own Fourth
Amendment rights have been violated.  The Court concluded that any
additional benefits that might flow from extending the suppression
remedy to persons not themselves the victims of unlawful searches and
seizures were offset by "the public interest in prosecuting those
accused of crime and having them acquitted or convicted on the basis
of all the evidence which exposes the truth." Id. at 175.  See also
United States v. Salvucci, 448 U.S. 83, 94-95 (1980);  Rawlings v.
Kentucky, 448 U.S. 98, 104-106 (1980);  United States v. Payner, 447
U.S. 727, 731-734 (1980);  Rakas v. Illinois, 439 U.S. 128, 137
(1978).  /7/

   Similarly, the Court's recognition of the permissible use of
unlawfully seized evidence as an impeachment tool rests on the
conclusion that any furthering of the deterrent purpose of the
exclusionary rule would be more than offset by the interference with
the truthfinding function of criminal trials.  See United States v.
Havens, 446 U.S. 620 (1980);  Walder v. United States, 347 U.S. 62
(1954);  see also Oregon v. Hass, 420 U.S. 714 (1975);  Harris v. New
York, 401 U.S. 222 (1971).  In reaching this conclusion, the Court
noted in Havens that any increase in deterrence occasioned "by
forbidding impeachment of the defendant who testifies (is) deemed
insufficient to permit or require that false testimony go
unchallenged, with the resulting impairment of the integrity of the
factfinding goals of the criminal trial" (446 U.S. at 627).

   Likewise, the Court has refused to apply the exclusionary rule when
the initial illegality has become attenuated.  E.g., United States v.
Ceccolini, 435 U.S. at 280.  Again, a cost-benefit analysis controlled
the outcome of the case (ibid.):

         The cost of permanently silencing (a live witness) is too
      great for an evenhanded system of law enforcement to bear in
      order to secure such a speculative and very likely negligible
      deterrent effect.

   The Court also has employed a cost-benefit analysis in determining
whether to apply the exclusionary rule to various types of proceedings
other than the criminal trial itself.  In Calandra, the Court refused
to prohibit the use of illegally seized evidence in grand jury
proceedings.  In reaching this result, the Court stated (414 U.S. at
351-352;  footnote omitted):

         Any incremental deterrent effect which might be achieved by
      extending the rule to grand jury proceedings is uncertain at
      best.  * * * We therefore decline to embrace a view that would
      achieve a speculative and undoubtedly minimal advance in the
      deterrence of police misconduct at the expense of substantially
      impeding the role of the grand jury.

   A like analysis was employed in Stone v. Powell, 428 U.S. at
482-495, where the Court held that the substantial costs to society of
the suppression remedy would outweigh any marginal deterrent effect
that might follow from permitting state prisoners to relitigate search
and seizure claims in federal habeas corpus proceedings.  And in
Janis, 428 U.S. at 454, the Court concluded that "exclusion from
federal civil proceedings of evidence unlawfully seized by a state
criminal enforcement officer has not been shown to have a sufficient
likelihood of deterring the conduct of the state police so that it
outweighs the societal costs imposed by the exclusion."

   Finally, the Court has employed the same balancing analysis when
considering whether Fourth Amendment decisions should be applied
retroactively.  See, e.g., Peltier, 422 U.S. at 538-539;  Williams v.
United States, 401 U.S. 646, 654-655 (1971) (plurality opinion);
Desist v. United States, 394 U.S. at 249-250;  Linkletter v. Walker,
381 U.S. at 636-639.  /8/ In these cases, the Court has recognized
that retroactive application of new Fourth Amendment standards cannot
meaningfully promote the deterrent purpose of the exclusionary rule.

   In short, the Court has steadfastly declined to apply the
exclusionary rule in circumstances in which the degree of incremental
deterrence that suppression might provide is outweighed by the
attendant societal costs.  /9/ This cost-benefit approach is a
necessary corollary to the fact that deterrence is the only logical
justification for the rule.

 II. THE COSTS OF THE EXCLUSIONARY RULE OUTWEIGH ITS BENEFITS WHEN IT
IS APPLIED TO SUPPRESS EVIDENCE OBTAINED IN A SEARCH AND SEIZURE THAT
A REASONABLY WELL-TRAINED OFFICER WOULD NOT HAVE RECOGNIZED AS A
VIOLATION OF THE FOURTH AMENDMENT

   After nearly 70 years of experience with the exclusionary rule, it
is now appropriate for the Court to employ the same type of
cost-benefit analysis utilized in the past in evaluating particular
applications of the rule (see pages 34-38, supra) to a consideration
of the wisdom of its application to reasonable mistakes.
Preliminarily, however, we suggest that this weighing is not properly
performed on scales that are evenly balanced.  By excluding
unquestionably reliable and relevant evidence, the exclusionary rule
operates in precisely the opposite manner from what we generally
demand of other rules of evidence.  See, e.g., C. McCormick, Handbook
of the Law of Evidence Section 72 (E. Cleary ed. 1972).  Thus, the
rules' benefits should not simply be presumed;  the rule's application
to particular classes of cases requires more than an assumption that
it might have the desired deterrent effect.  As the Chief Justice
observed in his concurrence in Stone v. Powell, 428 U.S. at 499-500:

         To vindicate the continued existence of this judge-made rule,
      it is incumbent upon those who seek its retention * * * to
      demonstrate that it serves its declared deterrent purpose and to
      show that the results outweigh the rule's heavy costs to
      rational enforcement of the criminal law.  * * * The burden
      rightly rests upon those who ask society to ignore trustworthy
      evidence of guilt, at the expense of setting obviously guilty
      criminals free to ply their trade.

   Similarly, Justice White stated in his Gates concurrence (slip op.
12):

         (A)ny rule of evidence that denies the jury access to clearly
      probative and reliable evidence must bear a heavy burden of
      justification, and must be carefully limited to the
      circumstances in which it will pay its way by deterring official
      lawlessness.

   See also Wilkey, The Exclusionary Rule:  Costs and Viable
Alternatives, 1 Crim. Just. Ethics 16, 20 (1982).  In any event, as we
shall now demonstrate, such an analysis reveals that the costs of the
rule far outweigh its presumed benefits when applied to police actions
that may in retrospect be deemed illegal but would not have been
recognizable as such to a reasonably well-trained officer.
Accordingly, the Court should have no hesitation in fashioning an
appropriate exception to the rule.

 A. The Presumed Benefits Of The Exclusionary Rule Are Not Realized By
Applying It To Suppress Evidence Obtained In Searches Or Seizures That
Were Not Recognizably Violative Of The Fourth Amendment

   1. The principal benefit claimed for the exclusionary rule is its
deterrent effect.  Unfortunately for the rule's proponents, however,
its deterrent effect has never been proven, either in an absolute
sense or relative to alternative, less costly means of enforcing the
Fourth Amendment.  The Court itself has acknowledged the lack of
reliable empirical evidence to support the deterrent effect of the
exclusionary rule.  In Wolf v. Colorado, 338 U.S. 25, 44 n.5 (1949)
(Murphy, J., dissenting), Justice Murphy argued that his own
"statistical study" of police chiefs supported a broadened application
of the rule.  /10/ Several years later, however, the Court observed
that "(t)here is no reliable evidence known to us that inhabitants of
those states which exclude the (tainted) evidence suffer less from
lawless searches and seizures than those of states that admit it."
Irvine v. California, 347 U.S. 128, 136 (1954).  See also Elkins, 364
U.S. at 218 ("it cannot positively be demonstrated that enforcement of
the criminal law is either more or less effective under either rule").

   Since Mapp, of course, there have been no meaningful comparative
statistics showing the effect the exclusionary rule has had upon
police conduct.  See Janis, 428 U.S. at 452 and n.24.  The Court has
noted twice in recent years that the available empirical studies are
virtually useless.  Stone v. Powell, 428 U.S. at 492 and n.32;  id. at
498-499 (Burger, C.J., concurring);  Janis, 428 U.S. at 449-453.  This
situation is not surprising in view of the manifest difficulty of
designing and implementing an adequately controlled comparative study
that could produce objectively valid results.

   The commentators, like this Court, have concluded that there is no
reliable evidence to support the proposition that the exclusionary
rule operates effectively to deter police misconduct.  The author of
the leading empirical study on the question has concluded (Oaks,
supra, 37 U. Chi, L. Rev. at 755):

         As a device for directly deterring illegal searches and
      seizures by the police, the exclusionary rule is a failure.
      There is no reason to expect the rule to have any direct effect
      on the overwhelming majority of police conduct that is not meant
      to result in prosecutions, and there is hardly any evidence that
      the rule exerts any deterrent effect on the small fraction of
      law enforcement activity that is aimed at prosecution.  What is
      known about the deterrent effect of sanctions suggests that the
      exclusionary rule operates under conditions that are extremely
      unfavorable for deterring the police.  The harshest criticism of
      the rule is that it is ineffective.

   Thus, the rule cannot be realiably shown to fulfill the only
purpose that justifies its implementation.  Nevertheless, we accept as
intuitively plausible (even if not empirically demonstrated) the
premise that suppression of evidence in a criminal trial can to some
extent or in some circumstances deter law enforcement officers from
violations of the Fourth Amendment.  What is pertinent to the present
inquiry is how well, if at all, deterrence can operate in the
"reasonable mistake" context.  It seems apparent that the degree of
deterrence achieved by the exclusionary rule is likely to vary in
relation to two factors:  the extent to which imposition of the
suppression sanction is "painful," and the extent to which the officer
can predict at the time he acts that his action is improper and
therefore likely to lead to imposition of the sanction.  Cases such as
Calandra, Stone v. Powell, Janis, and Havens turn upon the Court's
assessment of the first of these factors;  they reach the result they
do because it appeared unlikely to the Court that police officers
would be encouraged to engage in prohibited conduct by the
availability of the particular uses of unlawfully seized evidence
there permitted.  Thus, any speculative deterrent effect was clearly
outweighed by the evident costs of suppression.

   The present cases call upon the Court to evaluate the second
factor, i.e., whether deterrence will be too slight to justify the
costs of suppression when the conduct in question is of a sort that a
reasonably well-trained officer would not recognize to be unlawful.
In advancing the contention that exclusion of evidence is unjustified
in such circumstances, we do not (and need not) go so far as to
suggest that adoption of a reasonable mistake exception would have no
effect at all on the presumed deterability of Fourth Amendment
violations.  Perhaps it is tenable to suppose that, if police are
responsive to the suppression sanction, then the more sweeping and
stringent the use of the sanction, the more cautious they will be in
cases in which there is any room for doubt about the legality of a
proposed search or seizure, a point the Court made in United States v.
Johnson, 457 U.S. at 560-561.

   But the mere fact that some deterrence may be postulated plainly
cannot control the inquiry here.  If it did, the Court's decisions
imposing the "standing" requirement, for example, would be totally
untenable;  it is, after all, hardly disputable that a rule allowing
any defendant to obtain suppression would be far more likely to deter
than one excluding the fruits of searches that were not recognizably
illegal at the time they were undertaken.  The question, in short,
does not turn merely upon identification of some reasonable
possibility of deterrence, but requires an evaluation of the
substantiality of the anticipated deterrence.  As the Court noted in
Michigan v. Tucker, 417 U.S. 433, 447 (1974):

         The deterrent purpose of the exclusionary rule necessarily
      assumes that the policy have engaged in willful, or at the very
      least negligent, conduct which has deprived the defendant of
      some right.  By refusing to admit evidence gained as a result of
      such conduct, the courts hope to instill in those particular
      investigating officers, or in their future counterparts, a
      greater degree of care toward the rights of an accused.  Where
      the official action was pursued in good faith, however, the
      deterrence rationale loses much of its force.

