UNITED STATES SUPREME COURT DECISIONS ON-LINE

Having reason to believe that one Armstrong was purchasing chloroform to be used in the manufacture of illicit drugs, Minnesota law enforcement officers arranged with the seller to place a beeper (a radio transmitter) inside a chloroform container that was sold to Armstrong. Officers then followed the car in which the chloroform was placed, maintaining contact by using both visual surveillance and a monitor which received the beeper signals, and ultimately tracing the chloroform, by beeper monitoring alone, to respondent's secluded cabin in Wisconsin. Following three days of intermittent visual surveillance of the cabin, officers secured a search warrant and discovered the chloroform container, and a drug laboratory in the cabin, including chemicals and formulas for producing amphetamine. After his motion to suppress evidence based on the warrantless monitoring of the beeper was denied, respondent was convicted in Federal District Court for conspiring to manufacture controlled substances in violation of 21 U.S.C. § 846. The Court of Appeals reversed, holding that the monitoring of the beeper was prohibited by the Fourth Amendment.

Held: Monitoring the beeper signals did not invade any legitimate expectation of privacy on respondent's part, and thus there was neither a "search" nor a "seizure" within the contemplation of the Fourth Amendment. The beeper surveillance amounted principally to following an automobile on public streets and highways. A person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements. While respondent had the traditional expectation of privacy within a dwelling place insofar as his cabin was concerned, such expectation of privacy would not have extended to the visual observation from public places of the automobile arriving on his premises after leaving a public highway, or to movements of objects such as the chloroform container outside the cabin. The fact that the officers relied not only on visual surveillance, but also on the use of the beeper, does not alter the situation. Nothing in the Fourth Amendment prohibited the police from augmenting their sensory faculties with such enhancement as science and technology afforded them in this case. There is no indication that the beeper was used in any way to reveal information as to the movement of the chloroform container within the cabin, or in any chanroblesvirtualawlibrary

Page 460 U. S. 277

way that would not have been visible to the naked eye from outside the cabin. Pp. 460 U. S. 280-285.

662 F.2d 515, reversed.

REHNQUIST, J., delivered the opinion of the Court, in which BURGER, C.J.,and WHITE, POWELL, and O'CONNOR, JJ., joined. BRENNAN, J., filed an opinion concurring in the judgment, in which MARSHALL, J., joined, post, p. 460 U. S. 285. BLACKMUN, J., filed an opinion concurring in the judgment, in which BRENNAN, MARSHALL, and STEVENS, JJ., joined, post, p. 460 U. S. 287. STEVENS, J., filed an opinion concurring in the judgment, in which BRENNAN, and MARSHALL, JJ., joined, post, p. 460 U. S. 288.