By Mike Petridis
Kyllo v. United States created a rule with an unnecessary test that allows a home, a person’s castle, to be searched without a warrant. The Kyllo rule states: “[O]btaining by sense-enhancing technology any information regarding the interior of the home that could not otherwise have been obtained without physical ‘intrusion into a constitutionally protected area’ constitutes a search — at least where . . . the technology in question is not in general public use.” This rule was intended to be forward-looking and anticipate future technology. However, the “general public use” test is a loophole that can be used by law enforcement officers to conduct warrantless searches of homes in violation of Fourth Amendment principles.
Danny Kyllo’s home was scanned by an Agema Thermovision 210, a thermal imager, after law enforcement officials suspected him of growing marijuana. The scan of the home determined that certain areas of the house were significantly warmer than surrounding homes. The temperature difference indicated a strong possibility that Kyllo was running halide lights, which are used in the growing of marijuana. Based on the thermal imaging, informants, and utility bills, law enforcement officials were able to obtain a search warrant for Kyllo’s home. When agents searched the house, they found more than 100 marijuana plants. Kyllo was charged with “one count of manufacturing marijuana.” Kyllo moved to suppress the evidence but suppression was unsuccessful, and Kyllo “entered a conditional guilty plea.” As a result, “[t]he Court of Appeals for the Ninth Circuit remanded the case for an evidentiary hearing regarding the intrusiveness of thermal imaging.” On remand, the District Court of Oregon found that the Agema 210 was not intrusive because it did not penetrate the walls or allow observation of intimate details within the home. The Ninth Circuit Court of Appeals held that Kyllo had no subjective expectation of privacy in regards to the heat leaving his home and that there was no “objectively reasonable expectation of privacy because the imager did not expose any intimate details.” The Supreme Court held that the Agema 210 scan was a search under the Fourth Amendment because a device that is not in “general public use” explored details of a home that could only be found through physical intrusion.
This blog will examine how the “general public use” test creates a loophole that allows for unwarranted searches that violate the purpose of the Fourth Amendment. Section II will examine the original reasons behind the Fourth Amendment. These reasons will then be applied to crafting a principle of the Fourth Amendment. Section III will provide an overview of current “see through the wall” technology available to law enforcement. In addition, this section will compare thermal imaging as it was when the Court decided Kyllo to the current state of thermal imaging. Section IV is an attempt to define in “general public use” and will examine how lower courts have dealt with the test. Except for a brief mention in a footnote, the Supreme Court did not provide any definition or formula to determine when the technology is in general public use. The lower courts have struggled to use this test and instead avoid it entirely, ruling on cases by using other elements of the case. Section V will examine Supreme Court cases that involved advanced technology relative to the time the case was decided. These cases could provide guidelines on how a court should handle advanced sensing technology. After examining these cases, Section VI will conclude by arguing that in order to preserve the spirit of the Fourth Amendment, the Supreme Court needs to eliminate the “general public use” test and only use the property test.
II. What is the Principle of the Fourth Amendment?
The Fourth Amendment provides “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” Searching for the original meaning in an amendment provides inherent difficulties because the Framers “had no opportunity to confront [modern practices] or to consider the fundamentally different social conditions of today.” With this caveat in mind, a court can still determine the general scope of protection by the circumstances the Framers were responding to when drafting the Fourth Amendment. The Fourth Amendment was created to protect against general warrants and writs of assistance.
In considering the Framers’ intent, the principle of the Fourth Amendment can be reasoned as a protection against physical intrusions into the home. The home has enjoyed a special protection from very early times and can be viewed as the place where individuals are free to enjoy the privileges afforded to them by a democratic society.
These ideas form the traditional property-based Fourth Amendment jurisprudence. In Katz v. United States, the Supreme Court seemingly abandoned this view of the Fourth Amendment. However, in Florida v. Jardines, the Court established that the Fourth Amendment property-based analysis is the minimum level of protection provided to people in their homes. Following Jardines, the property-based analysis of the Fourth Amendment recognizes certain areas as constitutionally protected against physical and intangible intrusions. The “general public use” test is a loophole that can violate constitutionally protected areas.