   Similarly, in Peltier, 422 U.S. at 542, the Court stated:

         If the purpose of the exclusionary rule is to deter unlawful
      police conduct then evidence obtained from a search should be
      suppressed only if it can be said that the law enforcement
      officer had knowledge, or may properly be charged with
      knowledge, that the search was unconstitutional under the Fourth
      Amendment.

   See also Janis, 428 U.S. at 458-459 n.35;  United States v.
Mahoney, No. 82-1452 (5th Cir. Aug. 22, 1983), slip op. 6707 ("(T)
here may be benefit in uniformly applying the exclusionary rule such
that legality is the sole index of exclusion.  Those benefits bear in
our view too great a price").

   2. Experience teaches that Fourth Amendment violations vary greatly
in their gravity and, we submit, in their amenability to deterrence.
At one end of the spectrum, when officers have made Fourth Amendment
intrusions under circumstances "so lacking in indicia of probable
cause as to render official belief in its existence entirely
unreasonable," or engaged in law enforcement activities that
constitute "flagrantly abusive violation(s) of Fourth Amendment
rights," "the deterrent value of the exclusionary rule is most likely
to be effective." Brown v. Illinois, 422 1.S. 590, 610-611 (1975)
(Powell, J., concurring).  /11/ By contrast, when there is merely a
"technical" violation of Fourth Amendment rights occasioned by actions
that a reasonably well-trained police officer would not recognize as
impermissible, "the deterrence rationale of the exclusionary rule does
not obtain," and there is accordingly "no legitimate justification for
depriving the prosecution of reliable and probative evidence." Id. at
611-612.

   In our view, if the exclusionary rule is to function tolerably in
our society, it must take account of these differences.  Thus, we
endorse Justice White's opinion (Stone v. Powell, 428 U.S. at 538
(White, J., dissenting)) that

      the rule should be substantially modified so as to prevent its
      application in those many circumstances where the evidence at
      issue was seized by an officer acting in the good-faith belief
      that his conduct comported with existing law and having
      reasonable grounds for this belief.  These are recurring
      situations;  and recurringly evidence is excluded without any
      realistic expectation that its exclusion will contribute in the
      slightest to the purposes of the rule, even though the trial
      will be seriously affected or the indictment dismissed.

   See also Gates, slip op. 1, 12 (White, J., concurring).

   This type of focused exception responsive to the policies of the
exclusionary rule has been expressly adopted by the Fifth Circuit.
United States v. Williams, 622 F.2d 830 (5th Cir. 1980) (en banc),
cert. denied, 449 U.S. 1127 (1981).  There, a federal agent who had
previously arrested Williams in Ohio for a narcotics violation
encountered her in Georgia.  The agent knew that a condition of
Williams' release on bond pending appeal was that she remain in Ohio.
Accordingly, the agent arrested Williams for violating this condition
and, in ensuing searches incident to the arrest, seized heroin from
Williams' possession.

   Sitting en banc, the Fifth Circuit held unanimously that the
district court should not have suppressed the heroin.  One majority of
the court held that the federal agent had legal authority to arrest
Williams because, by violating the conditions of her bail release, she
had committed the crime of contempt of court in the agent's presence
(622 F.2d at 836-839).  A different, overlapping majority of the court
held that, irrespective of the validity of Williams' arrest, the
heroin should not have been suppressed because the agent had acted in
good faith in arresting and searching Williams, and could not
reasonably be expected to have known that there was serious doubt
concerning his authority to make the arrest.  Because the purpose of
the exclusionary rule is to deter "willful or flagrant actions by
police, not reasonable, good-faith ones" (id. at 840), the court
concluded that it made no sense to suppress evidence in these
circumstances, "unless we somehow wish to deter (police officers) from
acting at all" (id. at 842).  The court noted that its decision was
fully consistent with this Court's cost-benefit approach to the
exclusionary rule (id. at 842-843;  citations omitted;  emphasis
added):

         Any slight deterrent effect of excluding fruits of good-faith
      arrests is even less than the small deterrence from suppressing
      the fruits of illegal police actions that are attenuated in
      effect, that are challenged in habeas corpus petitions on fourth
      amendment grounds, that are used in grand jury deliberations, or
      that are used for impeachment.  Yet the Supreme Court has found
      that the deterrent effect of exclusion in the examples listed
      and others does not justify the societal harm incurred by
      suppressing relevant and incriminating evidence.  The good-faith
      exception that we explicitly recognize today is of a kind with
      these.  /12/

   3. The "reasonable mistake" exception to the exclusionary rule that
we advocate will be appropriate in a variety of factual settings, not
all of which can or should be precisely mapped out at this stage of
the development of the exception.  But the facts in United States v.
Williams and in Quintero well illustrate two situations in which the
exclusionary rule should be modified to accommodate the practical
realities of police work.  In Williams, the officer was required to
make an on-the-spot decision concerning the scope of his arrest
powers, a legal issue that had not been judicially resolved.
Irrespective of what an appellate court might ultimately announce as
the correct answer to that legal question, there can be no doubt that
the officer was not unreasonable in believing that he had observed the
commission of a crime in his presence.  Society expects the police to
act in such situations, and it cannot seriously be urged that society
is benefitted, or that individual constitutional liberties are
meaningfully advanced, by a rule of law that causes an officer to
doubt the propriety of taking action when he observes what he
reasonably believes to be an offense in progress.

   Similarly, in Quintero, the court found that the arresting officer
believed he had probable cause to arrest the respondent (82-1711 Pet.
App. 6);  indeed, it is difficult to imagine that the officer could
have believed anything else.  But regardless of the "correct" answer
to the probable cause issue, /13/ the officer was called upon to make
an immediate judgment involving a mixed question of law and fact as to
which, at minimum, reasonable persons could differ.  Again, society is
not benefitted by a rule of law that seeks to "deter" law enforcement
officers who reasonably believe that a crime has been committed from
performing their duty to make an arrest.

   As the cases now before the Court demonstrate, policemen are not
trained legal technicians;  nevertheless, they are expected to make
quick decisions, often involving complicated legal and factual
analyses, "in the course of the difficult and often dangerous business
of law enforcement." Wright, Must the Criminal Go Free If the
Constable Blunders?, 50 Tex. L. Rev. 736, 741 (1972).  Thus, countless
officers in the field must daily decide under rapidly-changing
circumstances whether there exists the requisite probable cause to
support an arrest or a search, reasonable suspicion to justify an
investigative detention, or exigent circumstances permitting
warrantless action.  In such cases, "(i)nadvertent errors of judgment"
and "honest mistakes" will "inevitably occur given the pressures
inherent in police work having to do with serious crimes." Bivens, 403
U.S. at 418 (Burger, C.J., dissenting).

   The uncertainties inherent in police work are exacerbated by a lack
of coherent Fourth Amendment standards that are readily recognizable
and can be predictably applied by officers in the field.  Too often,
courts leave police officers to resolve these difficult questions for
themselves, see New York v. Belton, 453 U.S. 454, 470 (1981) (Brennan,
J., dissenting), and then feel free to second-guess what appeared at
the time to have been reasonable judgments.  The result is that the
courts have engendered a "state of uncertainty" that is "intolerable"
to the officer on the beat.  Coolidge v. New Hampshire, 403 U.S. at
490-491 (Harlan, J., concurring).  /14/ Without the ability accurately
to predict how courts will resolve Fourth Amendment questions, law
enforcement officers will neither know the scope of their authority
nor be sufficiently deterred from improper action to justify
application of the exclusionary rule.  See New York v. Belton, 453
U.S. at 459-460;  see also LaFave, Improving Police Performance
Through the Exclusionary Rule, 30 Mo. L. Rev. 391, 395 (1965).  /15/

   There is no basis for faulting an officer who has made a reasonable
but incorrect assessment regarding the existence of reasonable
suspicion or probable cause or the necessity of obtaining a warrant.
Fourth Amendment adjudications inevitably leave "much room for
disagreement among judges, each of whom is convinced that both he and
his colleagues are reasonable men.  Surely when this Court divides
five to four on issues of probable cause, it is not tenable to
conclude that the officer was at fault or acted unreasonably in making
the arrest." Stone v. Powell, 428 U.S. at 540 (White, J., dissenting).
 /16/ Justice White went on to note (id. at 539-540):

         (E)xperience tells us that there will be those occasions
      where the trial or appellate court will disagree on the issue of
      probable cause, no matter how reasonable the grounds for arrest
      appeared to the officer and though reasonable men could easily
      differ on the question.  It also happens that after the events
      at issue have occurred, the law may change, dramatically or ever
      so slightly, but in any event sufficiently to require the trial
      judge to hold that there was not probable cause to make the
      arrest and to seize the evidence offered by the prosecution.  *
      * *

         In these situations, and perhaps many others, excluding the
      evidence will not further the ends of the exclusionary rule in
      any appreciable way;  for it is painfully apparent that in each
      of them the officer is acting as a reasonable 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.  /17/

   Quite clearly, it is in these "grey, twilight area(s), where the
law is difficult for courts to apply, let alone for the policeman on
the beat to understand," that the exclusionary rule is least
efficacious in deterring police misconduct.  Schneckloth v.
Bustamonte, 412 U.S. at 269 (Powell, J., concurring).  /18/

   4. The reasonable mistake exception to the exclusionary rule that
we advocate here is consistent with this Court's recognition of the
ameliorating effects of police good faith in other Fourth Amendment
contexts.  /19/ For example, in Michigan v. DeFillippo, 443 U.S. 31
(1979), a police officer made an arrest in good-faith reliance on a
municipal ordinance later declared to be unconstitutional.  In an
ensuing search incident to the arrest, the officer seized drugs from
the defendant's person.  In upholding the admissibility of the seized
drugs, the Court stated (id. at 37-38):

         A prudent officer, in the course of determining whether (the
      defendant) had committed an offense under all the circumstances
      shown by this record, should not have been required to
      anticipate that a court would later hold the ordinance
      unconstitutional.  * * * /20/

   Similarly, in United States v. Caceres, 440 U.S. 741 (1979),
Internal Revenue agents conducted a series of "consensual electronic
surveillance" encounters with a targeted taxpayer.  Although internal
agency guidelines required prior authorization for such surveillance,
the agents failed to obtain written authorization.  Refusing to
require suppression of the fruits of the unauthorized surveillance,
the Court noted that "(t)he agency action, while later found to be in
violation of the regulations, nonetheless reflected a reasonable,
good-faith attempt to comply in a situation" in which monitoring was
appropriate and would have been authorized had the request for
authorization been received more promptly (id. at 757).  So too, in
Hill v. California, 401 U.S. 797 (1971), officers had probable cause
to arrest Hill;  however, the officers mistakenly arrested one Miller,
who was present in Hill's apartment, and conducted a search incident
to the arrest that disclosed evidence incriminating Hill.  In
upholding the validity of the seizure, the Court stated:  "The upshot
was that the officers in good faith believed Miller was Hill and
arrested him.  They were quite wrong as it turned out, and subjective
good-faith belief would not in itself justify either the arrest or the
subsequent search.  But * * * the officers' mistake was understandable
and the arrest a reasonable response to the situation facing them at
the time" (id. at 803-804).  And in Franks v. Delaware, 438 U.S. 154
(1978), the Court limited the circumstances in which a defendant may
challenge the truthfulness of allegations in a search warrant
affidavit to those effectively involving official bad faith.  Thus, as
the Court made clear, "(t)here must be allegations of deliberate
falsehood or of reckless disregard for the truth * * * .  Allegations
of negligence or innocent mistake are insufficient" (id. at 171).

