                Environmental Protection Agency Overflights
                      and Fourth Amendment Searches

R o u tin e o v e rflig h ts o f in d u strial p lan ts by th e E n v iro n m e n ta l P ro te c tio n A g e n c y (E P A ),
   c o n d u c te d a t law ful altitu d es an d em p lo y in g co m m ercially av ailab le visual aids, d o not
   co n stitu te se a rc h e s u n d e r th e F o u rth A m en d m en t.

C o n sid erin g th e c o m p re h e n siv e n a tu re o f th e fed eral e n v iro n m en tal re g u la to ry schem e,
   c o rp o ra te businesses m ay h a v e no leg itim ate ex p ectatio n o f p riv acy against E P A
   o b se rv a tio n s fo r th e p u rp o se o f d e te c tin g em issions in to th e a ir o r d isc h arg es into
   w ater.

                                                                                           September 23, 1980

                           M EM ORANDUM OPINION FOR
                        TH E D EPUTY ATTORNEY G EN ER A L

   This responds to your request for our views on the question whether
the Environmental Protection Agency’s (EPA ’s) routine overflights of
possible sources of pollution constitute searches under the Fourth
Amendment. This question is addressed in a draft memorandum pre­
pared by the EPA and submitted to the Land and Natural Resources
Division of the Department of Justice. The EPA memorandum states
that routine overflights of possible sources of unlawful pollution are an
important part of its overall enforcement program. Aerial observations
are used to detect discharges into water, emissions into the air (espe­
cially at night), and hazardous waste disposal sites among other things.
Flights are typically made at altitudes meeting FAA regulations, and
observations are made with equipment that includes infrared cameras
(to detect heat differentials caused by underground discharges into
water) and an instrument called the “Enviro-Pod,” which is essentially
equivalent to a high-quality single lens reflex 35mm camera with good
lenses. Such cameras, as well as the thermal infrared scanner, are
commercially available.
   The EPA memorandum concludes that the overflights do not consti­
tute searches as long as they occur at lawful and reasonable altitudes
and use equipment no more sophisticated than commercially available
equipment and as long as the observed facility has not taken measures



                                                          784
to shield itself from overhead observation.1 For the reasons that follow,
our analysis agrees that the EPA memorandum is substantially correct.

                                                   I.

  The governing standard for whether an observation constitutes a
search under the Fourth Amendment was established in K atz v. United
States, 389 U.S. 347 (1967), in which the Supreme Court rejected the
requirement that a physical intrusion occur before a search could be
found and held that attaching an electronic listening device to the
outside of a public telephone booth constituted a search.
          What a person knowingly exposes to the public, even in
          his own home or office, is not a subject of Fourth
          Amendment protection. . . . But what he seeks to pre­
          serve as private, even in an area accessible to the public,
          may be constitutionally protected.
Id. at 351-52. A governmental observation of an individual constitutes a
search whenever it “violate[s] the privacy upon which he justifiably
relie[s].” Id. at 353. As explained by Justice Harlan, this rule contains
“a twofold requirement, first that a person have exhibited an actual
(subjective) expectation of privacy and, second, that the expectation be
one that society is prepared to recognize as ‘reasonable.’” Id. at 361
(Harlan, J., concurring).
   In United States v. Chadwick, 433 U.S. 1 (1977), the Supreme Court
characterized the Fourth Amendment as protecting people “from un­
reasonable government intrusions into their legitimate expectations of
privacy.” Id. at 7. In Rakas v. Illinois, 439 U.S. 128 (1978), the Court
read Katz as holding that
         capacity to claim the protection of the Fourth Amend­
         ment depends not upon a property right in the invaded
         place but upon whether the person who claims the pro­
         tection of the Amendment has a legitimate expectation of
         privacy in the invaded place.
Id. at 143. The Court explained in a footnote that
         a “legitimate” expectation of privacy by definition means
         more than a subjective expectation of not being discov­
         ered. . . . Legitimation of expectations of privacy by law
         must have a source outside of the Fourth Amendment,
         either by reference to concepts of real or personal prop­

    1 A m em orandum from (he D ru g E nforcem ent A dm inistration (D E A ) coneurs in these conclusions.
T he D E A m em orandum actually goes farth er than the E P A in its conclusions, cursorily arguing that
even attem pts to shield objects o r activity from aerial view w ould not create a reasonable expectation
o f privacy that w ould make aerial observation o f those objects o r activities that w ere in fact
unconcealed a search for F o u rth A m endm ent purposes.


