Based on the readings from a thermal imager, along with, other circumstantial evidence, federal law enforcement officers obtained a warrant to search the premises of Rohn Martin Ishmael and his wife, Debra K. Ishmael. The officers executed the warrant and discovered some firearms and 770 marijuana plants. After being indicted, the Ish-maels moved to suppress the evidence on the ground that the warrantless use of the thermal imager was a constitutionally proscribed search. The district court granted the Ish-maels’ motion to suppress. We now reverse.
I.
The warrant in this case was based upon the following information: In the late summer of -1992, a confidential source informed Paul Black, a Drug Enforcement Administration (“DEA”) officer, that he/she had delivered numerous truck loads of concrete re-mix to the Ishmaels’ secluded, rural property in Nacogdoches .County, Texas. The- Ishmaels, according to the source, took inordinate measures to conceal the need for the concrete. Rohn Ishmael, for example, would manually mix the concrete near the source’s truck and then drive the concrete to another location on the property. His suspicions aroused, Black entered the property and saw two mobile homes and a trailer. Black, however, did not witness any illegal activity.
In August 1993, Black resumed his investigation. He and three other officers returned to the property and followed a roughly built road from the front of the property to a steep embankment where a large hole had been made. They observed around 60 empty bags of cement, a dump truck and a concrete re-mixer parked near the hole. The next day, Black investigated Rohn Ishmael’s criminal record and found at least four separate marijuana-related incidents dating back to 1974, several of which involved the cultivation of marijuana. Black, along with other DEA officers, then surveyed the Ishmaels’ property by air. They observed a mobile home and a-large steel building, separated by about 200 to 300 yards. The steel building stood next to a 2-acre pond. Black entered the property :on foot two more times. .He discovered that the Ishmaels had built a' structure beneath the steel building. The substructure was wired for electricity and was being fed water from the nearby pond by way of exposed rubber tubes and a water pump. The substructure also had an exhaust fan, which Black noticed was continuously running. Black also observed a nearby pallet containing 100 5-gallon plastic buckets.
Suspecting that the Ishmaels were cultivating marijuana in the structure beneath the steel building, the DEA boarded a helicopter with a thermal imager and flew over the Ishmaels’ property at approximately 500 to 1000 feet.. A thermal imager detects differences in surface temperature of targeted objects and displays' those differences through a viewfinder in varying shades of white and gray. In other words, a warm object will appear white on the device’s viewfinder, whereas a cool object will appear *852 gray. The device can record its readings on a standard videocassette. The DEA’s recording of the Ishmaels’ property showed that, although the water entering the substructure was noticeably cool, the water exiting it was emitting a substantial amount of heat. The recording additionally showed that the ground adjacent to the substructure was much warmer than the ground further from the substructure.
Black then subpoenaed the Ishmaels’ telephone records. The records indicated that the Ishmaels had made numerous calls to various horticulture shops, two of which appeared on a narcotics intelligence computer base as suppliers for other marijuana cultivators. Black also subpoenaed the Ishmaels’ electrical utility records. The records showed that the substructure’s-power usage was extremely high and far exceeded the mobile home’s power usage.
In September 1993, Black and several other officers again entered the Ishmaels’ property on foot. Using a hand-held- thermal imager, the officers canvassed the perimeter of the steel building-but never entered it. The officers made essentially the same findings; an unusual amount of heat was emanating from the • substructure and the ground adjacent to it. ' Black displayed his recordings to two DEA- thermographers, both of whom concluded that the Ishmaels were illegally cultivating marijuana in the steel building’s substructure. The DEA then used the thermal imager’s readings, along with the wealth of information gathered by Black, to obtain a warrant to search the steel building and its substructure on the Ishmaels’ property. The officers executed the warrant two days later and uncovered 770 marijuana plánts and several firearms. After being indicted in October 1993, the Ishmaels moved to suppress the evidence obtained pursuant to the search warrant. They argued that the readings from the thermal imager constituted an unconstitutional search and that, without those readings, the DEA did not have probable cause to obtain a warrant.
The district court granted the motion to suppress in January 1994.
