X-Ray Vision: The Constitution’s Kryptonite? Not quite.

By Henry Lininger

Henry Lininger is a Wayne Morse Public Policy Scholar with sophomore standing at the University of Oregon, where he is studying philosophy, ethics and political science. His articles have appeared in publications affiliated with Cornell, Duke and Yale.

Last year, when director Zack Snyder was editing the film Batman v. Superman: Dawn of Justice, he scrapped a scene in which Superman used his x-ray vision to scan the interiors of buildings. [1] Snyder wondered whether this power was too great. Snyder decided that Superman had to forbear from peering through walls, because such surveillance would have made him omniscient -- an unsettling idea for the director and, potentially, for the movie-going public as well.      In the summer of 2017, major advances in technology have given U.S. law enforcement officers the functional equivalent of Superman’s x-ray vision. The question posed by Snyder has become even more salient: Under what circumstances -- if at all -- should police use this awesome power?

The Supreme Court case that came closest to addressing this issue was Kyllo v. United States. [2] In that case, the Court evaluated whether the Fourth Amendment permitted the warrantless use of a thermal imaging device to determine the amount of heat emanating from various parts of a residence in Florence, Oregon. [3] At the time of the original investigation, this device was cutting-edge technology  and was not in wide use.  ​

The officers in Kyllo found an abnormal amount of heat was coming from the roof of the defendant’s home. They inferred that the defendant was using high-energy halide lights in connection with a marijuana growing operation. The officers relied on the readings from the thermal imager to obtain a search warrant. When they executed the warrant, they did indeed find evidence of a marijuana grow. The defendant moved to suppress the evidence, claiming that the thermal imager essentially looked inside his residence before the officers had a warrant.

The Supreme Court ruled in favor of the defendant. Writing for the majority, Justice Antonin Scalia held that the government’s use of a thermal imager violated the defendant’s Fourth Amendment rights. The measurement of heat emanating from the defendant’s home was a residential search and was invalid without a warrant. The subsequent search pursuant to a warrant was also invalid to the extent that the affidavit for the warrant relied on the data from the thermal imager. [4]         
                   
Justice Scalia rejected the government’s argument that the officers simply measured waste heat on the outside of the residence -- an area where the defendant had less privacy. [5] The Court held that the surveillance of a home is a search when “the Government uses a device that is not in general public use” to “explore details of the home that would previously have been unknowable without physical intrusion.” [6]

In a footnote to his Kyllo opinion, Justice Scalia observed that the “ability to ‘see’ through walls and other opaque barriers is a clear, and scientifically feasible, goal of law enforcement research and development.” [7] Few could have foretold at the time of the Kyllo ruling, however, that such technology would be available to the government as soon as 2017.        

Researchers have recently invented drones that can use Wi-Fi signals to conduct through-wall surveillance. [8] This technique can produce highly detailed three-dimensional images of building interiors by emitting Wi-Fi signals that can penetrate brick or concrete walls, as demonstrated by this video. [9, 10] Because of the device’s effectiveness, law enforcement agencies and the military are eager to use the new technology. [11]        

Handheld devices are also becoming available that use radar signals to determine the activity going on inside a residence. [12] The radar can sense even the slightest movement, such as breathing. [13] The radar provides such precise information that it can even determine whether occupants of a residence are engaged in sexual relations. [14]  The new technology is fairly inexpensive, so law enforcement agencies at all levels are clamoring to acquire the devices. One reporter found in 2015 that approximately 50 law enforcement agencies, including the FBI and the U.S. Marshals Service, had already purchased the handheld radar that enables through-wall surveillance. [15]

There can be little doubt that some agencies are using through-wall surveillance without search warrants. While the extent of warrantless surveillance is difficult to gauge, some observers have reported that it does occur. [16]  The possibility of warrantless through-wall surveillance has drawn protests from congressional leaders and scholars. [17, 18] Supreme Court Chief Justice John Roberts has flagged the issue of warrantless through-wall surveillance as an important one for the Court to resolve, and newly appointed Justice Neil Gorsuch has noted the potential for abuse of such surveillance, but so far a case presenting this precise issue has not yet reached the Court. [19, 20]

Will the Kyllo ruling adequately regulate the new technology? At first blush, Kyllo seems to be a useful precedent, because it limits through-wall surveillance that could allow police to “explore details of the home.” [21] But there are three reasons to believe that Kyllo is ill suited to protect against the threat to privacy posed by the latest technology.