                                                 785
          erty law or to understandings that are recognized and
          permitted by society.
Id. at 143-44 n.12. Because flights at lawful altitudes do not invade a
landowner’s property (see United States v. Causby, 328 U.S. 256 (1946);
49 U.S.C. §1508 (1976)), the inquiry regarding EPA overflights is
whether societal understandings recognize a legitimate expectation of
privacy against aerial viewing of a commercial facility for the purpose
of detecting unlawful pollution.

                                                   H.

   As both the EPA memorandum, and the DEA memorandum men­
tioned in note 2 supra, point out, there are no federal cases on the
question of whether an aerial observation can constitute a search for
Fourth Amendment purposes. Two Supreme Court decisions, however,
are especially relevant to the EPA overflight search question.
   In G.M. Leasing Corp. v. United States, 429 U.S. 338 (1977), the
Supreme Court unanimously held that corporations are protected by
the Fourth Amendment. (The Court had farlier held that Fourth
Amendment guarantees apply to businesses as possible subjects of regu­
latory searches. Camara v. Municipal Court, 387 U.S. 523 (1967); See v.
City o f Seattle, 387 U.S. 541 (1967).) The decision recognized that “a
business, by its special nature and voluntary existence, may open itself
to intrusions that would not be permissible in a purely private context.”
429 U.S. at 353. The Court has yet to elaborate the contours of
corporations’ reduced protection.2
   Because the governmental action challenged in G.M. Leasing was a
physical entry, the Court did not address the question of what consti­
tutes a search. Rather, it held that the intrusions, acknowledged to be
searches for constitutional purposes, were not reasonable, distinguishing
 United States v. Biswell, 406 U.S. 311 (1972) (warrantless search of
locked storeroom of a federally licensed gun seller, pursuant to inspec­
tion procedure authorized by Gun Control Act of 1968, held constitu­
tional). The Court decided that where the intrusion was undertaken to
enforce the tax laws against the corporation and “was not based on the
nature of its business, its license, or any regulation of its activities,” the
corporation had Fourth Amendment rights identical to those of an
individual. 429 U.S. at 354. In accordance with Marshall v. Barlow's,
436 U.S. 307 (1978) and Biswell, supra, these elements may serve to
justify warrantless EPA overflights as reasonable, given the specific

  2 T h e E P A m em orandum refers to Clinton Community Hospital Corp. v. Southern Maryland Medical
Center. 374 F. Supp. 450, 456 (D . Md. 1974), in w hich (he c o u rt asserted that corporations have no
right to privacy under the F o u rth A m endm ent. A s the m em orandum points out, the c ourt relied on
United States v. Morton Salt C a . 338 U.S. 632 (1950); but that case was decided long before the
Suprem e C o u rt first expressly rejected (in G.M. Leasing) the position that corporations have no F ourth
A m endm ent privacy protection.


                                                   786
enforcement needs in environmental regulation, even if they are held to
constitute searches.3 More important for the question whether the
flights are searches, these elements may be looked to in defining the
legitimate expectations of privacy of the corporation’s activities. Con­
sidered in the context of the detailed environmental regulatory scheme,
corporate businesses—especially those operating industrial facilities—
may have no legitimate expectation of privacy against EPA observa­
tions for the purpose of detecting emissions into the air or discharges
into water. It might easily be found that emissions into the air and
discharges into water visible from public locales are “knowingly
expose[d] to the public.” Katz, 389 U.S. at 351.
   In Air Pollution Variance Board v. Western Alfalfa Corp., 416 U.S. 861
(1974), the second Supreme Court case of special relevance to the EPA
overflight search question—decided before G.M. Leasing—the Supreme
Court unanimously held that the respondent corporation had not been
the subject of a search when, in daylight, a state health department
inspector entered the outdoor premises of the corporation’s plant and
observed the plant’s smoke stacks in order to check for pollution.
Having neither entered the plant or offices, nor inspected the stacks,
the official “had sighted what anyone in the city who was near the
plant could see in the sky—plumes of smoke.” Id. at 865. The Court
reaffirmed the rule of Hester v. United States, 265 U.S. 57 (1924), that
Fourth Amendment rights do not extend to “sights seen in ‘the open
field.’ ” Because the public could enter the premises on which the
inspector stood, the observation fell within the “open fields” exception
to the Fourth Amendment.
   This case is significant because it unanimously held there to be no
search when (1) from an “open field,” which the public could routinely
enter, officials observed (2) publicly visible emissions from (3) a corpo­
ration’s plant (4) in order to detect pollution. If aerial observation from
lawful altitudes is constitutionally equivalent to observation from the
open fields—and the Court’s emphasis on the observer’s distance from
the plant, on the fact that the public was not excluded from the
observer’s position, and on the analogy to taking noise readings while
standing on a railroad right-of-way suggests that it is—then EPA
overflights would be exempt from Fourth Amendment requirements
under the open fields exception.-4 This case presents a strong precedent,
which any corporation arguing that overflights of its plants are searches
would have to overcome.5 Nevertheless, each case must be considered