See United States v. Ishmael,
According to the district court, the burden then shifted to the government to prove that its search fell within one of the several recognized exceptions to the warrant requirement. The government, relying on
Dow Chemical Company v. United States,
*853 Having found that the use of the thermal imager constituted a search proscribed by the Fourth Amendment, the court proceeded to determine whether the remaining evidence amounted to probable cause. The court noted that the DEA had no direct evidence of illegal activity taking place on the Ishmaels’ property. Id. at 213-14. The court stated, “The evidence of their activity was consistent with developing a new patented strain of African violets, and innumerable other perfectly legal activities.” Id. at 214. On this basis, the court concluded that a judge would not find that probable cause existed for issuing a warrant, and it therefore granted the Ishmaels’ motion to suppress. The government now appeals the district court’s holdings that the warrantless use of the thermal imager was unconstitutional and that, absent its readings, probable cause did not exist for the issuance of the warrant.
II.
A.
In reviewing a district court’s ruling on a motion to suppress, we review the court’s conclusions of law de novo and its findings of fact for clear error.
United States v. Cardenas,
B.
The warrantless use of thermal imagers by the police has spawned a fair amount of search and seizure jurisprudence over 'the last several years.
1
Though the Fifth Circuit has yet to squarely address this issue,
2
three of our sister circuits have, and each has concluded that such use is not a “search” proscribed by the Fourth Amendment.
United States v. Myers,
1.
The Fourth Amendment provides in part: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated.” U.S. Const, amend. IV. As in any Fourth Amendment surveillance case, our analysis begins with
Katz v. United States,
In cases involving very similar facts, other courts have readily accepted the heat waste analogy in concluding that the defendants’ have failed to satisfy
Katz
’ first prong.
See, e.g., Myers,
Thus, unless we intend-to render
Katz’
first prong meaningless, we must conclude that the Ishmaels exhibited a subjective expectation that their hydroponic laboratory would remain private.
See Smith v. Maryland,
2.
We now must address whether the government’s intrusion on the Ishmaels’ subjective expectation of privacy with a thermal imager is a reasonable one.
Oliver v. United States,
Dow Chemical
provides useful guidance for search and seizure cases involving surveillance technology. There, the Environmental Protection Agency, without a warrant, had flown over Dow’s industrial plant with a precise mapping camera. Dow argued that the use of the camera was an unconstitutional search. The Supreme Court disagreed, reasoning that the government is not foreclosed from using technology to enhance its surveillances,
provided
that that technology does not reveal “intimate details.”
Id.
at 238,
A thermal imager, according to the government, is no more intrusive than the other animate and inanimate means of surveillance that the Supreme Court has concluded does
*856
not offend the Fourth Amendment. That, is, like the trained canine in
Place
or the precise mapping camera in
Dow Chemical,
a thermal imager is an acceptable surveillance technique because it does not reveal intimate details within the structure being scanned. Instead, the government argues, the device assesses only heat differentials in objects and therefore poses no threat to the privacy concerns that the Fourth Amendment is intended to protect. The Ishmaels contend, however, that a thermal imager is the functional equivalent of an X-ray machine in that it allows officers to “see” within a structure what it otherwise cannot see with the naked eye. Specifically, they argue, a thermal im-ager measures heat that is generated
within
a structure and, to that extent, constitutes an unreasonable intrusion on one’s Fourth Amendment privacy. The Ishmaels, echoing the district court below,
see Ishmael,
The Ishmaels overstate the device’s capabilities. The device “does not intrude in any way into the privacy and sanctity of a home.”
Myers,
46 F.3d
at
669. It “is a passive, non-intrusive instrument” in that “[i]t does not send any beams or rays into the area on which it is fixed or in any way penetrate structures within that area.”
Penny-Fee-ney,
'
The
manner
in which a thermal imager was used in this case is equally significant in assessing the reasonableness of the intrusion. When the DEA performed its pre-dawn thermal readings in this case, the officers never
physically
invaded the Ishmael’s residential or commercial curtilage.