III. Current Advanced Sensing Technology
There are currently several hand-held devices that the National Institute of Justice has classified as through-the-wall sensors (“TTWS”). These devices include: Range-R series, Xaver series, Retwis 5, and the Eagle5-NCL. TTWS devices use radar transmitted at low power and across several frequencies. The radar penetrates walls and reflects when it comes into contact with an object or different materials. As the radar reflects off the objects or materials, the frequency shifts and the measurement “distinguishes between stationary and moving objects.” When radar passes through objects, it becomes attenuated. Attenuation is the loss of signal strength. Attenuation is reduced by using a wide range of frequencies to “probe” the area. To provide as much information about the area being “probed” and to minimize attenuation problems, TTWS devices will use either a Pulse Wave System or a Ultra-Wide Band Pulse System (“UWB”). The difference between these two systems is the amount of information they relay back to the device. One specific limitation of the technology is that it cannot “see through solid metal surfaces,” but it can operate through concrete and wood.
The devices can display information gathered in 1 degree (“d”), 2d, or 3d. Other differences between the devices include various technical specifications, such as the degrees of the field of view, maximum distance of the scan, weight, and battery life. Additionally, the devices also differ in price. For example, a Range-R will cost $6,000 while a Xaver-400 will cost $47,500.
Current thermal imagers are superior to the Agema-210 used in Kyllo. Heat detecting devices have been around for several decades. Infrared thermal imaging devices have continued to advance from the time of the Kyllo decision; many different models are now available to the average person. These products are cheaper than the Agema-210 and provide more detail and accuracy than the Agema-210.
IV. How Have the Lower Courts Dealt with the General Public Use Test and How Can General Public Use Be Defined
In Kyllo, the Supreme Court did not provide a definition or an outline to determine when an item is in “general public use.” Because the Supreme Court did not provide direction for the lower courts, the resulting jurisprudence has not been consistent. Courts have avoided determining whether an item is in “general public use,” unless the item, such as a camera, is easily considered to be in “general public use.”
A state appeals court avoided examination of an item’s “general public use” in McClelland v. State. Daryl J. McClelland was arrested by police officers who were investigating individuals that downloaded child pornography. The police officers traced McClelland’s Wi-Fi signal using a Yagi antenna. At trial, McClelland moved to suppress the child pornography found on his computer on the grounds that the Yagi antenna “constituted an enhanced technology which breached the expectation of privacy that McClelland had within his motorhome.” The trial court concluded that McClelland did not have a reasonable expectation of privacy because he was broadcasting signals outside his motorhome and that the use of the Yagi antenna was lawful because it was in “general public use.” The Florida District Court of Appeal reviewing the case declined to examine the issue of “general public use” because McClelland did not have an expectation of privacy.
Courts have decided night vision goggles, flashlights, and cameras are in “general public use.” However, courts have not provided an in-depth analysis as to why these products are in the “general public use.” Flashlights or cameras do not require an in-depth analysis because of their availability as consumer products for decades. As for the night vision goggles, the court in United States v. Vela reasoned that “they are available to the public via internet. More economical night vision goggles are available at sporting goods stores. Therefore, night vision goggles . . . are available for general public use.”
The definitions section of the Federal Acquisition Regulations System provides factors that classify an item as a commercial item. An analogy can be drawn between a commercial item and “general public use.” The factors that define an item as commercial can be used to determine if the item should be considered in “general public use.” Under § 2.101, there are eight types of items that are considered commercial items. Relevant portions include:
(1) Any item, other than real property, that is of a type customarily used by the general public or by non-governmental entities for purposes other than governmental purposes, and—
(i) Has been sold, leased, or licensed to the general public; or
(ii) Has been offered for sale, lease, or license to the general public.