   3 T his mem orandum does not consider the issue w h eth er a w arrantless overflight, if held to be a
search, w ould be constitutional.
   4 L ow er court precedent suggests that the use o f view ing equipm ent that is not o f extrem e
technological sophistication w ould not change this conclusion. See discussion infra.
   9    It is w orth noting that the U nited States, as amicus curiae in the case, subm itted a b rie f that
presented exactly the argum ents that the decision advances. It is also w orth noting that on rem and, the
C olorado co u rts held that due process did not require notice prio r to inspection but did require notice



                                                  787
on all its facts to determine whether in the particular circumstances, a
legitimate expectation of privacy has been invaded.6

                                                  III.

   Because whether a legitimate expectation of privacy has been in­
vaded depends on the full set of circumstances, it is useful to describe
the several state court aerial observation decisions before attempting to
catalogue the relevant factors for answering the Fourth Amendment
question. Generalization is especially difficult with these cases.
   In People v. Sneed, 32 Cal. App. 3d 535, 108 Cal. Rptr. 146 (Ct. App.
 1973), a police helicopter hovered at 20-25 feet over defendant’s corral
near the back of his house on his ranch. Several marijuana plants
growing in the corral were spotted; though they were hidden from
public view, they may have been visible from the neighbor’s farm. The
court found there to be a search, saying that in considering the totality
of circumstances, it must look to the location of the premises (urban or
isolated), the natural or artificial barriers to public observation, the
location of public walkways or roads, and the type of governmental
authority. Relying on the rule of Harris v. United States, 390 U.S. 234,
236 (1968), that a non-search observation requires the officials lawfully
to be at their vantage point, the court noted that the helicopter altitude
was unlawful and that there was no evidence of regular flights (by
police, by cropdusters, by mosquito-abatement officials, for example)
over defendant’s ranch. Defendant’s privacy had therefore been in­
vaded.
   In Dean v. Superior Court, 35 Cal. App. 3d 112, 10 Cal. Rptr. 585
(Ct. App. 1973), defendant had cultivated marijuana on a 3/4-acre plot
protected from public view by the surrounding hills and forest. Using
binoculars, police flew as low as 300 feet over the plot. The court
found that no search had occurred. It reasoned that altitude is a minor
factor in determining legitimate expectations of privacy; instead, one
must look to “mankind’s common habits in the use of domestic and
business property.” 35 Cal. App. 3d at 117. Here, any expectation of
privacy was “not consistent with the common habits of mankind in the
use of agricultural and woodland areas.” Id. at 118.
   In People v. Superior Court, 37 Cal. App. 3d 836, 112 Cal. Rptr. 764
(Ct. App. 1974), police, while conducting a routine air patrol at ap­
proximately 500 feet above ground, and first using the naked eye, then

very soon afterw ard , al least w hen the inspections w ere to be used in a hearing before the A ir
Pollution V ariance Board. Air Pollution Variance Board v. Western Alfalfa Corp., 553 P.2d 811 (Colo. S.
Ct. 1976).
   6    T h o u g h the Air Pollution Variance Board opinion does not cite Katz, the issues presented in the
tw o cases w ere the same, namely, an observation constituted a search for F o u rth A m endm ent
purposes. Because the C ourt has read this question as an inquiry into legitim ate expectations of
privacy, the open Helds do ctrin e should be understood as holding that there are no legitimate
expectations o f p rivacy against view ing from an open field, o r indeed, from anyw here the observer has
a right to be.