First, Kyllo only applies when the government offers evidence against the accused in a criminal prosecution. If the government uses through-wall surveillance but does not follow up with a criminal prosecution that rests on evidence attributable to this surveillance, Kyllo provides no remedy. [22] In many cases, the subject may never learn that the government has monitored the subject’s residence.                 

Second, the doctrine of “exigent circumstances” creates a loophole in the Kyllo rule. Police may dispense with the normal privacy rules -- and with the Fourth Amendment’s requirement of a warrant -- if the officers reasonably believe that doing so is necessary to prevent the destruction of evidence, to protect the safety of officers or occupants, or to avert other categories of harm. [23] Much of the marketing for the new through-wall surveillance suggests that it is useful to deal with exigent circumstances. [24] So long as officers can identify some ostensible and plausible concern about exigency that motivates their use of through-wall surveillance, Kyllo will not stand in their way.

Third, Kyllo only applies to technology that is not in widespread use. [25] In other words, Kyllo provides no remedy if police utilize technology that is accessible to the general public. Justice Scalia was not entirely clear about the reasons for the exemption of widely used technology, but he apparently assumed that general availability of technology should shrink the reasonable expectation of privacy vis-a-vis such technology. When he conditioned privacy on the accessibility of technology, Justice Scalia seems to have underestimated the capacity of the tech industry to manufacture surveillance devices cheaply and sell them on the open market. In 2017, private homeowners are now interested in through-wall surveillance for various purposes, including detection of intruders. [26] It seems likely that the devices capable of through-wall surveillance will soon be in general use. Ironically, the protection provided by Kyllo fades as the devices threatening that privacy become more readily available. [27]

In sum, the Kyllo ruling will have limited utility in protecting homeowners’ privacy against through-wall surveillance. The time has come for comprehensive federal legislation to address this issue. The bipartisan commitment to the sanctity of the home presents an unusual opportunity for a legislative solution. [28] Until that time, while the case  can limit some uses of through-wall surveillance by police gathering evidence for criminal trials, Kyllo is unlikely to be the kryptonite that disables x-ray vision.