When considering these factors, an item is in “general public use” when two conditions are met. First, the item is not restricted to governmental agency use. Second, a person can buy, sell, or lease the item.
V. Courts Should Analyze Advanced Sensing Technology Under a Property Analysis
While it is impossible to predict the exact path technology will take, the trend is usually for smaller and more portable uses. The evolution of the infrared camera displays this trend; the infrared camera evolved from large bulky devices to attachments that people can place on a phone. A corollary to this progress is that devices created for the military might become available for the general public; an example of this progress is the internet and GPS devices. With this trend in mind, judging the validity of a search on whether the public is using an item is a precarious position.
In assessing the proper lens to view advanced sensing technology searches, the courts should analyze how the Supreme Court has dealt with other types of technology and its rationale in those cases. The Supreme Court has held that an electronic listening device placed on the outside of a telephone booth was a search under the Fourth Amendment, requiring a search warrant. The Government argued that there was no reason to invoke the Fourth Amendment because there was “no physical penetration of the telephone booth.” The Court reasoned that the Fourth Amendment protects “people – and not simply ‘areas.’” The Fourth Amendment principle derived from Katz is that a search has not occurred “unless ‘the individual manifested a subjective expectation of privacy in the object of the challenged search, and ‘society [is] willing to recognize that expectation as reasonable.’” Thus, Katz asserted that “privacy, not property, was a centralizing principle upon which the Fourth Amendment rights were premised.”
The Court has also ruled that a software that is used to locate computers that are piggy-backing onto other Wi-Fi routers is not a Fourth Amendment search. The Court justified this position under two rationales. First, if a person is intentionally sharing their activities outside of the confines of the home, then the privacy protections afforded by the home are lost. Second, a person who uses a third-party Wi-Fi router without consent in an attempt to disguise a signal’s origin has no legitimate expectation of privacy.
While not strictly human-made like other technologies, narcotics sniffing dogs can also be described as a sense enhancing technology. Justice Scalia, writing for the majority, decided Jardines on property grounds. The government argued that no privacy interest was violated when the narcotics dog sniffed around the outside of the house. However, as Justice Scalia explained, the home and curtilage are constitutionally protected areas that are unaffected by expectations of privacy. If a constitutionally protected area is intruded upon without authorization, then a violation of the Fourth Amendment has occurred. Justice Kagan, in a concurring opinion, reasoned that the case could have been decided using Kyllo. A narcotics sniffing dog is similar to a sense enhancing tool that is not in “general public use” because the narcotics dog can explore details of the home that one could have an expectation of privacy in.
Two principles emerge from the Supreme Court’s jurisprudence on the Fourth Amendment. First, a person has a reasonable expectation of privacy modified by his or her location or behavior. Second, the home has a property-based protection. Advanced sensing technology searches should be analyzed under the property rubric. Similar to the Jardines property-based ruling, a police officer should not be allowed to invade a home’s curtilage to use a handheld or portable advanced sensing device to exam the interior of the home. Additionally, as the property-based analysis also protects against intangible intrusions of a constitutionally protected area, a search of a home beyond the curtilage with advanced sensing technology should also not be allowed. The property-based analysis provides a-bright line rule that is easy for the courts to use. The property-based analysis is the Kyllo rule without the “general public use” test. Without the “general public use” test, the Kyllo rule is “[w]here, as here, the Government uses a device . . . to explore details of the home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively unreasonable without a warrant.”
The rule would not be complete without the exigent circumstances exception. The use of advanced sensing technology should be allowed in those situations. Further, the naked eye observation of a law enforcement official should also be accounted for. A reasonable application of the naked eye observation exception is illustrated by a hypothetical scenario. A police officer views contraband or illegal activity through a window from a public area. The police officer can then, within a reasonable time frame from the observation, use the advanced sensing technology to provide further information. Of course, even under the naked eye observation, the officer should be held to the exigency standard. The situation must call for a “warrantless search [that] is objectively reasonable under the Fourth Amendment.” Therefore, if the situation observed meets the exigency standard for warrantless entry, then it follows that an advanced sensing search would also be valid.