                                                 788
20-power gyrostabilized binoculars, spotted large, “conspicuous and
readily identifiable” automobile parts in the backyard of a residence. 37
Cal. App. 3d at 839. In these circumstances, no search had occurred.
   In Plunkett v. City o f Lakewood, 2 Civ. 49610 (unreported decision
filed 15 November 1977, Cal. Ct. App., 2d Dist.) cert, denied, 436 U.S.
945 (1978), city officials’ helicopter overflight of plaintiff’s property,
and taking of photographs from that vantage point, was held not to
constitute a search. The available reports of the facts reveal no further
details.
   In State v. Stachler, 570 P.2d 1323 (Haw. S. Ct. 1977), no search was
found where police flew over defendant’s woods-surrounded marijuana
during routine helicopter surveillance and using binoculars from about
300 feet, spotted the marijuana growing in the open field. The court
relied on the open field exception approved in Air Pollution Variance
Board, noting that the police were flying at a lawful and reasonable
altitude. The court observed, however, that a violation of legitimate
expectations of privacy might be found if the overflight were unreason­
ably or unlawfully low, or if surveillance were intensive or amounted
to harassment, or if “highly sophisticated viewing devices” were em­
ployed. Id. at 1328. Here, occasional overflights by cropdusters, com­
mercial planes, and helicopters made any expectation of privacy in the
open field unreasonable.
   In State v. Brighter, 589 P.2d 527 (Haw. S. Ct. 1979), helicopter
observation from 200-250 feet resulting in the spotting of a stolen
automobile van was held not to constitute a search. The court said:
“No reasonable expectation of privacy can be asserted with respect to
an object or activity which is open and visible to the public when the
presence of members of the public may reasonably be anticipated.” Id.
at 530.
   In Burkholder v. Superior Court, 96 Cal. App. 3d 421, 158 Cal. Rptr.
86 (Ct. App. 1979), police, flying in a plane at 1500-2000 feet and using
7 X 50mm binoculars and a camera with a 135mm telephoto lens,
discovered a marijuana patch fairly well-hidden in the woods. Relying
on the Dean agricultural-use test, and distinguishing Sneed on the
ground that that case involved a “purposeful and intensive (helicopter)
overflight at an unreasonable and unlawful altitude (20 feet) during a
random search for contraband” (96 Cal. App. 3d at 426), the court held
that no search had occurred. The optical aids were permissible, said the
court, because the patch could be seen without the aids, albeit in less
detail.
   Finally, in People v. Lashmett, 389 N.E.2d 888 (111. App. Ct. 1979),
police, acting on a tip, flew at 2400 feet over defendant’s farm and
spotted allegedly stolen large farm equipment. In this first Illinois over­
flight case, the court found that no search had occurred.
                                   789
                                    IV.