See Dow Chemical,
Similarly, the officers in this case were entitled to observe the steel building either by air or on foot because the building, like the barn in Pace, stood in an open field. And, as we have already discussed, the fact that the officers enhanced their observations with a thermal imager does not require a different conclusion. The device, when used in an “open field,” does not offend the Fourth Amendment because it is passive .and non-intrusive. The sanctity of one’s home or business is undisturbed. We therefore conclude that the DEA’s warrantless use of a thermal imager in this case was not an unconstitutional search.
III.
Having concluded that the warrantless use of a thermal imager was not unconstitutional in this case, we now turn to the question of whether the device’s readings, in conjunction with the remainder of the evidence the DEA proffered to the magistrate judge, established the necessary probable cause to issue the warrant. In determining whether probable cause exists, “a magistrate judge must ■make a practical, common-sense decision as to whether, given all the circumstances set forth in the affidavit, there is a fair probability that contraband or evidence of a crime will be found in a particular place.”
United States v. Byrd,
The totality of the circumstances in this case clearly indicates a fair probability that the Ishmaels were cultivating marijuana in the steel building’s substructure. Rohn Ishmael, for example, was extremely careful not to reveal the need for the concrete remix. The substructure had been elaborately constructed with its own electricity supply and was being fed water from the nearby pond. The substructure’s exhaust fan operated on a continuous basis. In addition, the Ishmaels phone records indicated that their phone had been used to call various horticulture shops, two of which appeared on a law enforcement computer data base. The Ishmaels’ electric utility records demonstrated that the substructure was consuming an inordinate amount of power, particularly when compared to the mobile home’s power usage. Finally, and perhaps most importantly, expert thermographers analyzed the two readings from the thermal imager and concluded that the inordinate amount of heat emanating from the substructure wás consistent with indoor cultivation of marijuana. Construing this evidence in a “common-sense manner,”
9
we conclude that probable cause existed for the issuance of the warrant.
See Robertson,
IV.
For the reasons stated above, the district court’s order granting the Ishmaels’ motion to suppress is REVERSED and the case is REMANDED to the district court for further proceedings.
Notes
.
See United States v. Myers,
. In
United States v. Broussard,
.
Riley
is further proof that a dweller need not guard against every possibility of detection in order to satisfy
Katz'
first prong. The defendant • in
Riley
was cultivating marijuana in a greenhouse that was missing several corrugated roofing panels. Flying over the greenhouse in a helicopter at 400 feet, the police observed marijuana through an opening in the roof. The Court found that the defendant “no doubt intended and expected that- his greenhouse would not be open to public inspection."
Riley,
See also 1 Wayne R. LaFave, Search and Seizure § 2.1(c), at 308-310 (2d ed. 1987) (generally arguing that courts should avoid the contemplation of unreasonable hypotheticals when applying the first Katz prong); David H. Steinberg, Constructing Homes for the Homeless? Searching for a Fourth Amendment Standard, 41 Duke LJ. 1508, 1516-20 (1992).
. "Nothing in the Fourth Amendment prohibited the police from augmenting the sensory faculties bestowed upon them at birth with such enhancement as science and technology afforded them in this case."
Knotts,
. The Ishmaels also overstate its accessibility, which also is a significant consideration. See
Dow Chemical,
The technology employed is "off the shelf,” having been in general use for fifteen years. The device is utilized by many businesses for a variety of purposes, including the detection of roof leaks, steam pipe leaks, cracks in high voltage transmission lines and overloaded transformers. Several companies market the product, which is readily available through purchase, rental or the services of a thermog-rapher.
Deaner,
. We would reach the same conclusion even if we could apply a more exacting standard of review. Applying the four factors from
United States v. Dunn,
. In
Dunn,
which involved facts nearly identical ■ to those in
Pace,
the Supreme Court accepted for the sake of argument that the defendant's barn was a business.
Dunn,
the offic.ers never entered the bam, nor did they enter any other structure on respondent's premises. Once at their vantage point, they merely stood, outside the curtilage of the house and in the open fields upon which the barn was constructed, and peered into the barn’s open front. And, standing as they were in the open fields, the Constitution did not forbid them to observe the phenylacetone laboratory located in respondent's barn. This conclusion flows naturally from our previous decisions.
Id.
at 304,
. "Like the district court, ... we construe the [government's] affidavit-in a common-sense manner.”
McCarty,