   5. Finally, the reasonable mistake exception to the exclusionary
rule that we propose comports fully with the context in which the rule
was first promulgated and then applied to the states.  It has been
noted that pre-Mapp cases frequently involved "arrogant or brazen
police behavior." Schroeder, Deterring Fourth Amendment Violations:
Alternatives to the Exclusionary Rule, 69 Geo. L.J. 1361, 1414-1415
(1981) (footnote omitted).  As we observed at the outset (see page 27,
supra), both Weeks and Mapp involved warrantless, exploratory searches
through private papers and effects.  So too, many of the early cases
in which the exclusionary rule was first applied involved equally
egregious misconduct.  /21/ In keeping with this historical
perspective, nothing in the modification we propose will prevent
courts from exckuding evidence obtained through intentional or clearly
abusive police misconduct.

   But it makes no sense to apply a rule of suppression that was
conceived in the context of palpably egregious police misconduct to
the multitude of present-day cases in which law enforcement officers
make all reasonable efforts to comply with the Constitution.  Police
resort to the preferred warrant procedure has markedly increased in
the years since Mapp was decided (see 1 W. LaFave, Search and Seizure:
 A Treatise on the Fourth Amendment Section 1.2, at 26 (1978)), law
enforcement officers have to a far greater extent become well-trained
professionals, and the cases now being litigated most often probe the
"grey, twilight area(s)" of Fourth Amendment law, rather than directly
touching the core values of that constitutional protection.  Against
this background, neither the fundamental values of the Fourth
Amendment nor the deterrent purpose of the exclusionary rule are
meaningfully advanced by the suppression of evidence when law
enforcement officers, even though acting without a warrant, reasonably
attempt to navigate the intricate channels of Fourth Amendment law.
Simply put, when law enforcement officers have acted in a manner far
removed from the egregious type of conduct that the exclusionary rule
was first designed to combat, their honest mistakes should not be met
with the severe sanction of suppression.

 B. The Reasons For Applying The Exclusionary Rule Are Most Remote
When Law Enforcement Officers Have Relied On A Judicially-Issued
Search Warrant

   1. As we have demonstrated, the purpose of the exclusionary rule is
to deter unconstitutional actions by the police.  When law enforcement
officers reasonably, albeit mistakenly, believe that they are acting
lawfully, the potential for deterrence is drastically diminished and
the social value of deterrence greatly reduced.  In those
circumstances, the justification for the suppression remedy vanishes.
That is the situation in Quintero.  Equally important, however, is the
fact that no credible justification has ever been advanced for
invoking the exclusionary rule when, as in Leon and Sheppard, the
police have not engaged in any misconduct whatsoever, but a judicial
officer has issued a search warrant that is subsequently held to be
defective.  "This Court has never set forth a rationale for applying
the exclusionary rule to suppress evidence obtained pursuant to a
search warrant;  it has simply done so without considering whether
Fourth Amendment interests are advanced." Gates, slip op. 17 (White,
J., concurring).  The situation is thus remarkably similar to that
presented in Stone v. Powell, in which the Court acknowledged that its
prior decisions had not fully considered the extent to which the
exclusionary rule should apply in federal habeas corpus proceedings
(428 U.S. at 480-481 and n.15).  Upon examination, of course, the
Court concluded that the cost of permitting state prisoners to
relitigate search and seizure issues outweighed any incremental
deterrent effect that might flow from application of the exclusionary
rule in that context.  Here too, the Court is presented with its first
real occasion to examine the policies of the exclusionary rule as they
relate to evidence obtained pursuant to a warrant.  As in Stone v.
Powell, should that examination reveal the absence of sufficient
justification for continuing to apply the exclusionary rule in such
circumstances, the Court should not hesitate to modify the rule.

   2. In our submission, the exclusionary rule is an inherently
inappropriate device for deterring Fourth Amendment violations that
are the result of judicial miscalculation, rather than police
misconduct.  As the Court observed in Janis (428 U.S. at 448),
application of the exclusionary rule must be tied to the identity of
those who are to be deterred and the nature of the conduct that is to
be controlled.  In the Fourth Amendment context, "the exclusionary
rule was adopted to deter unlawful searches by police, not to punish
the errors of magistrates and judges." Gates, slip op. 18 (White, J.,
concurring).  Accordingly, as was recognized by the plurality in
Sheppard (82-963 Pet. App. A47-A49):

         The exclusionary rule may not be well tailored to deterring
      judicial misconduct.  If applied to judicial misconduct, the
      rule would be just as costly as it is when it is applied to
      police misconduct, but it may be ill-fitted to the job-created
      motivations of judges.  As we have said, ideally a judge is
      impartial as to whether a particular piece of evidence is
      admitted or a particular defendant convicted.  Hence, in the
      abstract, suppression of a particular piece of evidence may not
      be as effective a disincentive to a neutral judge as it would be
      to the police.  It may be that a ruling by an appellate court
      that (a) search warrant was unconstitutional would be sufficient
      to deter similar conduct in the future by magistrates.  We
      question, therefore, whether suppression of evidence is
      necessary as a deterrent in cases where the police conduct was
      entirely proper, the defendant was not prejudiced by the
      magistrate's error, and an appellate court clearly identifies
      the magistrate's error of law as a guide to future conduct.

   See also United States v. Acosta, 501 F.2d 1330, 1337 (5th Cir.
1974) (Gee, J., dissenting), modified, 509 F.2d 539 (5th Cir.), cert.
denied, 423 U.S. 891 (1975);  State v. Lien, 265 N.W.2d 833, 840-841
n.1 (Minn. 1978);  State v. Nolting, 312 Minn. 449, 456-457 n.7, 254
N.W.2d 340, 345 n.7 (1977).

   Thus, even if one accepts the premise that the exclusionary rule is
capable of affecting police behavior in some circumstances, there is
no basis whatsoever for assuming that it can have any impact on
magistrates.  Magistrates are not part of the law enforcement "team"
(see Coolidge v. New Hampshire, 403 U.S. 443, 450-453 (1971));  as
neutral judicial officers, magistrates have no stake in the outcome of
any criminal prosecution, and the threat that evidence may be excluded
from trial cannot logically be expected to have a significant
deterrent impact on them.  Instead, judicial officers considering
warrant applications presumably are motivated -- like judicial
officers performing other duties -- to reach a correct decision.  /22/

   3. The suppression of evidence obtained pursuant to
judicially-issued search warrants, even though an unintended extension
of the exclusionary rule as originally conceived, might be justified
if it furthered the rule's basic purpose of deterring police
misconduct.  But in fact it does no such thing.  See Gates, slip op.
17 (White, J., concurring).  Rather, "(i)mposing an admittedly
indirect 'sanction' on the police officer in that instance is nothing
less than sophisticated nonsense" (Stone v. Powell, 428 U.S. at 498
(Burger, C.J., concurring)), because law enforcement officers will
never be deterred from executing a search warrant that a judge has
told them is valid.  "Once the warrant issues, there is literally
nothing more the policeman can do in seeking to comply with the law."
Ibid.  /23/ See United States v. Hill, 500 F.2d 315, 322 (5th Cir.
1974);  Gifford v. State, 630 S.W.2d at 391;  cf. United States v.
Ross, 456 U.S. 798, 823 n.32 (1982) ("(A) warrant issued by a
magistrate normally suffices to establish" that a law enforcement
officer has "acted in good faith in conducting the search");  United
States v. Alvarez-Porras, 643 F.2d 54, 65-66 (2d Cir.), cert. denied,
454 U.S. 839 (1981) (deterrent purpose of exclusionary rule is not
served in circumstances that include the agents' good-faith attempt to
comply with the warrant requirement).  /24/ Quite clearly, neither the
fundamental values of the Fourth Amendment nor the deterrent purpose
of the exclusionary rule can be meaningfully advanced by the
suppression of evidence in cases such as Sheppard, where a search
warrant is invalidated because of a technical defect resulting from
oversight;  /25/ suppressing it because the issuing official, although
authorized by statute to issue warrants, is found to lack the
requisite degree of neutrality, see Coolidge v. New Hampshire, 403
U.S. 443 (1971):  /26/ or suppressing it because, as in Leon, a
reasonable presentation of information to a neutral judicial officer
is later determined to fall short of probable cause, e.g., United
States v. Karathanos, 531 F.2d 26, 35 (2d Cir.), cert. denied, 428
U.S. 910 (1976);  United States v. Travisano, 560 F. Supp. 627,
628-630 and n.2 (D. Conn. 1983), pending on appeal, No. 83-1159 (2d
Cir., filed Apr. 28, 1983).

   4. Application of the exclusionary rule to the fruits of
judicially-warranted searches is not only ineffective in terms of
deterrence, but may well reduce incentives for police resort to the
warrant procedure, which this Court has repeatedly held is the
constitutionally preferred method for safeguarding individual privacy
rights.  See Gates, slip op. 21;  United States v. United States
District Court, 407 U.S. 297, 317 (1972);  Terry v. Ohio, 392 U.S. 1,
20 (1968);  United States v. Ventresca, 380 U.S. 102, 106-107 (1965);
Johnson v. United States, 333 U.S. 10, 14 n.3 (1948);  2 W. LaFave,
Search and Seizure:  A Treatise on the Fourth Amendment Section 4.2,
at 29 (1978).  /27/ Thus, a reasonable mistake exception to the
exclusionary rule when a warrant has been obtained would provide a
substantial incentive for law enforcement officers to utilize the
preferred warrant procedure.  See Brown v. Illinois, 422 U.S. at 611
and n.3 (Powell, J., concurring).  Unlike instances in which the
police have acted without judicial authorization and in which an
exclusionary rule might, in limited circumstances, provide a deterrent
to future misconduct, resort to the warrant procedure itself provides
a substantial alternative barrier to unreasonable or otherwise
defective searches and seizures.  See Jones v. United States, 362 U.S.
257, 270-271 (1960);  Johnson v. United States, 333 U.S. at 14;
United States v. Lefkowitz, 285 U.S. 452, 464 (1932).  For this
reason, the Court has recognized that errors of judgment by a
magistrate should not necessarily be treated as severely as Fourth
Amendment violations by law enforcement officers acting without
judicial supervision and approval.  See Gates, slip op. 21, 24;
United States v. Watson, 423 U.S. 411, 423 (1976);  Spinelli v. United
States, 393 U.S. 410, 419 (1969);  United States v. Ventresca, 380
U.S. at 109;  Aguilar v. Texas, 378 U.S. 101, 111 (1964);  Jones v.
United States 362 U.S. at 270-271.  As the Court explained in Aguilar,
378 U.S. at 111, quoting Jones, 362 U.S. at 271:

         (W)hen a search is based upon a magistrate's, rather than a
      police officer's, determination of probable cause, the reviewing
      courts will accept evidence of a less "judicially competent or
      persuasive character than would have justified an officer in
      acting on his own without a warrant," * * * and will sustain the
      judicial determination so long as "there was substantial basis
      for (the magistrate) to conclude that narcotics were probably
      present . . . "

   A reasonable mistake exception to the exclusionary rule in the case
of evidence seized pursuant to a warrant would thus fully comport with
the special status the Court has attached to warrants in the past.

   5. We do not suggest that the exclusionary rule is never
appropriate when a search has been conducted pursuant to a warrant, or
that the mere issuance of a warrant wholly forecloses further inquiry
into the existence of probable cause.  Even when a warrant has been
obtained, suppression of evidence may be justified if the factors
relied on by the magistrate "were so lacking in indicia of probable
cause as to render official belief in its existence entirely
unreasonable," Brown v. Illinois, 422 U.S. at 610-611 (Powell, J.,
concurring), or if the warrant was procured in bad faith or on the
basis of material misrepresentations, see Franks v. Delaware, 438 U.S.
154 (1978).  See also Gates, slip op. 19 (White, J., concurring).