   The cases suggest that in determining whether a legitimate expecta­
tion of privacy has been invaded by aerial observation, a court would
look to several factors: the altitude of the observer, the type of location
viewed, the nature of the objects or activities observed, the extent to
which the area observed was concealed, the equipment used for obser­
vation, and the frequency of flights over the observed area. In no case
is a finding as to any one of these elements conclusive, although an
extension of the open fields exception to the public airways would
render altitude a conclusive test.
   Altitude. Only the Sneed case, in which the helicopter hovered di­
rectly over the observed property at 20-25 feet and caused a very noisy
disturbance, held an aerial observation to be a search. The other cases
reached the opposite conclusion; in all of them, the flights were at
lawful and reasonable altitudes ranging from 200-2400 feet. EPA
overflights occur at lawful altitudes, but altitude is not determinative of
the reasonableness of privacy expectations. Dean; Stachler.
   In our view, because of the difficulty of protecting against aerial
observation, it is unlikely that a court would adopt the general rule that
observations from public airspace, like those from a public road, fall
within the open field exception. Without such a blanket exception, the
other elements noted by courts will continue to inform decisions about
the legitimacy of privacy expectations.
   Type o f Location. The relevance of the type of location viewed was
explained by a federal court in a case involving FBI agents peering
through a gap in boards covering a garage window facing a public
alley. In United States v. Vilhotti, 323 F. Supp. 425 (S.D.N.Y. 1971), the
court said:
       [A]n agent is permitted the same license to intrude as a
       reasonably respectful citizen would take. Therefore, the
       nature of the premises inspected—e.g., whether residential,
       commercial, inhabited, or abandoned—is decisive; it deter­
       mines the extent- of social inhibition on natural curiosity
       and, inversely, the degree of care required to insure
       privacy.
Id. at 431. Although “decisive” is in our opinion too strong a character­
ization, the nature of the premises is critical to the legitimacy of
privacy expectations. A residence or its backyard (Sneed) is socially
understood to give greater protection against outside intrusion than is a
farm or business (Dean; Lashmett). Looking into a building is far more
likely to be held a search than is observing objects or activities on the
outside. See United States v. Kim, 415 F. Supp. 1252 (D. Haw. 1976)
(telescope looking into apartment a search; observing balcony may not
be search). As indicated by the Supreme Court in G.M. Leasing, busi-
                                   790
 nesses receive less protection from the Fourth Amendment than do
 private residences. An industrial facility whose exterior is viewed from
 overhead by the EPA can claim little legitimate expectation of privacy
 consistent with “mankind’s common habits in the use of . . . business
 property.” Dean, 35 Cal. App. 3d at 117.
    Nature o f Objects or Activities Observed. Although the nature of the
 premises is an important measure of the extent of social inhibition on
 public curiosity, the kind of objects or activities being observed also
 determines in part the legitimacy of privacy expectations. In particular,
 if the objects or activities are large or conspicuous, any expectation of
 privacy with respect to those objects or activities is less reasonable.
 People v. Superior Court; Lashmett. Because material discharged into
 water or emitted into the air is publicly visible, an expectation of
 privacy with respect to these discharges and emissions would be of
 doubtful legitimacy.
    Concealment. The extent to which the observed area is concealed,
either by natural barriers such as hills, woods, grass, or crops or by
 artificial barriers such as a fence, is an important factor in determining
 the reasonableness of any expectations of privacy. Under the Katz
principle that observation of what a person knowingly exposes to the
public does not constitute a search, leaving objects or activities visible
to public walkways (Sneed) or to public roads (Stachler) or to any place
where “the presence of members of the public. may reasonably be
anticipated” (Brighter, 589 P.2d at 530) evidences an absence of reason­
able expectations of privacy. Conversely, efforts to conceal make ex­
pectations of privacy more reasonable. See State v. Kender, 588 P.2d
447 (S. Ct. Haw. 1979) (small marijuana plants hidden among tall grass
in yard surrounded by fence; observation from top of fence using
telescope constitutes search).
    What remains unclear is whether expectations of privacy are reason­
able when efforts to conceal extend only to landbound observers, not to
overflights. The list of considerations advanced by the Sneed court is
directed far more at concealment from landbound observers; moreover,
the Dean court said that the horizontal extension of an activity is a
better measure of its privacy protection than is the altitude of the
overhead plane. None of the cases involve efforts to conceal from
overhead observation. The EPA memorandum and the DEA memoran­
dum regard concealment from land observation as insufficient to create
a reasonable expectation of privacy against overhead inspection.
LaFave, by contrast, argues that such concealment should be sufficient.
1 LaFave, Search and Seizure § 2.3, at 328-30 (1978). The holdings of
the cases summarized above, however, lead us to the conclusion that
the significance of efforts to conceal from landbound observers depends
on the nature of the premises, the type of objects or activities observed,
and the other factors discussed here. We conclude that an industrial
                                   791
 facility should have little expectation of privacy from overhead obser­
 vation of the exterior of its plant or of the land surrounding it, even if a
 fence surrounds the facility to keep intruders out. By contrast, sur­
 rounding the backyard of a residence with a fence should be sufficient
 to raise legitimate expectations of privacy against prying overhead
observation (i.e., from low altitudes). This judgment rests,.as the cases
 direct, on the general social understanding about the nature of the
 objects or activities that can reasonably be expected to be shielded
 when located on particular kinds of premises. Concealment must there­
 fore be considered only one of the factors relevant to determining the
legitimacy of expectations of privacy.
   Observation Equipment. The use of some visual aids does not auto­
matically transform into a search what would otherwise not be a
search. For example, binoculars were approved in Burkholder, Dean,
People v. Superior Court, and Stachler. Moreover, use of a camera does
not transform a non-search into a search. See, e.g., Plunkett, Burkholder,
 United States v. McMillon, 350 F. Supp. 593 (D.D.C. 1972). Burkholder
even approved the use of a telephoto lens on the camera. In addition,
Stachler warned that a search might be held to have occurred if techno­
logically sophisticated equipment were used. It is our conclusion that
no reasonable expectations of privacy are defeated by the use of com­
mercially available visual aids that do no more that provide greater
detail than the naked eye can make out on unconcealed objects or
activities.7
   In addition, if an observation would not constitute a search if carried
out in daylight, using artificial illumination to observe in the dark
would not render it a search. See United States v. Lee, 274 U.S. 559
(1927) (use of searchlight to observe boat at night not a search), cited in
Katz v. United States, supra (supporting proposition that what a person
knowingly exposes to the public gains no Fourth Amendment protec­
tion). If darkness does not generate a legitimate expectation of privacy
against artificial illumination, it should not shield objects or activities
against observation with the aid of “see-in-the-dark” equipment. See
Commonwealth v. Williams, 396 A.2d 1286 (Pa. Super. Ct. 1978) (use of
see-in-the-dark “startron” does not constitute search). Therefore, night­
time overhead observation of the unconcealed exterior of suspected
sources of pollution, using infrared equipment to detect emitted heat or
otherwise to observe without illumination, or using binoculars and

