Kyllo v. United States
533 U.S. 27, 121 S. Ct. 2038, 150 L. Ed.2d 94 (2001)

  • The police suspected Kyllo of using grow-lamps to grow marijuana inside of his home.
  • Realizing that grow-lamps produce a lot of heat, the police used a thermal imaging camera to take photos of Kyllo’s house from a public street. The cameras showed an unusual heat source. The police used this information to obtain a warrant, entered Kyllo’s home, found marijuana plants, and arrested Kyllo for drug possession.
    • The thermal imaging camera emits no beams or rays, it is a passive collection system that only records what is naturally emanating from the target (unlike an x-ray machine which zaps its target with x-rays).
  • At trial, Kyllo made a motion to suppress on the grounds that the thermal camera represented an illegal search of his house and was therefore a violation of the 4th Amendment.
  • The Trial Court denied the motion to suppress. Kyllo appealed.
  • The Appellate Court upheld the conviction. Kyllo appealed.
  • The US Supreme Court reversed and granted the motion to suppress.
    • The US Supreme Court found that thermal imaging of a home constitutes a 4th Amendment search and may be done only with a warrant.
      • The Court found that the general public does not have access to thermal imaging cameras, and therefore there is a presumptive expectation of privacy.
  • In a dissent it was argued that while thermal imaging cameras are not common, there were other ways in which the general public could observe thermal emissions from a house (for example, snow melting on a roof), and therefore there was no violation of the 4th Amendment.
    • Compare to United States v. Karo (468 U.S. 705), where it was suggested that if something could be done without technology, but was easier with the technology, it would be ok to use the technology.
  • The dissent further suggested that the thermal camera only measures the temperature of the outside wall of the house, it says nothing about what is inside. Therefore there is no intrusion.
    • Technically, since the outer wall temperature is directly related to the temperature inside the house, the thermal camera does give information about what is inside.
  • Why is it that the color of your house is clearly public information, but the temperature of your house is private?
  • Sense enhancing technologies have the potential of reducing the core protection that a home is private, so the Court wanted to draw a sharp line about what was going to be ok as technology increases.
    • It is likely that through the wall technology is coming in the near future.
  • What if, in the future, the general public starts wearing x-ray specs? The court suggests that if something like that happens, then it will no longer be reasonable to assume that your home is private.