   For example, in Nathanson v. United States, 290 U.S. 41, 46 (1933),
a search warrant was obtained "upon a mere affirmation of suspicion
and belief without any statement of adequate supporting facts."
Similarly, in Aguilar v. Texas, 378 U.S. at 109 & n.1, the warrant was
based on a "bare-bones" affidavit which, although averring probable
cause, supplied no supporting facts.  While the officers who executed
the search warrants in Nathanson and Aguilar perhaps acted in good
faith, certainly no officer today could reasonably rely on the
validity of similar warrants in light of the unambiguous legal
authority condemning "bare-bones" affidavits.  Application of the
exclusionary rule in such cicrumstances would be consistent with its
historic underpinnings.  But as Professor Amsterdam has written, "the
rule is a needed, but grudgingly taken, medicament;  no more should be
swallowed than is needed to combat the disease." Amsterdam, Search,
Seizure, and Section 2255:  A Comment, 112 U. Pa. L. Rev. 378, 389
(1964).  /28/

   Manifestly, the rare circumstances that might justify exclusion of
the fruits of a judicially-warranted search are not present in the
cases now before the Court.  In Leon, the police took meticulous care
to ensure that their conduct at all times comported with
constitutional requirements.  First, rather than acting precipitously
based on an informant's tip, the police independently investigated the
allegations in the tip through extensive surveillance of respondents
and their various residences.  When their surveillance confirmed the
accuracy of much of the information provided in the tip, the police
did not act on their own initiative, but instead sought a warrant from
a neutral judicial officer.  /29/ Moreover, they provided the judicial
officer with every bit of information they possessed that would assist
him in making a reasoned, independent decision.  And they executed the
warrant properly and with no reason to be on notice that it was not
valid.  In turn, the judge issuing the warrant clearly had at least
"reasonable cause to believe there was reasonable cause." H. Friendly,
Benchmarks 261 (1967).  In these circumstances, it would advance no
Fourth Amendment policy to suppress the seized evidence.

   While the kind of defect present in Sheppard is quite different
from that found by the court of appeals in Leon, there too the Fourth
Amendment would not be well-served by suppression.  Admittedly, the
search warrant was technically defective, and the defect, had it been
noticed, would have been obvious to the issuing judge and to the
officers as well.  Moreover, the defect could have been significant
if, for example, the police had attempted to exploit it by searching
for items, such as drugs, for which they lacked probable cause and
which the judge had not intended to authorize.  But no such abuses
occurred here.  Instead, there is no question that the police had
probable cause to seize the items specified in the warrant
application, it is undisputed that the judge thought he was
authorizing the police to conduct only the search described in the
warrant application, and it is further undisputed that the police did
in fact limit their search to that for which they thought they had
valid authorization.  The failure of the warrant to specify the items
to be seized was, in short, entirely nonprejudicial to Sheppard's
right to be free from unreasonable searches and seizures.  Under these
circumstances, only a policy of attempting to deter even the most
harmless human error could justify invocation of the exclusionary
rule.  /30/ Such a policy would bear not the slightest resemblance to
the policies that led to the exclusionary rule that the Court
fashioned in Weeks and Mapp.  /31/

 C. In Light Of The Exclusionary Rule's Inability To Fulfill Its
Deterrent Purpose When Applied To Reasonable Mistakes, Its Costs Are
Higher Than Our System Of Criminal Justice Can Afford

   Many of the costs of the exclusionary rule have been alluded to in
previous sections of this brief.  Nevertheless, in completing the
cost-benefit analysis that we commend to the Court, it is appropriate
to recapitulate briefly the most obvious costs and to elaborate more
fully on some of the less evident ones.

   First, the exclusionary rule excludes from consideration at trial
the very evidence that is most relevant and trustworthy.  /32/ The
rule thus subverts the courts' paramount truthfinding function.  See,
e.g., Stone v. Powell, 428 U.S. at 489;  id. at 499-500 (Burger, C.J.,
concurring);  Janis, 428 U.S. at 448-449.

   Second, the exclusionary rule directly benefits only those who are
unquestionably guilty.  In the now-famous words of Justice Cardozo,
particularly apt to consideration of a reasonable mistake exception,
the rule allows "(t)he criminal * * * to go free because the constable
has blundered." People v. Defore, 242 N.Y. 13, 21, 150 N.E. 585, 587,
cert. denied, 270 U.S. 657 (1926).  The rule does nothing, however, to
repair injury to innocent victims of unreasonable searches.  While,
judiciously applied, it may prevent future violations of
constitutional rights, that objective can be accomplished by limiting
use of the suppression sanction to cases in which substantial
deterrence of future misconduct can realistically be expected.

   Proponents of the exclusionary rule have argued that only a very
small number of guilty defendants actually go free because of it, and
that this is a small price to pay to safeguard the Fourth Amendment
rights of all citizens.  /33/ In addition to the fact that the freeing
of even one guilty defendant by virtue of an irrational application of
the rule may exact a greater cost than society should be expected to
bear (see pages 71-73, infra), this argument disregards evidence that
tneds to demonstrate very real costs, in numerical terms, of the
rule's operation.

   It is no doubt true, as Justice White observed (Gates, slip op. 12
(White, J., concurring)), that "(w)e will never know how many guilty
defendants go free as a result of the rule's operation," but still
certain conclusions are possible (id. at 12 n.13):

         The effects of the exclusionary rule are often felt before a
      case reaches trial.  A recent study by the National Institute of
      Justice of felony arrests in California during the years
      1976-1979 "found a major impact of the exclusionary rule on
      state prosecutions." National Institute of Justice, The Effects
      of the Exclusionary Rule:  A Study in California 2 (1982).  The
      study found that 4.8% of the more than 4,000 felony cases
      declined for prosecution were rejected because of search and
      seizure problems.  The exclusionary rule was found to have a
      particularly pronounced effect in drug cases;  prosecutors
      rejected approximately 30% of all felony drug arrests because of
      search and seizure problems.  /34/

   Moreover, in cases in which prosecutors elect to proceed to trial
despite successful suppression motions, the resulting conviction rates
are dramatically impaired.  GAO Report, supra note 34, at 13.  /35/
Although the systemic effects of the exclusionary rule have never been
fully calculated, the limited studies available thus demonstrate that
a definite relationship exists between the suppression of evidence and
the prosecution's ability to obtain a conviction.  /36/

   But even if the numerical impact of the exclusionary rule were to
be discounted, the rule exacts an exceedingly high societal cost.
This Court has noted that the exclusionary rule may well serve to
lessen public respect for the judicial system.  "Thus, although the
rule is thought to deter unlawful police activity in part through the
nurturing of respect for Fourth Amendment values, if applied
indiscriminately it may well have the opposite effect of generating
disrespect for the law and administration of justice." Stone v.
Powell, 428 U.S. at 490-491.  Moreover, indiscriminate application of
the exclusionary rule may foster a public perception that the courts
are simply unaware of reality.  See Bivens, 403 U.S. at 415 (Burger,
C.J., dissenting) (deterrence rationale is "hardly more than a wistful
dream").  /37/

   In part, this problem of public perception arises because the
exclusionary rule, as currently applied, lacks the vital ingredient of
proportionality.  /38/ As the Chief Justice observed in his
concurrence in Stone v. Powell, 428 U.S. at 490 (footnote omitted):
"The disparity in particular cases between the error committed by the
police officer and the windfall afforded a guilty defendant by
application of the rule is contrary to the idea of proportionality
that is essential to the concept of justice." /39/ This cost of the
exclusionary rule is particularly evident in cases such as those now
before the Court, in which it cannot seriously be urged that the
police engaged in any misconduct.  See pages 48-49, 66-68, supra.  On
the other hand, there can be little doubt that the suppressed
evidence, if admitted, would conclusively establish the respondents'
guilt.

   The chilling effect on legitimate police activities is another less
visible but equally important cost specifically associated with
suppression of evidence garnered in good faith violations of the
Fourth Amendment.  As the circumstances surrounding a particular
proposed course of action bring it closer to the indistinct line often
separating lawful from unlawful searches or seizures, a relentless
application of the exclusionary rule is increasingly likely to deter
the former rather than the latter, since almost by definition this
class of situations is as likely to involve legal as illegal police
activity.  /40/ "To the extent the rule operates to discourage police
from reasonable and proper investigative actions, it hinders the
solution and even the prevention of crime." Gates, slip op. 12 (White,
J., concurring).  Once application of the rule approaches the point at
which it is as likely to chill legitimate police action as to
discourage marginally improper action, powerful justifications indeed
are needed to justify such results.  /41/

   Still another cost of the exclusionary rule is its failure to
provide any remedy for the innocent victims of unlawful searches and
seizures.  Even for the criminal defendant, the primary effect of the
rule's application -- aiding him to secure an acquittal even though he
is guilty -- does not itself repair the breach of privacy that the
Fourth Amendment protects.  See Calandra, 414 U.S. at 347;  Linkletter
v. Walker, 381 U.S. at 637.  And the exclusionary rule is, of course,
an entirely meaningless "remedy" when the victim of the unlawful
search is never accused of a crime.  See Bivens, 403 U.S. at 410
("(f)or people in Bivens' shoes, it is damages or nothing");  id. at
415-416, 417-418 (Burger, C.J., dissenting).

   A further cost of the exclusionary rule, often paid insufficient
attention, is the burden it places on the judicial system.  One-third
of federal defendants going to trial file Fourth Amendment suppression
motions, and 70% to 90% of these involve formal hearings.  GAO Report,
supra note 34, at 10.  Although most of these motions are denied
(ibid.), the effect on judicial and prosecutorial resources is the
same as if the motions were meritorious.  Significantly, the result of
this diversion of resources from criminal trials to pretrial motions
may have its harshest impact on innocent defendants.  See United
States v. Ross, 655 F.2d at 1205-1206 (Wilkey, J., dissenting):

         To understand how the innocent defendant is victimized by the
      diversion of scarce resources from criminal trials to police
      discipline, it is necessary briefly to consider how our criminal
      justice system now operates in fact, if not in theory.  * * *
      (It) ensures that more due process will be required than the
      system can afford to pay for.  As a result, trials have now been
      priced too high to be held in most circumstances * * * .

         Instead, we have come increasingly to rely on an informal
      system of negotiated settlements in the form of plea bargained
      arrangements between prosecutor and defendant.  The results are
      woeful.  Criminals guilty of grievous offenses routinely are
      permitted to escape with convictions for crimes far less serious
      carrying only wrist-slapping penalties.  Meanwhile innocent
      defendants who might well have been vindicated at trial are
      coerced into settling for a conviction on a lesser charge * * *
      .

         It is against this background that we must measure the
      diversion of energy, talent and dollars from the central task of
      fairly determined the guilt and innocence of defendants into the
      work of adjudicating whether the police have blundered.  * * *
      That function should be performed elsewhere and by others.  The
      exclusionary remedy thus literally buys what little in the way
      of Fourth Amendment protection it affords at the cost of more
      trials for criminal defendants.  Even if the rule did a fair job
      of promoting Fourth Amendment values, this would be at best a
      questionable bargain.  /42/

   Finally, the exclusionary rule in the long run threatens the very
Fourth Amendment values it is intended to safeguard.  "If one were
diabolically to attempt to invent a rule sure slowly to undermine the
substantive reach of the Fourth Amendment, it would be hard to do
better than the exclusionary rule." United States v. Ross, 655 F.2d at
1206 (Wilkey, J., dissenting).  This is because of the obvious
reluctance of judges to condemn questionable practices under the
Fourth Amendment when they know that the result of their decision will
be the freeing of a guilty defendant.  The Court has noted the same
effect in considering the permissibility of a retrial under the Double
Jeopardy Clause (United States v. Tateo, 377 U.S. 463, 466 (1964)
(emphasis added)):

         Corresponding to the right of an accused to be given a fair
      trial is the societal interest in punishing one whose guilt is
      clear after he has obtained such a trial.  It would be a high
      price indeed for society to pay were every accused granted
      immunity from punishment because of any defect sufficient to
      constitute reversible error in the proceedings leading to
      conviction.  From the standpoint of a defendant, it is at least
      doubtful that appellate courts would be as zealous as they now
      are in protecting against the effects of improprieties at the
      trial or pretrial stage if they knew that reversal of a
      conviction would put the accused irrevocably beyond the reach of
      further prosecution.