The Court intended the Kyllo rule as a bright-line test for the use of sense enhancing technology. However, the addition of the “general public use” test defeats that purpose. Technology that can see into a home is arguably moving into “general public use.” Additionally, courts struggle to apply the “general public use” test. In order to preserve the spirit of the Fourth Amendment and provide a clear guide to the lower courts, searches involving advanced sensing technology should be analyzed under a property analysis. Advanced sensing technology that is used by invading the curtilage of the home or penetrating the walls to see into the interior of the home is presumptively unreasonable and requires a warrant. Therefore, the property analysis should provide coverage well into the future as science creates new methods to see the unseen.
 533 U.S. 27 (2001).
 Id. at 34 (citation omitted).
 Id. at 36. “[T]he rule we adopt must take account of more sophisticated systems that are already in use or in development.” Id.
 Id. at 29.
 Id. at 30.
 Id. at 31.
 Id. at 40.
 Id. at 39 n.6.
 U.S. Const. amend. IV.
 James J. Tomkovicz, Beyond Secrecy for Secrecy’s Sake: Toward an Expanded Vision of the Fourth Amendment Privacy Province, 36 Hastings L.J. 645, 671 (1985).
 “The general warrant, issued by a magistrate, provided government officials with an unlimited ability to search the home of anyone listed in the warrant, regardless of the nature of the violation alleged.” Quin M. Sorenson, Comment, Losing a Plain View of Katz: The Loss of a Reasonable Expectation of Privacy Under the Readily Available Standard, 107 Dick. L. Rev. 179, 181 n.14 (2002).
 “The writ of assistance is most easily described as a form of a general warrant. Under a writ of assistance, issued by a magistrate, customs officials could engage in arbitrary and effectively limitless searches of any home in which they suspected that prohibited goods may be located.” Id. at 181 n.15.
 Tomkovicz, supra note 18, at 673.
 Id. “The poorest man may, in his cottage, bid defiance to all the forces of the Crown. It may be frail . . . but the King of England may not enter; all his force dares not cross the threshold of the ruined tenement.” Id. at 673 n.120.
 See id. at 674.
 See Olmstead v. United States, 277 U.S. 438 (1928), overruled by Katz v. United States, 389 U.S. 347 (1967) (holding that the Fourth Amendment only involves tangible seizures or physical intrusions).
 389 U.S. 347 (1967).
 See id. at 353. “[I]t becomes clear that the reach of [the Fourth] Amendment cannot turn upon the presence or absence of a physical intrusion.” Id.
 569 U.S. 1 (2013).
 See id. at 11.
 See Carpenter v. United States, 138 S. Ct. 2206 (2018); Collins v. Virginia, 138 S. Ct. 1663 (2018).
 See Carpenter, 138 S. Ct. at 2214 (“[W]e rejected in Kyllo a ‘mechanical interpretation’ of the Fourth Amendment.”) (citation omitted)).
 The Range-R series includes several models: The Range-R, Range-R Link, Range-R 2d, Range-R 2d Link. Security & Detection Systems, L3Harris, https://www.sds.l3t.com/military-first-responders/RANGE-R.htm (last visited Aug. 31, 2019).
 Types of radar used includes: Continuous Wave System, Pulse Wave System, and Ultra-Wide Band Pulse System. ManTech Advanced Sys. Int’l. Inc., U.S. Dep’t of Justice, Through-the-Wall-Sensors for Law Enforcement: Market Survey 9-14 (2012), https://www.justnet.org/pdf/00-WallSensorReport-508.pdf [hereinafter Market Survey].
 Market Survey, supra note 35, at 4.