[1]Mark Julian, “Zack Snyder Explains Superman’s Reluctance to Utilize Super Hearing and X-Ray Vision,” comicbookmovie.com, Apr. 8, 2016. Accessed July 1, 2017. https://www.comicbookmovie.com/batman_vs_superman/zack-snyder-explains-supermans-reluctance-to-utilize-super-hearing-and-x-ray-vision-a137234
[2] 533 U.S. 27 (2001). Accessed July 1, 2017.
https://supreme.justia.com/cases/federal/us/533/27/case.html
[3] The search at issue in Kyllo occurred only a short distance from this author’s home in Lane County, Oregon. Defendant Danny Kyllo has become something of a local hero for standing up to high-tech surveillance and changing the law of residential privacy throughout the U.S. Kyllo maintains a website, www.dannyleekyllo.com, about his experience during and after the decade-long prosecution.
[4] Kyllo, supra n. 3, at 40.
[5] Id. at 35.                                       
[6] Id. at 40.
[7] Id.at36n.3.
[8] Katyanna Quach “No, Really. You Can See Through Walls Using Drones and Wi-Fi,” Register, June 20, 2017. Accessed July 1, 2017.
https://www.theregister.co.uk/2017/06/20/drones_and_wifi_see_thru_ walls/
[9] Chitra Karanam and Yasamin Mostofi, “3D Through-Wall Imaging with Unmanned Aerial Vehicles Using WiFi,” paper presented at 16th annual International Conference on Information Processing in Sensor Networks, April 2017. Accessed July 1, 2017.
http://www.ece.ucsb.edu/~ymostofi/papers/IPSN17KaranamMostofi.pdf
[10] Sonia Fernandez, X-Ray Eyes in the Sky,” U,C, Santa Barbara Current, June 19, 2017. Accessed July 1, 2017. www.news.ucsb.edu/2017/018068/x-ray-eyes-sky
[11] Dave Mosher, “The U.S. Government Is Eyeing a Technology That Can 3D-Phography People Through Walls Using Wi-Fi, Business insider, May 30, 2017. Accessed July 1, 2017. http://www.businessinsider.com/us-military-may-want-wifi-holography-device-2017-5
[12] Brittany Puckett, “Mighty Morphin’ Power Range-R: The Intersection of the Fourth Amendment and Evolving Police Technology,” 8 Elon L. Rev. 555, 556-57 (2016). Accessed July 1, 2017. https://www.elon.edu/e/CmsFile/GetFile?FileID=559
[13] “Range-R Theory of Operation,” Range-R Through the Wall Radar. Accessed July 1, 2017. http://www.range-r.com/tech/theory.htm
[14] Michael Reschke, “Expert Concerned About Use of Radar Devices,” Govt. Tech., Jan. 23, 2015 (quoting Prof. Fred Cate at Indiana University). Accessed July 1, 2017. http://www.govtech.com/public- safety/Expert-Concerned-About-Use-of-Radar-Devices.html
​[15] Brad Heath, “New Police Radars Can “See” Inside Homes, U.S.A. Today, Jan. 20, 2015. Accessed July 1, 2017. https://www.usatoday.com/story/news/2015/01/19/police-radar-see-through- walls/22007615/
[16] Jerry Chapin, “New Radar Technology Used by Law Enforcement Presents Privacy Concerns,” J. High Tech. L., Feb. 19, 2015. Accessed July 1, 2017.
https://sites.suffolk.edu/jhtl/2015/02/19/new-radar- technology-used-by-law-enforcement-presents-privacy-concerns/
[17] Letter from U.S. Senator Chuck Grassley (R-IA) and U.S. Senator Patrick Leahy (D-VT) to U.S. Attorney General Eric Holder, Jan. 22, 2015. Accessed July 1, 2017.
https://www.leahy.senate.gov/imo/media/doc/012215%20Grassley-Leahy%20to%20Holder%20on%20radar%20technology.pdf
[18] E.g., Puckett, supra n. 13; Reschke, supra n. 15.
[19] Mike Tolson, “Chief Justice Roberts: Technology Among Top Issues for Court, Houston Chronicle, Oct. 17, 2012. Accessed July 1, 2017. http://www.chron.com/news/houston-texas/houston/article/Chief-Justice-Roberts-Technology-among-top-3957626.php
[20] United States v. Denson, 775 F.3d 1214, 1218-19 (10th Cir. 2014) (Gorsuch, J.). Accessed July 1, 2017. http://caselaw.findlaw.com/us-10th-circuit/1688123.html
[21] Kyllo, supra n. 3, at 40.                         
[22] Denson, supra n. 21, at 1218-19.
[23]  Valerie Van Brocklin, “Cops That Can ‘See Through Walls?’ Facts About the X-Ray Uproar,” Police One, Jan. 28, 2015. Access July 1, 2017.
https://www.policeone.com/legal/articles/8194196-Cops-that- can-see-through-walls-Facts-about-the-X-ray-uproar/
[24] E.g., “Typical Range-R Applications,“ Range-R Through the Wall Radar. Accessed July 1, 2017. http://www.range-r.com                                  
[25]  Kyllo supra n. 3, at 40.
[26]  Matthew Braga, “This Box Can See Through Walls -- and It Could Shake Up Home Security,” CBC News, Apr. 28, 2017. Accessed July 2, 2017.
http://www.cbc.ca/news/technology/aura-cognitive-systems-home-security-wireless-spectrum-1.4086660
[27] Id. at 47 (Stevens, J., dissenting).
[28] Letter from Grassley and Leahy, supra n. 18.
Photo Credit Flickr User: West Midlands Police "This photo shows an aerial thermal image taken by the Force Helicopter that highlights a Cannabis Factory."

The opinions and views expressed through this publication are the opinions of the designated authors and do not reflect the opinions or views of the Penn Undergraduate Law Journal, our staff, or our clients.

A Note from the Author:
This article is based on research for an affirmative case in policy debate. I am grateful for guidance I received from Alexander Erwig, a student at Harvard Law School, who was my debate coach and instructor in debate classes at the University of Oregon until June 2017. Thanks also to my father Tom Lininger, a law professor at the University of Oregon, who helped with editing this article.