   Similar concerns operate in the context of the exclusionary rule.
In addition, public support for the values served by the Fourth
Amendment can too easily be undermined by a general perception that
Fourth Amendment jurisprudence is bringing about the seemingly
unjustified release into society of dangerous criminals.  Thus,
extravagant applications of the rule cannot help but threaten the
substantive safeguards of the Fourth Amendment.

 D. The Objections To A Reasonable Mistake Exception To The
Exclusionary Rule Are Insufficient To Overcome The Need For
Modification

   We think it evident that the foregoing cost-benefit analysis of the
exclusionary rule demonstrates the need for a properly designed
reasonable mistake exception to the rule.  Although many of the
practical details concerning the application of such an exception are
best left to future cases and initial resolution by lower courts, cf.
United States v. Williams, 622 F.2d at 847;  United States v. Nolan,
530 F. Supp. at 399, we shall undertake briefly to answer some of the
most commonly-voiced objections to our proposal.

   1. Critics of a reasonable mistake exception to the exclusionary
rule invariably argue that it would "put() a premium on 'police
ignorance.'" /43/ This is a palpable strawman.  As the Fifth Circuit
explained in Williams, 622 F.2d at 841 n.4a, the test for applying the
exception is essentially objective:

         We emphasize that the belief, in addition to being held in
      subjective good faith, must be grounded in an objective
      reasonableness.  It must therefore be based upon articulable
      premises sufficient to cause a reasonable, and reasonably
      trained, officer to believe that he was acting lawfully.  Thus,
      a series of broadcast breakins and searches carried out by a
      constable -- no matter how pure in heart -- who had never heard
      of the fourth amendment could never qualify.  /44/

   See also Gates, slip op. 21 (White, J., concurring);  United States
v. Nolan, 530 F. Supp. at 399;  People v. Adams, 53 N.Y.2d at 9-10,
422 N.E.2d at 541;  Carrington, Good Faith Mistakes and the
Exclusionary Rule, 1 Crim. Just. Ethics 35, 38-39 (1982);  Schroeder,
supra, 69 Geo. L.J. at 1420;  Ball, Good Faith and the Fourth
Amendment:  The "Reasonable" Exception to the Exclusionary Rule, 69 J.
Crim. L. & Criminology 635, 655 (1978);  cf. Scott v. United States,
436 U.S. 128, 137-138 (1978).

   The objective standard we propose ensures that ignorance will not
be rewarded.  On the contrary, "(g)rounding the modification in
objective reasonableness * * * retains the value of the exclusionary
rule as an incentive for the law enforcement profession as a whole to
conduct themselves in accord with the Fourth Amendment." Gates, slip
op. 15-16 n.15 (White, J., concurring).  Because such an objective
standard requires individual officers to have a reasonable knowledge
of what the law prohibits, see United States v. Peltier, 422 U.S. at
542;  United States v. Ajlouny, 629 F.2d at 841;  United States v.
Nolan, 530 F. Supp. at 399, the adoption of a reasonable mistake
exception may actually enhance, but in any event certainly will not
discourage, efforts to educate police officers about the extant
principles of law.  To avoid the risk of suppression through
unreasonable ignorance, /45/ police departments can be expected
(assuming validity in the hypothesis of deterrence by which the rule
is justified in the first place) to ensure that individual officers
are reasonably well trained, especially as the extent to which a
police department takes seriously its duty of providing training and
guidance to officers in the field might be considered in determining
whether the exclusionary rule should be invoked.  See Gates, slip op.
15-16 n.15 (White, J., concurring);  Kaplan, supra, 26 Stan. L. Rev.
at 1050-1051.

   The objective standard we propose is consistent with the standard
applied in civil suits against public officials for alleged
deprivations of constitutional rights.  See Harlow v. Fitzgerald, No.
80-945 (June 24, 1982), slip op. 17:  "government officials performing
discretionary functions generally are shielded from liability for
civil damages insofar as their conduct does not violate clearly
established statutory or constitutional rights of which a reasonable
person would have known." /46/ Importantly, the Court in Harlow
expressly rejected the civil equivalent of the "premium on police
ignorance" argument (id. at 18;  footnotes omitted):

         By defining the limits of qualified immunity essentially in
      objective terms, we provide no license to lawless conduct.  The
      public interest in deterrence of unlawful conduct and in
      compensation of victims remains protected by a test that focuses
      on the objective legal reasonableness of an official's acts.
      Where an official could be expected to know that certain conduct
      would violate statutory or constitutional rights, he should be
      made to hesitate;  and a person who suffers injury caused by
      such conduct may have a cause of action.  But where an
      official's duties legitimately require action in which clearly
      established rights are not implicated, the public interest may
      be better served by action taken "with independence and without
      fear of consequences." Pierson v. Ray, 386 U.S. 547, 554 (1967).

   The same considerations apply with equal force to criminal law
enforcement.

   2. Because the focus of the inquiry will be objective
reasonableness, rather than an officer's subjective intent, the
reasonable mistake exception we propose is not likely to burden the
courts unduly.  Generally, it will be unnecessary for courts to engage
in unwieldy and awkward inquiries into the subjective intent of
arresting or searching officers.  Instead, a reasonable mistake
exception would require only an objective assessment of the officer's
conduct in light of the factual circumstances of a particular case and
the extent to which the governing legal principles had been
predictably articulated.  /47/ It will, therefore, merely require
courts to make determinations of a kind that are not materially
different from those they presently make in ruling upon suppression
motions.  /48/

   3. It is sometimes suggested that the exclusionary rule is needed
to provide Fourth Amendment cases for the courts to adjudicate.  See,
e.g., Goodpaster, An Essay on Ending the Exclusionary Rule, 33
Hastings L.J. 1065, 1074 (1982);  Geller, Enforcing the Fourth
Amendment:  The Exclusionary Rule and its Alternatives, 1975 Wash.
U.L.Q. 621, 654-656;  Oaks, supra, 37 U. Chi. L. Rev. at 756.  "The
risk (in modifying the exclusionary rule) is that our constitutional
rights will atrophy." Geller, supra, 1975 Wash. U.L.Q. at 655
(footnote omitted).

   This presumed risk should be placed in proper perspective.
Assuming, arguendo, that adoption of a reasonable mistake exception to
the exclusionary rule would substantially reduce the incentive for
defendants to litigate substantive Fourth Amendment questions, the
Court should bear in mind that the lost decisionmaking opportunities
will be confined to the "grey, twilight area(s)" of Fourth Amendment
law where the constitutional violation, if any, is minimal.  In these
areas at least, it would seem that our society would reap greater
benefits from a more rational application of the exclusionary rule
than from continued judicial resolution of every Fourth Amendment
question that inventive lawyers can devise.  Just as there is a point
of diminishing returns in the application of the exclusionary rule,
/49/ so too there is a point at which decisions of only marginal
constitutional significance may be overpriced.

   In any event, we are extremely skeptical about the validity of any
assumption that defendants will lose their incentive to litigate
meritorious substantive Fourth Amendment questions if confronted with
a reasonable mistake exception to the exclusionary rule.  The
overwhelming lack of success of most suppression motions (see page 74,
supra) does not seem to have had any effect on the number of such
motions filed.  Practical experience tells us that criminal defendants
commonly assert suppression claims with little regard for their
ultimate chances of success -- in part, no doubt, because of the
magnitude of the benefit to them if "lightning" should strike.  While
adoption of a reasonable mistake exception will tend to discourage
presentation of substantively insubstantial Fourth Amendment
suppression motions, it thus seems highly improbable that litigation
of colorable Fourth Amendment issues will "atrophy" to any significant
degree.

   Although the number of cases may not materially decline, there
would be an important easing of the judicial workload because it would
no longer be necessary for courts to decide very conceivable question
of Fourth Amendment law.  Many of the arguably meritorious Fourth
Amendment claims that courts must now resolve present, like Leon and
Quintero, fact-specific questions the resolution of which, while often
difficult, does little to advance understanding of Fourth Amendment
principles of general importance.  In such instances, it will
generally be far easier to determine the applicability of the
reasonable mistake exception than to grapple with the nettlesome but
relatively inconsequential underlying substantive question.  The
modification we propose should thus result in important advances for
the cause of judicial economy.

   On the other hand, we see no jurisprudential impediment to a
court's undertaking to decide important, recurrent, and unsettled
substantive Fourth Amendment questions even when the reasonable
mistake exception may control the outcome of the particular case.
That is precisely what this Court did in an analogous context in
O'Connor v. Donaldson, 422 U.S. 563 (1975).  We therefore view the
issue of whether to decide the substantive question first or to
dispose of a case strictly on the basis of a reasonable mistake
exception as one best committed to judicial discretion.  In
nonrecurring, fact-bound situations, a court might well conclude that
little purpose is served by unnecessarily adjudicating the Fourth
Amendment question.  On the other hand, significant legal issues or
particularly problematic factual situations of concern to a court
could still be considered.  /50/

   This would be comparable to the approach now employed by this Court
in applying the harmless error doctrine.  In some cases, the Court
exercises its discretion to decide the merits of a claim even though
the error was harmless, while in others it resolves the case solely by
reliance on the harmless error doctrine.  Compare, e.g., Milton v.
Wainwright, 407 U.S. 371, 372 (1972) (Court declines to decide whether
admission of confession was constitutional violation because error, if
any, was harmless beyond a reasonable doubt), with Coleman v. Alabama,
399 U.S. 1 (1970) (Court holds defendants constitutionally entitled to
counsel at preliminary hearing, but remands to state court for
determination whether denial of counsel was harmless error);  /51/ see
also United States v. Blackwell, 694 F.2d 1325, 1340 n.22 (D.C. Cir.
1982) (court explains reasons for deciding constitutional question
before determining there was no "plain error").

   Leaving this matter to judicial discretion in individual cases does
no violence to Article III's case or controversy requirement.  Nothing
in Article III prevents a court from analyzing the issues presented by
a suppression motion in whatever order it deems most appropriate.  The
essence of Article III is that the judicial power be exercised only in
live controversies presenting concrete disputes between adversaries.
See, e.g., Valley Forge Christian College v. Americans United for
Separation of Church and State, Inc., 454 U.S. 464, 471 (1982).  There
can be no doubt that a defendant who claims that he has been subjected
to an unlawful search or seizure and seeks suppression of the
evidentiary fruits thereof raises a live controversy within the
Article III authority of federal courts to adjudicate.  And, as a
matter of logic, it is surely appropriate for a court to decide
whether there has been a wrong before deciding what remedy to impose.
See Gates, slip op. 19 n.18 (White, J., concurring).  /52/

   Finally, as noted by Justice White (Gates, slip op. 20 & n.19
(White, J., concurring)), many important Fourth Amendment issues can
be resolved in other settings, such as actions for declaratory or
injunctive relief brought by persons having a reasonable fear of
future exposure to the challenged practice, or damages actions against
municipalities under 42 U.S.C. 1983.  Accordingly, the fear that
Fourth Amendment law will become "frozen" in its current state seems
groundless.

   4. Finally, both supporters and critics of the exclusionary rule
have expressed reluctance about modifying it in the absence of an
effective alternative.  See, e.g., Bivens, 403 U.S. at 415, 420-421
(Burger, C.J., dissenting);  Goodpaster, supra, 33 Hastings L.J. at
1100;  Geller, supra, 1975 Wash. U.L.Q. at 688.  If the exclusionary
rule were actually capable of deterring reasonable police mistakes,
this concern would have some force.  We have already noted, however,
as has the Court (see pages 40-41, supra), that there is at most an
impressionistic basis for the assumption that the exclusionary rule in
fact deters police misconduct.  More importantly, in many of the cases
to which a reasonable mistake exception would apply, there is no
misconduct to deter.  Under these circumstances, it simply makes no
sense to hold on to a demonstrably costly "remedy" that is incapable
of achieving its stated purpose.  In our submission, the exclusionary
rule must be evaluated on its own merits;  if it fails to accomplish
its objective, it should be appropriately modified, irrespective of
the efficacy of the alternatives that might be substituted.

