United States V. KNOTTS

This is an audio case brief of United States v. Knotts, 460 U.S. 276 (1983). The audio brief provides a full case analysis. However a written summary of the case is provided below.

Table of Contents


The 3M Company, which manufactures chemicals in St. Paul, notified a narcotics investigator for the Minnesota Bureau of Criminal Apprehension that Armstrong, a former 3M employee, had been stealing chemicals which could be used in manufacturing illicit drugs. Visual surveillance of Armstrong revealed that after leaving the employ of the 3M Company, he had been purchasing similar chemicals from the Hawkins Chemical Company in Minneapolis. The Minnesota narcotics officers observed that after Armstrong had made a purchase, he would deliver the chemicals to codefendant Petschen.

With the consent of the Hawkins Chemical Company, officers installed a beeper inside a five gallon container of chloroform, one of the so-called “precursor” chemicals used to manufacture illicit drugs. Hawkins agreed that when Armstrong next purchased chloroform, the chloroform would be placed in this particular container. When Armstrong made the purchase, officers followed the car in which the chloroform had been placed. The officers maintained contact by using both visual surveillance and a monitor which received the signals sent from the beeper.

Armstrong proceeded to Petschen’s house, where the container was transferred to Petschen’s automobile. Officers then followed that vehicle eastward towards the state line, and into Wisconsin. During the latter part of this journey, Petschen began making evasive maneuvers, and the pursuing agents ended their visual surveillance. At about the same time officers lost the signal from the beeper, but with the assistance of a monitoring device located in a helicopter the approximate location of the signal was picked up again about one hour later. The signal now was stationary and the location identified was a cabin occupied by Knott near Shell Lake, Wisconsin. The record did not reveal that the beeper was used after the location in the area of the cabin had been initially determined.

Relying on the location of the chloroform derived through the use of the beeper and additional information obtained during three days of intermittent visual surveillance of Knott’s cabin, officers secured a search warrant. During execution of the warrant, officers discovered a fully operable, clandestine drug laboratory in the cabin. In the laboratory area officers found formulas for amphetamine and methamphetamine, over $10,000 worth of laboratory equipment, and chemicals in quantities sufficient to produce 14 pounds of pure amphetamine. Under a barrel outside the cabin, officers located the five gallon container of chloroform.

After his motion to suppress evidence based on the warrantless monitoring of the beeper was denied, Knott was convicted for conspiring to manufacture controlled substances in violation of 21 U.S.C. § 846 (1976). He was sentenced to five years imprisonment.

The United States Court of Appeals for the Eighth Circuit reversed the conviction. That court found that the monitoring of the beeper was prohibited by the Fourth Amendment because its use had violated Knott’s reasonable expectation of privacy.

The U.S. Supreme Court agreed to review the case.


Whether a beeper which was placed in a drum containing chloroform, and  which allowed law enforcement officers to trace the location of the can of chloroform violated the Fourth Amendment to the United States Constitution.


One has a lesser expectation of privacy in a motor vehicle because its function is transportation and it seldom serves as one’s residence or as the repository of personal effects. A car has little capacity for escaping public scrutiny. It travels public thoroughfares where both its occupants and its contents are in plain view


The court begun its analysis by laying down Katz reasonable expectation of privacy test. The Katz reasonable expectations of privacy requires that an individual, by his conduct, has exhibited an actual (subjective) expectation of privacy, and  the individual’s subjective expectation of privacy is one that society is prepared to recognize as reasonable.

The court explained that an induvial expectation of privacy is diminished when inside a motor vehicle traveling through public roads.

The court stated that:

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.

We have commented more than once on the diminished expectation of privacy in an automobile: One has a lesser expectation of privacy in a motor vehicle.

A person travelling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another. When Petschen travelled over the public streets he voluntarily conveyed to anyone who wanted to look the fact that he was travelling over particular roads in a particular direction. He also conveyed the fact of whatever stops he made, and the fact of his final destination when he exited from public roads onto private property.

Knotts, as the owner of the cabin and surrounding premises to which Petschen drove, undoubtedly had the traditional expectation of privacy within a dwelling place insofar as the cabin was concerned. But no such expectation of privacy extended to the visual observation of Petschen’s automobile arriving on his premises after leaving a public highway. Petchen neither had an expectation of privacy 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 in this case relied not only on visual surveillance, but on the use of the beeper to signal the presence of Petschen’s automobile to the police receiver, 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.


The court held that officers monitoring the beeper signals did not invade any legitimate expectation of privacy on his part. Therefore there neither a search or seizure within the meaning of the fourth amendment.

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