## Facts

- Minnesota law enforcement suspected Tristan Armstrong of obtaining chemicals to manufacture illicit drugs.
- Officers arranged for a chemical supplier to place a radio transmitter (“beeper”) inside a chloroform container sold to Armstrong.
- After the purchase, the container was placed in a vehicle; officers followed the vehicle using a combination of visual surveillance and beeper monitoring.
- Officers ultimately traced the chloroform to Leroy Carlton Knotts’s secluded cabin in Wisconsin, at points relying on beeper monitoring alone to maintain contact.
- Police conducted three days of intermittent visual surveillance of the cabin, then obtained a search warrant.
- The warranted search uncovered the chloroform container and a drug laboratory with chemicals and formulas for producing amphetamine.
- Knotts was charged and convicted in federal court of conspiracy to manufacture controlled substances under 21 U.S.C. § 846, based largely on evidence developed after the beeper-assisted tracking and the warrant search.
- The district court denied Knotts’s motion to suppress; the Eighth Circuit reversed, holding the beeper monitoring violated the Fourth Amendment.

## Issues

1. Whether warrantless monitoring of a beeper placed in a container, used to track the container’s movement by automobile on public roads to Knotts’s cabin, constituted a Fourth Amendment “search” or “seizure” requiring a warrant.

## Decision

- The Supreme Court reversed the Eighth Circuit and reinstated the conviction.
- Monitoring the beeper signals, as used here to track movements on public thoroughfares and to locate the destination, did not invade a legitimate expectation of privacy.
- Because there was no legitimate expectation of privacy in the movements monitored, the beeper monitoring was neither a “search” nor a “seizure” under the Fourth Amendment.
- The Court emphasized the record showed no use of the beeper to reveal information about movements of the container inside the cabin.
- Concurring Justices agreed with the result but expressed reservations about the constitutional footing of the beeper’s placement and about the majority’s broader doctrinal discussion.

## Legal Principles

- A person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in movements from one place to another.
- Police may use technology to augment sensory perception when it only facilitates observation of information otherwise obtainable through lawful visual surveillance.
- The heightened expectation of privacy in a dwelling does not, without more, extend to beeper-assisted tracking that reveals only that an object arrived at premises and does not disclose information about activities inside the home.
- The constitutionality of more intensive, automated, or continuous location tracking was left open for future cases on different facts.

## Conclusion

Warrantless beeper monitoring used to follow a container’s single trip over public roads to a suspect’s cabin, without revealing information about activity inside the home, does not constitute a Fourth Amendment search or seizure; evidence obtained pursuant to a subsequent warrant was therefore admissible.


United States v. Knotts, 460 U.S. 276 (1983)