   In any event, a number of alternatives have been suggested.  See,
e.g., Wilkey, supra, 1 Crim. Just. Ethics at 24-26 (suggests executive
branch disciplinary boards, civil tort remedies, or "mini-trials" for
offending officers following the main criminal trial);  Goodpaster,
supra, 33 Hastings L.J. at 1100-1107 (recommends administrative agency
regulation of police conduct).  Whether any of these alternatives will
be effective cannot be known until they are tested;  what should be
obvious, however, is that the alternatives cannot possibly be any less
effective than the exclusionary rule in its current form for cases
like the ones now before the Court.  Moreover, as has been noted by
others, the continued existence of the exclusionary rule may itself
actually inhibit experimentation with different approaches by the
political branches of government.  See Stone v. Powell, 428 U.S. at
500-501 (Burger, C.J., concurring);  United States v. Ross, 655 F.2d
at 1208 (Wilkey, J., dissenting);  Schroeder, supra, 69 Geo. L.J. at
1385.  Accordingly, we submit that the presence of immediately
available effective alternatives is simply not a controlling
consideration in deciding whether the current rule requires the kind
of modification that we propose.

                              CONCLUSION

   The judgments under review should be reversed.

   Respectfully submitted.

   REX E. LEE

      Solicitor General

   STEPHEN S. TROTT

      Assistant Attorney general

   ANDREW L. FREY

      Deputy Solicitor General

   KATHRYN A. OBERLY

      Assistant to the Solicitor General

   ROBERT J. ERICKSON

      Attorney

   SEPTEMBER 1983

   /1/ The filing of a consolidated brief in these three closely
related cases was authorized by Justice Rehnquist in an order dated
August 29, 1983.  The formal portions of this brief pertain to No.
82-1771, the case to which the United States is a party, and, unless
otherwise indicated, references to the appendix to the petition and to
the joint appendix are to the documents filed in that case.

   /2/ Not all of the evidence was suppressed as to all of the
respondents because the court held that no single respondent had a
legitimate expectation of privacy in all of the places searched (Pet.
App. 10a-13a;  see also page 8 note 4, infra).

   /3/ Investigation showed that the utilities at the Via Magdelena
condominium were listed in Stewart's name, but that there was no
telephone service (J.A. 47).

   /4/ The district court rejected respondents' additional claims that
the description of the items to be seized in the search warrant was
impermissibly overbroad and that the officers had failed to comply
with the California "knock-notice" rule during the execution of the
warrant (Pet. App. 9a-10a).  Moreover, the court held that only
Sanchez and Stewart had a sufficient expectation of privacy to
challenge the search of the Price Drive residence;  that only Leon had
a sufficient expectation of privacy to challenge the search of the
Sunset Canyon residence;  and that only Stewart and Del Castillo had a
sufficient expectation of privacy to challenge the searches of their
respective automobiles (id. at 10a-13a).  No one, in the district
court's view, was entitled to challenge the search of the Via
Magdelena condominium (id. at 11a).

   /5/ Spinelli v. United States, 393 U.S. 410 (1969);  Aguilar v.
Texas, 378 U.S. 108 (1964).

   /6/ As one commentator put it, "the exclusionary rule does not
'look' like a constitutional doctrine.  * * * (It) is merely one
arbitrary point on a continuum between deterrence of illegal police
activity and conviction of guilty persons." Kaplan, The Limits of the
Exclusionary Rule, 26 Stan. L. Rev. 1027, 1030 (1974).

   /7/ These decisions would not be sustainable if the "imperative of
judicial integrity" were a substantial independent basis for the
exclusion of illegally obtained evidence, because the impact on
judicial integrity of such use does not depend in the least upon
whether the particular defendant's rights were infringed in procuring
the tainted evidence.

   /8/ To the extent that United States v. Johnson, 457 U.S. 537
(1982), may be read as a departure from these cases, we suggest that
it reflects only the Court's concern with according fundamental
fairness for persons similarly situated rather than any general
retreat from the balancing analysis that the Court has consistently
employed in the context of the exclusionary rule.

   /9/ Using the same reasoning, lower federal courts have placed
similar limitations on the application of the exclusionary rule.  See,
e.g., Donovan v. Federal Clearing Die Casting Co., 695 F.2d 1020 (7th
Cir. 1982) (exclusionary rule inapplicable to evidence seized by
Occupational Safety and Health Administration pursuant to
subsequently-invalidated search warrant);  Tirado v. Commissioner, 689
F.2d 307 (2d Cir. 1982) (evidence unlawfully seized by federal
narcotics agents admissible in a federal civil tax proceeding;
unlikely that narcotics agents would be deterred by prospect that
illegally seized evidence might be unavailable in a future tax
proceeding);  United States v. Lee, 540 F.2d 1205, 1211 (4th Cir.),
cert. denied, 429 U.S. 894 (1976) (exclusionary rule inapplicable to
sentencing proceedings);  United States v. Schipani, 435 F.2d 26, 28
(2d Cir. 1970), cert. denied, 401 U.S. 983 (1971) (same);  United
States v. Bazzano, No. 81-1936 (3d Cir. June 17, 1983) (en banc)
(exclusionary rule inapplicable at probation revocation hearings);
United States v. Winsett, 518 F.2d 51, 53-55, (9th Cir. 1975) (same);
United States v. Hill, 447 F.2d 817, 818-819 (7th Cir. 1971) (same);
United States ex rel. Sperling v. Fitzpatrick, 426 F.2d 1161,
1163-1164 (2d Cir. 1970) (same).  But see Lopez-Mendoza v. Immigration
and Naturalization Service, 705 F.2d 1059 (9th Cir. 1983) (en banc)
(exclusionary rule applicable in civil deportation proceedings).

   /10/ Justice Murphy's study consisted of 26 replies to a
questionnaire he himself sent to the police chiefs of 38 large cities.
 Only those replies "of any significance" were discussed in the text
of his dissenting opinion (338 U.S. at 44 n.5).  However commendable
Justice Murphy's attempt to gather empirical evidence may have been,
he himself recognized the need for more comprehensive research
(ibid.).

   /11/ "(T)he object of deterrence would be sufficiently achieved if
the police were denied the fruit of activity intentionally or
flagrantly illegal -- where there was no reasonable cause to believe
there was reasonable cause." H. Friendly, Benchmarks 261 (1967)
(footnote omitted).  See also Wright, Must the Criminal Go Free If the
Constable Blunders?, 50 Tex. L. Rev. 736, 744-745 (1972).

   In accord with that sentiment, the ALI's Model Code of
Pre-Arraignment Procedure Section SS 290.2(2) (1975), provides that
"(a) motion to suppress evidence * * * shall be granted only if * * *
the violation upon which it is based was substantial * * * ." In turn,
the substantiality of a violation is to be determined from a
consideration of "all the circumstances" of a case (id. Section SS
290.2(4)), except in those situations where a violation is "gross,
wilful and prejudicial to the accused" or "appears to be part of the
practice of the law enforcement agency" (id. Section SS 290.2(3)).  As
one commentator has stated, "the purpose of the test is to invite
courts to reconsider the need for exclusion where the fourth amendment
violation is relatively minor and is neither willful nor reflective of
agency policy or general indifference to individuals' rights."
Schroeder, Deterring Fourth Amendment Violations:  Alternatives to the
Exclusionary Rule, 69 Geo. L.J. 1361, 1423 (1981) (footnote omitted).

   /12/ The Fifth Circuit has recently applied the Williams rule in
United States v. Mahoney, No. 82-1452 (Aug. 22, 1983).  Other courts
have adopted similar rules.  See United States v. Ajlouny, 629 F.2d
830, 840-841 (2d Cir. 1980), cert. denied, 449 U.S. 1111 (1981) (even
if warrantless national security wiretap was unlawful, suppression not
required where agents acted in good faith and could not be charged
with knowledge that their conduct was improper);  United States v.
Nolan, 530 F. Supp. 386, 396-399 (W.D. Pa. 1981) (suppression not
required for what was, at most, a technical, good faith violation of
the knock-and-announce rule);  United States v. Wilson, 528 F. Supp.
1129, 1132 (S.D. Fla. 1982) (even if arrest effectuated outside of
officers' territorial jurisdiction was not a lawful citizen's arrest,
good faith exception bars suppression of marijuana);  Gifford v.
State, 630 S.W.2d 387, 391 (Tex. Crim. App. 1982) (suppression not
required where officers relied in good faith on a search warrant later
found to be technically defective);  People v. Adams, 53 N.Y.2d 1,
9-10, 422 N.E.2d 537, 541, 439 N.Y.S.2d 877, 881-882 (1981)
(suppression not required where agent relied in reasonable good faith
on purported authority of accused's girlfriend to consent to a search
of his apartment);  cf. cases cited at pages 37-38 note 9, supra.

   A number of legal commentators have joined the Fifth Circuit and
other courts following its lead in noting the absence of any
meaningful deterrent effect when police officers have acted in the
reasonable belief that their conduct was lawful.  See, e.g.,
Carrington, Good Faith Mistakes and the Exclusionary Rule, 1 Crim.
Just. Ethics 35, 37-38 (1982);  Schroeder, Deterring Fourth Amendment
Violations:  Alternatives to the Exclusionary Rule, 69 Geo. L.J. 1361,
1380 (1981);  Ball, Good Faith and the Fourth Amendment:  The
"Reasonable" Exception to the Exclusionary Rule, 69 J. Crim. L. &
Criminology 635, 650 (1978);  Kaplan, The Limits of the Exclusionary
Rule, 26 Stan. L. Rev. 1027, 1044 (1974).

   /13/ In our view, it is clear that the Supreme Court of Colorado
misread Brown v. Texas, 443 U.S. 47 (1979).  In Brown, the Court held
that the police had unlawfully detained Brown "(i)n the absence of any
basis for suspecting (him) of misconduct" (id. at 52).  Brown had
merely refused to identify himself when stopped in an area frequented
by drug traffickers;  the police could articulate no objective facts
suggesting that Brown was himself engaged in drug dealings or in any
other criminal activity (id. at 49, 52).  In Quintero, by contrast,
the arresting officer did articulate (and the state supreme court
recited) the objective factors that led him to conclude that
respondent had committed a burglary (82-1711 Pet. App. 3-7).
Nevertheless, for purposes of this case, we must assume that the state
supreme court correctly determined the probable cause issue.

   /14/ As Justice Frankfurter once remarked, "the course of true law
pertaining to searches and seizures * * * has not -- to put it mildly
-- run smooth." Chapman v. United States, 365 U.S. 610, 618 (1961)
(Frankfurter, J., concurring).  See also Cady v. Dombrowski, 413 U.S.
433, 440 (1973) ("this branch of the law is something less than a
seamless web").  Legal commentators have agreed with these
observations.  See, e.g., Amsterdam, Perspectives on the Fourth
Amendment, 58 Minn. L. Rev. 349 (1974) ("For clarity and consistency,
the law of the fourth amendment is not the Supreme Court's most
successful product");  Kaplan, The Limits of the Exclusionary Rule, 26
Stan. L. Rev. 1027, 1033 (1974) (Fourth Amendment law "is so
complicated and abstruse that the police often honestly and reasonably
cannot determine in advance" how it will be applied);  Goodpaster, An
Essay on Ending the Exclusionary Rule, 33 Hastings L.J. 1065, 1092
(1982) (Fourth Amendment law marked by "sophisticated, complicated,
and confusing decisions").

