460 U.S. 276 (1983)
In 1980, Minnesota law enforcement officers received information from the 3M Company that Tristan Armstrong, a former employee, had been stealing chemicals usable for manufacturing illicit drugs.1 After Armstrong began purchasing similar chemicals from the Hawkins Chemical Company in Minneapolis, officers obtained the company's consent to install a beeper inside a five-gallon container of chloroform.2 When Armstrong purchased the chloroform, officers followed the vehicle using both visual surveillance and signals from the beeper.3
Armstrong delivered the container to codefendant Darryl Petschen at his house.4 Officers then tracked Petschen's automobile as it traveled eastward from Minnesota across the St. Croix River into Wisconsin.5 During the trip, Petschen made evasive maneuvers, causing officers to lose visual contact. Although the beeper signal was temporarily lost, a monitoring device in a helicopter helped relocate it approximately one hour later at a stationary position corresponding to a cabin near Shell Lake, Wisconsin, occupied by respondent Knotts.6
Relying on the beeper-derived location and three days of intermittent visual surveillance of the cabin, officers obtained a search warrant.7 Execution of the warrant revealed a clandestine drug laboratory inside the cabin, along with formulas for amphetamine and methamphetamine, laboratory equipment valued over $10,000, and sufficient chemicals to produce 14 pounds of pure amphetamine.8 The five-gallon chloroform container was found under a barrel outside the cabin.9
Respondent Knotts and Petschen were charged in the United States District Court for the District of Minnesota with conspiracy to manufacture controlled substances in violation of 21 U.S.C. § 846.10 After the district court denied Knotts's motion to suppress evidence obtained from the warrantless monitoring of the beeper, he was convicted and sentenced to five years' imprisonment.11 A divided panel of the United States Court of Appeals for the Eighth Circuit reversed the conviction, and the Supreme Court granted certiorari.12
Whether the warrantless monitoring of a beeper placed inside a container of chloroform and used to track its movement from Minnesota to respondent's cabin in Wisconsin violated respondent's Fourth Amendment rights?13
The Fourth Amendment's reach depends on whether the person invoking its protection can claim a justifiable, reasonable, or legitimate expectation of privacy that has been invaded by government action. This inquiry normally embraces two discrete questions: first, whether the individual by his conduct has exhibited an actual subjective expectation of privacy; second, whether the individual's subjective expectation of privacy is one that society is prepared to recognize as reasonable.14
No. The governmental surveillance conducted by means of the beeper in this case amounted principally to the following of an automobile on public streets and highways.15
A person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another. When Petschen traveled over the public streets he voluntarily conveyed to anyone who wanted to look the fact that he was traveling over particular roads in a particular direction, the fact of whatever stops he made, and the fact of his final destination when he exited from public roads onto private property.16
In the established facts, officers tracked Petschen's automobile as it traveled eastward from Minnesota across the St. Croix River into Wisconsin using both visual surveillance and signals from the beeper after Armstrong delivered the container.17 During the latter part of this journey, Petschen began making evasive maneuvers, and the pursuing agents ended their visual surveillance.18
Respondent Knotts undoubtedly had the traditional expectation of privacy within a dwelling place insofar as the cabin was concerned.19 But no such expectation of privacy extended to the visual observation of Petschen's automobile arriving on his premises after leaving a public highway. Nor did any such expectation extend to movements of objects such as the drum of chloroform outside the cabin in the open fields. Visual surveillance from public places along Petschen's route or adjoining Knotts' premises would have sufficed to reveal all of these facts to the police. 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 the sensory faculties bestowed upon them at birth with such enhancement as science and technology afforded them in this case.20
The warrantless monitoring of the beeper did not invade any legitimate expectation of privacy on respondent's part and therefore constituted neither a search nor a seizure within the contemplation of the Fourth Amendment.21
Related opinions on this issue
Justice Blackmun concurs only in the result reached by the Court.22 The Court's opinion gratuitously refers to the open fields doctrine and twice cites Hester v. United States.23 For him the present case does not concern the open fields doctrine.24 He regards these references and citations as unnecessary for the Court's decision.25
Cases concerning the open fields doctrine have been accepted by the Court for argument and plenary consideration.26 It would be unfortunate to provide either side in these granted cases with support, directly or by implication, for its position.27 He would defer all comments about open fields to a case that concerns that subject and in which the Court has the benefit of briefs and oral argument.28 He therefore does not join the Court's opinion. He concurs only in the result it reaches.29
Joined by Justices Brennan And Marshall
Justice Stevens concurs in the judgment.30 Since the respondent has never questioned the installation of the radio transmitter in the chloroform drum, he agrees that it was entirely reasonable for the police officers to make use of the information received over the airwaves when they were trying to ascertain the ultimate destination of the chloroform.31 He does not join the Court's opinion, however, because it contains two unnecessarily broad dicta.32
First, the Court implies that the chloroform drum was parading in open fields outside of the cabin in a manner tantamount to its public display on the highways.33 The record does not support that implication.34 Second, the Court suggests that the Fourth Amendment does not inhibit the police from augmenting the sensory faculties bestowed upon them at birth with such enhancement as science and technology afforded them.35 The Court held to the contrary in Katz v. United States.36 Although the augmentation in this case was unobjectionable, it by no means follows that the use of electronic detection techniques does not implicate especially sensitive concerns.37