Kyllo v. United States: Unwarranted Thermal Search (06/11/01)


Kyllo v. United States

Does the use of a thermal-imaging device to detect heat emanating from a private home constitute as a violation of the Fourth Amendment?

Argued: 02/20/01

Decision Date: 06/11/01

Decision Record: 5-4; yes

Justices in Favor: Antonin Scalia, David Souter, Clarence Thomas, Ruth Ginsburg, Stephen Breyer

Justices Dissenting: William Rehnquist, John Paul Stevens, Sandra Day O’Connor, Anthony Kennedy

Effect of the Decision

This case clarifies that the use of a thermal-imaging device, or any other device used to conduct a search, even from outside the house, is considered unconstitutional if performed without a warrant.

In Favor

In representation of Kyllo, attorney Kenneth Lerner argued, “Our home is the basic refuge for all citizens.

It’s where we have our greatest expectations of privacy, where we are free to let down our guard, and where we should have our greatest feeling that we are free from government spying.

Unreasonable and unwarranted searching of the home is the chief evil that the Fourth Amendment protects us against, and it has a specific… the home itself has a specific mention in the Constitution, and as a bedrock principle, the home is a place where we have our most heightened expectations of privacy.

I think that is an incomplete view of thermal imaging because there would be no image at all if it weren’t for the thermodynamic process.

There must be a constant heat source to heat up the wall so that you will see it.

Therefore there is something behind the wall that provides and radiates heat to the wall, the wall reradiates it out, but if it’s not constant, if it’s not a dynamic process, you will not see anything, and therefore it is the purpose of the thermal imager and the function of the thermal imager is to detect what is beneath the surface by scanning that surface.”


Then in opposition, representing the United States, attorney Michael R. Dreeben claimed, “Thermal imaging senses heat gradients on the exterior of a surface, in this case the structure was a house.

It does not penetrate the walls of the house, it does not reveal particular objects or activities inside of a house, and the record in this case and the findings that the district court made indicate that it is not capable of doing so through walls of a house.

The question in this case is whether individuals have a reasonable and justifiable expectation of privacy in the heat that’s on the exterior surface of their walls.

We believe that they do not.

Heat loss is an inevitable feature of heat in a structure.

If a structure is generating heat, it will lose that heat, and everyone knows that.

That’s why there is an insulation industry.

In addition, heat loss is frequently observable without the aid of technology, as, for example, when snow melts on a roof.”


The majority opinion was written by Justice Scalia. He wrote, “We have said that the Fourth Amendment draws “a firm line at the entrance to the house,” Payton, 445 U.S., at 590. That line, we think, must be not only firm but also bright–which requires clear specification of those methods of surveillance that require a warrant. While it is certainly possible to conclude from the videotape of the thermal imaging that occurred in this case that no “significant” compromise of the homeowner’s privacy has occurred, we must take the long view, from the original meaning of the Fourth Amendment forward.

“The Fourth Amendment is to be construed in the light of what was deemed an unreasonable search and seizure when it was adopted, and in a manner which will conserve public interests as well as the interests and rights of individual citizens.” Carroll v. United States, 267 U.S. 132, 149 (1925).

Where, as here, 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, the surveillance is a “search” and is presumptively unreasonable without a warrant.

Since we hold the Thermovision imaging to have been an unlawful search, it will remain for the District Court to determine whether, without the evidence it provided, the search warrant issued in this case was supported by probable cause–and if not, whether there is any other basis for supporting admission of the evidence that the search pursuant to the warrant produced.”

In respectful dissent, Justice Stevens said in his opinion, “The Court argues that the permissibility of “through-the-wall surveillance” cannot depend on a distinction between observing “intimate details” such as “the lady of the house [taking] her daily sauna and bath,” and noticing only “the nonintimate rug on the vestibule floor” or “objects no smaller than 36 by 36 inches.” Ante, at 10—11. This entire argument assumes, of course, that the thermal imager in this case could or did perform “through-the-wall surveillance” that could identify any detail “that would previously have been unknowable without physical intrusion.” Ante, at 11—12. In fact, the device could not, see n. 1, supra, and did not, see Appendix, infra, enable its user to identify either the lady of the house, the rug on the vestibule floor, or anything else inside the house, whether smaller or larger than 36 by 36 inches. Indeed, the vague thermal images of petitioner’s home that are reproduced in the Appendix were submitted by him to the District Court as part of an expert report raising the question whether the device could even take “accurate, consistent infrared images” of the outside of his house. Defendant’s Exhibit 107, p. 4. But even if the device could reliably show extraordinary differences in the amounts of heat leaving his home, drawing the inference that there was something suspicious occurring inside the residence–a conclusion that officers far less gifted than Sherlock Holmes would readily draw–does not qualify as “through-the-wall surveillance,” much less a Fourth Amendment violation.

Although the Court is properly and commendably concerned about the threats to privacy that may flow from advances in the technology available to the law enforcement profession, it has unfortunately failed to heed the tried and true counsel of judicial restraint. Instead of concentrating on the rather mundane issue that is actually presented by the case before it, the Court has endeavored to craft an all-encompassing rule for the future. It would be far wiser to give legislators an unimpeded opportunity to grapple with these emerging issues rather than to shackle them with prematurely devised constitutional constraints.”

My Opinion:

In this case, I agree with the majority decision. The thermal-imaging device used to perform a thermal search is still considered a violation of the Constitution. The search was performed without a warrant, and regardless of the fact that it was done outside, it allowed the searchers to search inside Kyllo’s property, which is evidently a violation of the Fourth Amendment right to “be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” They may not have been able to actually look inside, but it allowed them to find what they were looking for without a warrant, which is not constituted by the Fourth Amendment.

*Justice Leaning L=Left, LC=Left of Center, C=Center, RC=Right of Center, R=Right

Leave a Reply

Your email address will not be published. Required fields are marked *