   /15/ As Professor LaFave has noted, "(t)he threat of evidence
exclusion can have little impact unless decision-making officers have
some basis for determining what conduct will bring about exclusion"
(30 Mo. L. Rev. at 396).

   /16/ And, of course, the instances are legion in which lower courts
have erroneously condemned officers' actions as violative of the
Fourth Amendment.  Indeed, last Term alone this Court reversed seven
lower court decisions that had invalidated searches or seizures on
Fourth Amendment grounds.  Michigan v. Long, No. 82-256 (July 6,
1983);  Illinois v. Andreas, No. 81-1843 (July 5, 1983);  Illinois v.
Lafayette, No. 81-1859 (June 20, 1983);  United States v.
Villamonte-Marquez, No. 81-1350 (June 17, 1983);  Illinois v. Gates,
No. 81-430 (June 8, 1983);  Texas v. Brown, No. 81-419 (Apr. 19,
1983);  United States v. Knotts, No. 81-1802 (Mar. 2, 1983).  See also
New York v. Belton, 453 U.S. 454 (1981);  United States v. Cortez, 449
U.S. 411 (1981);  Colorado v. Bannister, 449 U.S. 1 (1980);  United
States v. Ramsey, 431 U.S. 606 (1977);  United States v.
Martinez-Fuerte, 428 U.S. 543 (1976);  United States v. Watson, 423
U.S. 411 (1976);  Texas v. White, 423 U.S. 67 (1975).  Because courts
are fallible human institutions, occasional mistakes are unavoidable,
especially when the legal issue is close.  What is unfortunate,
however, is that it should frequently happen that lawfully seized
evidence is suppressed.  The rule for which we contend will greatly
diminish that risk.

   /17/ Lower court judges have made the same point.  E.g., Government
of the Virgin Islands v. Rasool, 657 F.2d 582, 595 (3d Cir. 1981)
(Adams, J., concurring):

         (I)t is not realistic to expect the exclusionary rule to
      deter misconduct on the part of police officers.  Often there is
      no misconduct to deter or punish -- the officer has simply acted
      reasonably in a pressured situation and is later told he guessed
      wrong about how Supreme Court precedents might be interpreted to
      apply in fine-line situations.

   In a similar vein is United States v. Ross, 655 F.2d 1159, 1204
(D.C. Cir. 1981) (en banc) (footnote omitted) (Wilkey, J.,
dissenting), rev'd, 456 U.S. 798 (1982):

         (T)oo many prosecutions * * * have gone awry, not as a result
      of intentional police misconduct, and certainly not because of
      any doubt about the guilt of the criminal, but simply because a
      court, with the benefit of time to reflect and of hindsight,
      concludes that an officer acting under pressure in the field,
      maybe under fear for his own life, failed properly to apply the
      often confused and confusing standards of conduct set out by
      courts interpreting the Constitution.

   Judge Wilkey also observed that in cases in which the law is not
settled, courts "would have to impute to (police officers) nearly
supernatural powers to see the future before we could charge (them)
with knowledge that (their) conduct was unconstitutional" (655 F.2d at
1181).

   /18/ If concrete examples of the problem are necessary, one need
only look to the Court's decisions in New York v. Belton, 453 U.S. 454
(1981), and Robbins v. California, 453 U.S. 420 (1981).  The facts of
the cases were remarkably similar.  In both cases, police officers
lawfully stopped a car, smelled burnt marijuana, discovered marijuana
in the passenger compartment of the car, and lawfully arrested the
occupants.  Thereafter, in Robbins, the officer found two packages
wrapped in green opaque paper in the recessed rear compartment of the
car, opened them without a warrant, and found 30 pounds of marijuana.
In Belton, the officer found a jacket in the passenger compartment,
unzipped the pocket without a warrant, and found a quantity of
cocaine.

   When the Court decided these cases, three Justices opined that both
searches were legal;  three Justices opined that they were both
illegal;  and three Justices controlled the ultimate decision that the
search in Robbins was illegal and that in Belton legal.  It may come
as small consolation to the officer who made the search in Robbins
that only a year later the decision was overruled in United States v.
Ross, 456 U.S. 798 (1982).

   /19/ We speak in this brief of a "reasonable mistake" exception to
the exclusionary rule, rather than a "good faith" exception, because,
as discussed later (see pages 78-80, infra), we believe that the test
for invocation of the exception should be objective in nature.  The
"good faith" terminology has the unfortunate consequence of suggesting
that good intentions, even if objectively unsupportable, should be the
touchstone, a proposition we do not advocate.  But the "good faith"
cases already decided by this Court and discussed in this section of
our brief all satisfy the objective standard of reasonableness that we
propose and could have been decided on that basis.

   /20/ The Court recognized (443 U.S. at 38 n.3):

         The purpose of the exclusionary rule is to deter unlawful
      police action.  No conceivable purpose of deterrence would be
      served by suppressing evidence which, at the time it was found
      on the person of the defendant), was the product of a lawful
      arrest and a lawful search.  To deter police from enforcing a
      presumptively valid statute was never remotely in the
      contemplation of even the most zealous advocate of the
      exclusionary rule.

   /21/ See, e.g., Silverthorne Lumber Co. v. United States, 251 U.S.
385, 390-391 (1920) (prosecutor conceded "outrageous" conduct based on
a warrantless documents search conducted "without a shadow of
authority");  Gouled v. United States, 255 U.S. 298 (1921)
(surreptitious document search);  Agnello v. United States, 269 U.S.
20 (1925) (warrantless search of home as incident to an arrest that
occurred blocks away);  GoBart Importing Co. v. United States, 282
U.S. 344 (1931) (warrantless, exploratory search of documents);
United States v. Jeffers, 342 U.S. 48, 52 (1951) (warrantless search
of hotel room conducted "surreptitiously and by means denounced as
criminal").

   /22/ There is no constitutional requirement that an official
issuing a warrant be either a judge or a lawyer, so long as the
official is neutral and capable of assessing probable cause.  See
Shadwick v. City of Tampa, 407 U.S. 345, 348-350 (1972).  In the
federal system, however, magistrates will usually be trained and
experienced lawyers.  Thus, the Federal Magistrates Act of 1968
requires, with limited exceptions, that all magistrates have practiced
law for five years (28 U.S.C. (Supp. V) 631(b)(1)), that they be
selected pursuant to merit selection procedures (28 U.S.C. (Supp. V)
631(b)(2)), and that they attend special training programs (28 U.S.C.
637).  Although neither constitutionally required nor necessary to
give rise to the preference that reviewing courts extend to a
magistrate's determinations, we think these salutary features enhance
the presumption of propriety that applies to a federal magistrate's
probable cause determinations.  These same enhancing considerations
also apply to the warrants in Leon and Sheppard, both of which were
issued by state court judges.

   Moreover, because the exclusionary rule "is a judicially created
remedy designed to safeguard Fourth Amendment rights generally through
its deterrent effect, rather than a personal constitutional right of
the party aggrieved" (Calandra, 414 U.S. at 348), relentless
application of the rule in warrant cases is both unnecessary and
unwise because suitable and efficacious substitute remedies, less
costly to society, are available, at least in the federal system.  A
United States Magistrate, unlike a law enforcement officer, is subject
to the control and direction of the district court and may be removed
by the court for "incompetency, misconduct, neglect of duty, or
physical or mental disability." 28 U.S.C. (Supp. V) 631(i).  If it
appears that a particular magistrate is serving merely as a "rubber
stamp" or has demonstrated an inability to exercise mature judgment, a
remedy is available that is far more direct and effective, and less
costly to the criminal justice system, than the suppression of
evidence in a later proceeding.  Cf. United States v. Hasting, No.
81-1463 (May 23, 1983), slip op. 6-7 & n.5 (deterrence rationale is an
inappropriate basis for applying most severe sanctions when more
narrowly tailored sanctions are available).

   /23/ As Professor Levy has noted (L. Levy, Against the Law:  The
Nixon Court and Criminal Justice 81 (1974)):

         (T)o penalize the police by holding that a magistrate had not
      scrutinized the facts with enough independence is comparable to
      penalizing a prosecutor by holding that the police obtained the
      evidence illegally.  The sanction of the law strikes the wrong
      party when the police have obtained a warrant.

   /24/ See also Schroeder, Deterring Fourth Amendment Violations:
Alternatives to the Exclusionary Rule, 69 Geo L.J. 1361, 1418-1419
(1981):

         A search conducted in accordance with the terms of the
      warrant necessarily involves good faith * * * .  When the police
      have dutifully applied to a judge or a magistrate for a search
      warrant, and have executed the warrant in strict conformity with
      its terms, exclusion of the evidence thus obtained can have no
      possible deterrent effect on future police conduct.

   Accord, P. Johnson, New Approaches to Enforcing the Fourth
Amendment 8-9 (Working Paper Sept. 1978), quoted in 1 W. LaFave,
Search and Seizure:  A Treatise on the Fourth Amendment Section 1.2,
at 3 (Supp. 1982).

   /25/ See also United States v. Shorter, 600 F.2d 585 (6th Cir.
1979).  In that case, suppression was ordered because, despite a clear
demonstration of probable cause, the magistrate failed to administer
an oath to the affiant "immediately" at the beginning of his
telephonic application for a search warrant, as required by Rule
41(c)(2)(D), Fed. R. Crim. P.

   /26/ Concurring in Coolidge, Justice Harlan noted that nothing in
the unlawful conduct in that case touched on "core" Fourth Amendment
values (403 U.S. at 491).  See also Bivens, 403 U.S. at 418-419
(Burger, C.J., dissenting) (even assuming the conduct in Coolidge was
improper, it "was surely insufficient in nature and extent to justify
the drastic result dictated by the suppression doctrine");  Kaplan,
supra, 26 Stan. L. Rev. at 1036 ("the police practices revealed in
Coolidge v. New Hampshire are hardly incompatible with a moral
society;  yet letting the defendant in that case go free perhaps is").

   /27/ In explaining the essence of the Fourth Amendment, the Court
has stated:  "(W)here practical, a governmental search and seizure
should represent both the efforts of the officer to gather evidence of
wrongful acts and the judgment of the magistrate that the collected
evidence is sufficient to justify invasion of a citizen's private
premises or conversation." United States v. United States District
Court, 407 U.S. at 316.

   /28/ In his concurring opinion in Gates, Justice White stated that
he would apply the exclusionary rule "when it is plainly evident that
a magistrate or judge had no business issuing a warrant" (slip op.
19).  To the extent that this approach would focus on the conduct of
the issuing magistrate, it appears to be analytically contrary to the
proposition that the exclusionary rule is meant to deter police, not
judicial, misconduct.  In practice, however the distinction may be of
little significance.  In our view, those situations in which "a
magistrate or judge had no business issuing a warrant" are probably
coextensive with those situations in which "no well-trained officer
could reasonably have thought that a warrant should issue" (ibid.).
Thus, for exclusionary rule purposes, the danger of a hypothetical
"runaway" magistrate can effectively be controlled by focusing on the
objective reasonableness of the conduct of law enforcement officers in
applying for and executing the search warrant.  Of course, as we have
noted above (see page 60 note 22, supra), personal sanctions are
available to punish federal magistrates who are derelict in their
duties.

   /29/ Because the officers' suspicion in this case focused in part
on respondents' various automobiles, the police were not
constitutionally obliged to obtain a warrant for that part of their
proposed search.  See, e.g., Chambers v. Maroney, 399 U.S. 42 (1970).
Their decision to seek prior judicial approval for the search of the
automobiles is indicative of the reasonableness of their conduct.

   /30/ As previously noted (see page 44 note 11, supra), the ALI has
recognized that such a policy is inappropriate, and that striking the
proper balance requires an assessment of the substantiality of the
violation.