 Id. at 4.
 Id. at 5.
 See id. at 5-6.
 See id. at 4-6, 11-14.
 Lewis, supra note 36, at 1.
 Market Survey, supra note 35, at 4.
 1d, 2d, and 3d is shorthand for the dimensions provided by the display. The difference between 1d and 2d is that 1d provides the range and status (moving/breathing) of the target and 2d will provide a graphic display of the area scanned, such as the general shape of the room, and multiple persons in the room. See ManTech Advanced Sys. Int’l. Inc., U.S. Dep’t of Justice, Through-the-Wall-Sensors for Law Enforcement: Best Practices 10 (2014), https://www.justnet.org/pdf/ThroughWallSensorBestPractices-508.pdf.
 Market Survey, supra note 35, at 11-16.
 Id. at 15.
 Kyllo v. United States, 533 U.S. 27, 29-30 (2001).
 The first thermographic camera was created by Kálmán Tihanyi in 1929. Nic Fleming, The Man who Makes you See the Invisible, BBC (June 14, 2017), https://www.bbc.com/future/article/20170614-thermal-imaging-reveals-the-hidden-heat-lost-from-your-home.
 At the time of this writing, 30 products are available and some products have different models. See Handheld Thermal Cameras, FLIR, https://www.flir.com/browse/industrial/handheld-thermal-cameras/?page=2 (last visited Mar. 8, 2020). Thermal cameras can also attach to a smartphone. FLIR ONE Pro, FLIR, https://www.flir.com/products/flir-one-pro/?model=435-0006-02 (last visited Mar. 8, 2020). The PerfectPrime is an infrared camera available on Amazon that comes in different models and ranges in price from $129.99 to $299.99 at the time of this writing. PerfectPrime IR0002 Thermal Camera, amazon, https://www.amazon.com/Perfect-Prime-IR0001-Infrared-Resolution Temperature/dp/B075F61GFH?ref_=fsclp_pl_dp_5 (last visited Apr. 20, 2020).
 Considering the time when the Agema-210 was used, it probably cost at least $10,000. See Adam W. Brill, Kyllo v. United States: Is the Court’s Bright-Line Rule on Thermal Imaging Written in Disappearing Ink?, 56 Ark. L. Rev. 431, 433 n.13 (2003) (reporting that thermal imagers range from $15,000 to $35,000); see also Ed Kochanek, Thermal Imaging from the Beginning of the Thermographer’s Camera to the Present, IRINFO.Org, https://irinfo.org/12-1-2013-kochanek/ (last visited Sept. 15, 2019) (explaining that a thermal camera sold for $25,000 in 1997).
 Contrast the Agema-210 technical specification with a $10,000+ modern model or the smartphone camera. Agema Infrared Systems, THERMOVISION 210 Series Operating Manual Section 6 at 1-9 (2002), https://support.flir.com/DocDownload/Assets/dl/1557627$a.pdf; Agema Infrared Systems, Thermovision 400 & 200 (1990), https://support.flir.com/DocDownload/Assets/dl/1557569$a.pdf; FLIR, Technical Data FLIR T5xx Series (2019), https://support.flir.com/DocDownload/Assets/dl/t810463-en-us.pdf; FLIR, FLIR One Pro, https://support.flir.com/DocDownload/Assets/dl/17-1746-oem-flir_one_pro_datasheet_final_v1_web.pdf (last visited Oct. 21, 2019).
 Kyllo, 533 U.S. at 39 n.6 (“Given that we can quite confidently say that thermal imagining is not ‘routine,’ we decline in this case to reexamine that factor.”).
 See McClelland v. State, 255 So. 3d 929 (Fla. Dist. Ct. App. 2018); United States v. Hachey, No. 16-0128, 2017 U.S. Dist. LEXIS 34192 (E.D. Pa. 2017); United States v. Vela, 486 F. Supp 2d 587 (W.D. Tex. 2005); United States v. Deleston, No. 15-cr-113, 2015 U.S. Dist. LEXIS 107341 (S.D.N.Y. 2015); Idaho v. Howard, No. CR-2011-2029, 2012 Ida. Dist. LEXIS 31 (Idaho 2012).
