 Respondent(Knotts) and two codefendants(Darryl Petschen, Tristan Armstrong) were charged with conspiracy to manufacture controlled substances.  The 3M company, which is a manufacturer of chemicals, alerted a narcotics officer working for the Minnesota Bureau of Criminal Apprehension that Armstrong, who was a former 3M employee, had been stealing controlled substances which could be used to manufacture illegal drugs.  Visual surveillance later revealed that Armstrong would purchase similar chemicals from the Hawkins Chemical company in Minneapolis.  Narcotics officers then observed that after the purchase had been made, Armstrong would transport the chemicals to Petschen.  With the consent of the Hawkins company, narcotics officers placed a beeper inside of a five gallon container of chloroform, which was one of the drugs called into question.  The Hawkins company would then place the chloroform that Armstrong purchased in this specific container.

 Officers followed Armstrong after the purchase had been made, maintaining visual surveillance and using a monitor receiving the beeper signals.  Armstrong proceeded to Petschen’s house, where the chemicals were transferred to his car, which police then followed east across the St. Croix river into Wisconsin.  At this time police ended their visual surveillance and the beeper signal was lost, but later picked up an hour later.  The signal was now stationary at a cabin owned by the respondent.  Police then obtained a search warrant and found chemicals and laboratory equipment used to make controlled substances.  The respondent was convicted of conspiring to manufacture controlled substances.  The Court of Appeals ruled the search was unconstitutional.

 Respondent argued that the beeper enabled police to be more effective in detecting crime.  He attacks the use of the beeper to determine the chloroform had come to rest on his property.  He states the government overlooked the fact of using the beeper to determine the chemicals were located on the respondents property, which has the greatest protection under the fourth amendment.

 The movement of Armstrong and Petschen in their cars has no expectation of privacy because all of the movements were on public roads.  Visual surveillance could have viewed the defendants travelling to all of their destinations.  If police had followed Petschen the whole time, they could have viewed him travel to Knotts cabin.  The beeper is simply a more effective way of observing what is already public.  Nothing the obtained from the beeper signal revealed anything about the inside of the cabin or anything that could not have been revealed through visual surveillance.

 The Supreme court of the United States of America ruled that no expectation of privacy was violated and the ruling of the court of appeals was reversed.