   /31/ We recognize that the Court has not heretofore applied the
harmless error rule in considering the applicability of the
exclusionary rule, but the facts in Sheppard quite clearly justify
such an approach.  The harmless error rule has of course long
encompassed constitutional as well as non-constitutional errors (see
Chapman v. California, 386 U.S. 18, 22 (1967)), and there is no reason
why it should not encompass Fourth Amendment violations that do not
result in any impairment of substantial rights of the defendant.

   /32/ As Judge Wilkey has observed, "it is all important that there
is never any question of reliability in exclusionary rule cases
involving material evidence * * * .  An illegal search in no way
reduces the reliability of the evidence." Wilkey, The Exclusionary
Rule:  Why Suppress Valid Evidence?, 62 Judicature 215, 222 (1978)
(emphasis in original).

   /33/ See, e.g., The Exclusionary Rule Bills:  Hearings on S. 101,
S. 751 and S. 1995 Before the Subcomm. on Criminal Law of the Senate
Comm. on the Judiciary, 97th Cong., 1st Sess. 35-37 (1981) (testimony
of Stephen H. Sachs);  1 W. LaFave, Search and Seizure Section 1.2
n.9, at 1 (Supp. 1982).

   /34/ A 1979 study by the General Accounting Office concluded that
of all cases declined for prosecution by United States Attorneys,
Fourth Amendment search and seizure problems were the primary reason
for declination in only 0.4% of the total.  Comp. Gen. Rep. No.
GGD-79-45, Impact of the Exclusionary Rule on Federal Criminal
Prosecutions 14 (1979) (hereinafter cited as GAO Report).  Federal
declinations may be low, however, because relatively few federal cases
involve manifestly illegal searches.  Assistant United States
Attorneys may thus choose to go forward in a significantly number of
cases that have search and seizure problems that may be assessed as
troublesome but worth litigating.  This hypothesis is borne out by the
frequency with which suppression motions are denied (GAO Report,
supra, at 10).  Moreover, it was later determined that "(m)ost of the
federal caseload at the time the (GAO) study was conducted was
composed of such white collar crimes as embezzlement, fraud and
forgery.  Search and seizure issues are seldom raised in these cases."
National Institute of Justice, The Effects of the Exclusionary Rule:
A Study in California 7 (1982) (hereinafter cited as NIJ Report).

   /35/ According to the GAO study, a conviction was obtained in more
than 84% of the cases in which a suppression motion had been denied.
The conviction rate dropped dramatically, however, to about 50%,
whenever a suppression motion had been granted in whole or in part.
GAO Report, supra note 34, at 13.

   /36/ The deleterious effects of the exclusionary rule on law
enforcement are exacerbated by its tendency in practice to free the
recidivist.  As the NIJ study noted (NIJ Report, supra note 34, at 2):

         For most defendants, the arrest that ended in release because
      of the exclusionary rule was only a single incident in a longer
      criminal career.

                      * * *

         To a substantial degree, individuals released because of
      search and seizure problems were those with serious criminal
      records who appeared to continue to be involved in crime after
      their release.  The felony rearrests included many drug crimes,
      but the majority were for crimes against persons or property, or
      for other felony offenses.

   /37/ It may be significant in this regard that "no other civilized
country has adopted our mandatory rule of the exclusion of probative
material evidence because of police misconduct." Wilkey, supra, 1
Crim. Just. Ethics at 23.  Moreover, the decision of other countries
not to adopt an exclusionary rule has generally come after careful and
deliberate study.  See, e.g., id. at 23-24 & 26-27 nn. 26-35.

   /38/ Prompted by the belief "that any remedy for the violation of a
constitutional right should be proportional to the magnitude of the
violation," the Attorney General's Task Force on Violent Crime has
recommended the adoption of a reasonable good-faith exception to the
exclusionary rule.  Attorney General's Task Force on Violent Crime,
Final Report 55-56 (1981).

   /39/ Judge Wilkey has made the same point, perhaps more
graphically, dissenting in United States v. Ross (655 F.2d at 1208),
in language that foreshadows the Sheppard case:

         (The) penalty (of the exclusionary rule) is administered with
      a sense of proportionality reminiscent of those medieval penal
      systems that prescribed capital punishment for everything from
      pickpocketing on up.  The rule falls mercilessly on evidence
      deemed to have been seized unconstitutionally, without regard
      for the gravity of the police misconduct or the seriousness of
      the crime of which the defendant has been charged.  Even if the
      policeman's actions were only marginally in violation of the
      Constitution despite his good faith while the criminal is guilty
      of rape and murder, still the evidence stays out.  Such a
      disproportion would be regarded as barbaric if used to deter
      crime;  ironically, employed to deter the police many apparently
      consider it "progressive."

   /40/ In addition, these are the very cases in which it is most
likely that courts would erroneously conclude that the Fourth
Amendment has been violated, with the unhappy result of suppressing
lawfully obtained evidence.  See page 51 note 16, supra.

   /41/ The Court has recognized the same point in holding that public
officials enjoy at least qualified immunity in civil damages actions
brought under 42 U.S.C. 1983.  In Scheuer v. Rhodes, 416 U.S. 232, 242
(1974), the Court observed:

         Implicit in the idea that officials have some immunity --
      absolute or qualified -- for their acts, is a recognition that
      they may err.  The concept of immunity assumes this and goes on
      to assume that it is better to risk some error and possible
      injury from such error than not to decide or act at all.

   /42/ The workload generated by the exclusionary rule does not, of
course, cease at the trial court level.  For example, Judge Wilkey has
pointed out that, over a three-year period, 22.1% of the published
opinions of the United States Court of Appeals for the District of
Columbia Circuit in criminal cases involved suppression issues.
Wilkey, Enforcing the Fourth Amendment by Alternatives to the
Exclusionary Rule, 95 F.R.D. 211, 220 (1982).  Similarly, a
substantial portion of this Court's criminal docket regularly involves
Fourth Amendment search and seizures issues.  See page 51 note 16,
supra.  This expenditure of judicial resources on suppression issues
continues unabated even though "the general principles applicable to
claims of Fourth Amendment violations are well settled * * * ."
Arkansas v. Sanders, 442 U.S. 753, 757 (1979).  The most plausible
explanation for this phenomenon, of course, is that the windfall
benefits of the exclusionary rule for guilty defendants are so great
that they effectively negate the likelihood of meaningful
self-screening.

   /43/ See, e.g., Sachs, The Exclusionary Rule:  A Prosecutor's
Defense, 1 Crim. Just. Ethics 28, 32 (1982).

   /44/ The Fifth Circuit's good-faith exception thus entails a
subjective component.  See also United States v. Mahoney, slip op.
6704-6705.  For the reasons discussed below, however, it is our
submission that the subjective inquiry will almost always be
unnecessary and inappropriate.

   /45/ See, e.g., United States v. Downing, 665 F.2d 404, 408 n.2
(1st Cir. 1981) (no occasion to apply a good faith exception because
the necessary predicate of objectively reasonable police conduct not
satisfied);  Holloman v. Commonwealth, 221 Va. 947, 950, 275 S.E.2d
620, 622 (1981) (accord).

   /46/ As the Court explained (Harlow, slip op. 17-18):

         If the law at that time (of the official's action) was not
      clearly established, an official could not reasonably be
      expected to anticipate subsequent legal developments, nor could
      he fairly be said to "know" that the law forbade conduct not
      previously identified as unlawful.

   /47/ Furthermore, it seems unlikely that there will be many
occasions on which a reasonable officer would not have known that his
action was improper, but the particular officer did entertain such a
belief;  the inclusion of a subjective component will therefore rarely
alter the result, but would instead merely produce burdensome and
largely unproductive litigation.  See Harlow, slip op. 18.  It is
possible, however, to imagine cases in which the objective
reasonableness of a belief in the legality of particular conduct could
be overcome by a showing that, for example, the victim of the search
was singled out for harassment.  In such strictly limited
circumstances, a subjective inquiry might be appropriate.  Plainly, no
such circumstances are present in the cases now before the Court.

   /48/ Even if additional burdens were imposed, Judge Friendly has
suggested that they would be preferable to the current system (H.
Friendly, Benchmarks, supra, at 262;  footnotes omitted):

         It is no sufficient objection that such a rule would require
      courts to make still another determination;  rather, the
      recognition of a penumbral zone where mistake will not call for
      the drastic remedy of exclusion would relieve them of
      exceedingly difficult decisions whether an officer overstepped
      the sometimes almost imperceptible line between a valid arrest
      or search and an invalid one.  Even if there were an added
      burden, most judges would prefer to discharge it than have to
      perform the distasteful duty of allowing a dangerous criminal to
      go free because of a slight and unintentional miscalculation by
      the police.

   /49/ Amsterdam, Search, Seizure, and Section 2255:  A Comment, 112
U. Pa. L. Rev. 378, 389 (1964).

   /50/ United States v. Ajlouny, 629 F.2d at 841-842, offers a good
example of a court's sound exercise of discretion in declining to
decide the legality of a search in light of the applicability of a
good-faith exception.  The legal question involved warrantless
national security wiretaps.  Subsequent to the surveillance of
Ajlouny, the Foreign Intelligence Surveillance Act of 1978, 50 U.S.C.
(Supp. V) 1801-1811, became effective.  That Act, by requiring prior
court approval for nearly all foreign intelligence surveillance,
"substantially reduced the importance of deciding in this case whether
the Constitution independently requires the obtaining of a warrant for
foreign intelligence electronic surveillance" (629 F.2d at 842).
Accordingly, the court disposed of the case by relying on the
good-faith exception.  See also United States v. Mahoney, slip op.
6705 n.5 (merits of Fourth Amendment issue neither briefed nor argued
and therefore court declines to decide the issue).

   /51/ The courts of appeals routinely exercise similar discretion in
applying the harmless error doctrine.  Compare, e.g., United States v.
West, 670 F.2d 675, 684-687 (7th Cir.), cert. denied, 457 U.S. 1124
(1982);  United States v. Bulman, 667 F.2d 1374, 1382-1384 (11th Cir.
1982);  Harryman v. Estelle, 616 F.2d 870, 878 (5th Cir. 1980) (en
banc);  United States v. Rosales-Lopez, 617 F.2d 1349, 1355-1356 (9th
Cir. 1980), aff'd, 451 U.S. 182 (1981), with e.g., United States v.
McCulley, 673 F.2d 346, 352 (11th Cir. 1982);  United States v.
Civella, 666 F.2d 1122, 1130 (8th Cir. 1981);  United States v.
Torres, 659 F.2d 1012, 1013 (9th Cir. 1981), cert. denied, 455 U.S.
926 (1982).

   /52/ In Gates, Justice White also suggested that the benefits of a
new Fourth Amendment ruling might be extended to the party in whose
case the rule is first announced (slip op. 21 n.19, citing Stovall v.
Denno, 388 U.S. 293, 301 (1967)).  This aspect of Stovall, however,
has been roundly criticized.  See Beytagh, Ten Years of
Non-Retroactivity:  A Critique and a Proposal, 61 Va. L. Rev. 1557,
1615 (1975) (footnote omitted):

         Stated bluntly, the "chance beneficiary" notion, developed in
      Stovall and relied on in Desist (v. United States, 394 U.S. 244
      (1969)) and other cases, is not and never was required by
      article III.  Cases in which a new rule is adopted but applied
      in a wholly prospective fashion are nonetheless decided on the
      merits.  Although with a prospective holding the result in the
      law-changing case turns on the old rule, not the new one, that
      fact does not remove the case from the category of an article
      III case or controversy.  If it did, the Court would have acted
      improperly (indeed, unconstitutionally) in England (v. Louisiana
      State Board of Medical Examiners, 375 U.S. 411 (1964)), Cipriano
      (v. City of Houma, 395 U.S. 701 (1969)), and the other cases
      adopting new rules for purely prospective application.