 McClelland, 255 So. 3d 929.
 Id. at 930-31.
 Id. at 931.
 Id. at 932.
 Id. at 932 n.2 (“It is unnecessary for us to make any determination regarding whether this was an accurate conclusion due to our agreement with the trial court that McClelland lacked an expectation of privacy that society would be willing to recognize as reasonable.”).
 See United States v. Vela, 486 F. Supp. 2d 587 (W.D. Tex. 2005); United States v. Deleston, No. 15-cr-113, 2015 U.S. Dist. LEXIS 107341 (S.D.N.Y. 2015); Idaho v. Howard, No. CR-2011-2029, 2012 Ida. Dist. LEXIS 31 (Idaho 2012).
 See cases cited supra note 62.
 486 F. Supp. 2d 587 (W.D. Tex. 2005).
 Id. at 590.
 48 C.F.R. § 2.101 (LEXIS through the Sept. 9, 2019 issue of the Federal Register).
 See supra notes 50-53 and accompanying text.
 Evan Andrews, Who Invented the Internet?, History, https://www.history.com/news/who-invented-the-internet (last updated Oct. 28, 2019).
 Global Positioning System History, NASA, https://www.nasa.gov/directorates/heo/scan/communications/policy/GPS_History.html (last updated Aug. 7, 2017).
 See Katz v. United States, 389 U.S. 347, 358-59 (1967).
 Id. at 352.
 Id. at 353.
 Kyllo v. United States, 533 U.S. 27, 33 (2001) (citation omitted).
 Thomas K. Clancy, The Fourth Amendment Its History and Interpretation 88 (2nd ed. 2014).
 The software in this case is called a MoocherHunter. It is a software tool that uses a laptop and a directional antenna. “The user enters the MAC address of the wireless card he wishes to locate and the program measures the signal strength of the radio waves emitted from this card.” United States v. Stanley, 753 F.3d. 114, 115-17 (3d Cir. 2014).
 See id. at 124.
 Id. at 119-20.
 Id. at 120-21 (“Stanley, was, in effect, a virtual trespasser.”).
 Florida v. Jardines, 569 U.S. 1, 14-15 (Kagan, J., concurring).
 See id. at 3-12. “The Katz reasonable-expectations test ‘has been added to, not substituted for,’ the traditional property-based understanding of the Fourth Amendment.” Id. at 11 (citation omitted).
 See id. at 10.
 See id. at 5-11.
 Id. at 10-12.
 Id. at 14 (Kagan, J., concurring).
 Id. at 14-15 (Kagan J., concurring).
 See Katz v. United States, 389 U.S. 347 (1967); Kyllo v. United States, 533 U.S. 27 (2001); United States v. Stanley, 753 F.3d 114 (3d Cir. 2014); United States v. Karo, 468 U.S. 705 (1984).
 See Jardines, 569 U.S. at 5-7, 11.
 Id. at 6-7. “We therefore regard the area ‘immediately surrounding and associated with the home’—what our cases call the curtilage—as ‘part of the home itself for Fourth Amendment purposes.’” Id. at 6 (citing Oliver v. United States, 466 U.S. 170, 180 (1984)).
 Kyllo, 533 U.S. at 40.
 Some situations include “hot pursuit,” imminent destruction of evidence, and the preservation of life. See Brigham City v. Stuart, 547 U.S 398, 403-04 (2006).
 See California v. Ciraolo, 476 U.S. 207, 213 (1986) (“The Fourth Amendment protection of the home has never been extended to require law enforcement officers to shield their eyes when passing by a home on public thoroughfares.”).
 Brigham City, 547 U.S. at 403.