   7    O n facts similar to those in United States v. Kim, supra, a federal court recently found a search in
the use o f a “ high-pow ered telescope (i.e., a M onolux #4352 telescope w ith a 22mm viewer)*' to
observe the inside o f an apartm ent. United States v. Taborda, 491 F. Supp. 50, 51 (E .D .N .Y .). Both
cases involve an invasion o f residential privacy, though som e language in Taborda suggests that the
cou rt envisions a general rule that use o f visual aids constitutes a search. In light o f such cases as
United States v. Grimes, 426 F.2d 706 (5th Cir. 1970) (binoculared observation o f street activity not a
search), this reading o f Taborda w ould be too broad.

                                                  792
 cameras with commercially available lenses, should not constitute a
 search.
    The use of infrared equipment to detect underground discharges—
 which might be considered concealed from ordinary public observa­
 tion—is more questionable. Use of magnetometers, x-rays, radiographic
scanners, or scintillators to perceive concealed objects constitutes a
search. See, e.g., United States v. Epperson, 454 F.2d 769 (4th Cir. 1972)
 (magnetometer use is search). Nevertheless, the decisions on this aspect
of search law—indeed all the federal decisions relevant to the signifi­
cance of visual aids—all concern the invasion of bodily privacy (as
 with the magnetometer at airports) or residential privacy (Kim;
Kender). It is therefore difficult to predict the extent of privacy protec­
tion that surrounds underground discharges.
    Visual aids have generally been approved as sense-enhancement de­
vices; when an instrument is used to detect what to the observer’s
senses is undetectable, a search is likely to have occurred. See United
States v. Bronstein, 521 F.2d 459, 465 (2d Cir. 1975) (Mansfield, J.,
concurring). The technology used by the EPA in its searches should be
evaluated in light of this standard, but it is only one factor in determin­
ing the range of legitimate privacy expectations, which are defined as
well by the nature of the premises, of the objects being observed, and
the like. In this context, we conclude, detection of heat differentials in
unconcealed pools of water should violate no legitimate expectations of
privacy. Indeed, it is likely that, faced with the issue, courts would
recognize the scientific sophistication of industrial businesses and de­
cline to draw a line between use of the human senses and use of devices
able to perceive signals other than light, sound, etc., within the human
range. This would represent a sensible extension of the approval of see-
in-the-dark devices. As briefly described in the EPA memorandum,
therefore, use of the overflight detection equipment, in observing those
facilities technologically sophisticated enough to understand what sig­
nals (e.g., light, heat) are being emitted for possible perception, should
not constitute a search.
   Frequency o f Overhead Flights. Not surprisingly, the legitimacy of
expectations of privacy against overhead flights depends on the fre­
quency of such flights. See Sneed, People v. Superior Court, Stachler,
Burkholder. Routine flyovers by commercial aircraft or by police planes
or helicopters render unreasonable any expectations of privacy with
respect to objects or activities left open for viewing by these potential
observers. Thus, the more routine the EPA flights, and the greater the
air traffic above any observed plant, the less likely is the finding of a
search.



                                   793
                                   V.

   Under the Katz test, all the circumstances of an observation must be
considered before deciding whether it constitutes a search. It is our
conclusion that routine EPA overflights of industrial plants, conducted
at lawful altitudes and employing commercially available visual aids to
detect unconcealed discharges into water or air by observing the exteri­
ors of buildings and open lands, do not constitute searches under the
Fourth Amendment. In these circumstances, the state court decisions,
the few relevant federal court decisions, and especially Air Pollution
Variance Board indicate that expectations of privacy are not reasonable.
Varying any of these circumstances, as the analysis above suggests,
might require a different result.

                                        L arry A. H am m ond
                                Deputy Assistant Attorney General
                                    Office o f Legal Counsel




                                 794
