The United States government's innovative use of thermal imaging technology to battle against cultivation and trafficking of marijuana is the center of debate. In United States v. Deaner, the District Court of Pennsylvania and Maryland erred in ruling that the United States government's use of thermal imaging technology in detecting the presence of marijuana and cultivation materials in the home of Tab Deaner was proper and did not violate Deaner's Fourth Amendment right to privacy. The Court affirmed Deaner's constitutional right to a subjective expectation of privacy with respect to heat emanating from his home. The Court compared the facts in United States v. Penny-Feeney where the defendant intentionally used exhaust fans to ventilate heat from his garage. Deaner, however, did not take similar actions and abandon his privacy interest in the emission of heat from his home. Thus, Deaner manifested a subjective expectation of privacy. The Court erred in stating that the degree of technological sophistication of a particular investigative procedure is irrelevant in determining whether the government's use of such technology constituted a search. The use of sophisticated mechanical and electronic detection devices have been held to constitute a search within the meaning of the Fourth Amendment. Failure of the Court to consider the technological capability of a thermal imaging device is contrary to the historical treatment of sophisticated technology in other jurisdictions. The court also erred in failing to recognize the defendant's legitimate expectation of privacy in the heat emanating from his home. The general rule under the plain view doctrine is that the discovery of something through the use of one's natural senses, from a constitutionally permissible vantage point, does not constitute a search within the meaning of the Fourth Amendment. The information recovered by the government's aerial surveillance of Deaner's residence was not information that was in plain view. Aerial reconnaissance of open fields, however, does not constitute a search under this doctrine. The primary exception to this rule is aerial surveillance of the home. The Supreme Court has consistently recognized that individuals have a heightened privacy interest in their home, a constitutionally protected area under the Fourth Amendment. Courts have uniformly held that a warrantless government intrusion into the home constitutes an illegal search within the Fourth Amendment. Finally, the Court erred in ruling that the government's use of thermal imaging for detecting residential heat emissions was valid by analogizing such activity with the use of trained canines to detect drugs. The court failed to recognize several jurisdictions that have specifically held that, under certain circumstances, the use of trained canines to detect drugs is not a constitutionally valid search. The Court's decision is contrary to the protection afforded the public by the express language of the Fourth Amendment. Under a narrow interpretation of this decision, the government is clearly allowed to use thermal imaging to target any individual for surveillance. Under a broad view, the government may be able to use any number of sophisticated surveillance techniques without judicial authorization or review.
Bradley J. Plaschke, United States v. Deaner: Thermal Imagery, the Latest Assault on the Fourth Amendment Right to Privacy, 12 J. Marshall J. Computer & Info. L. 607 (1994)