United States v. Knotts

Police investigating chemical thefts learned Tristan Armstrong (defendant) was buying chemicals used to make drugs and delivering them to Darryl Petschen (defendant). With the seller's consent, police placed a radio beeper inside a chloroform container given to Armstrong and used it, along with visual surveillance, to follow the container to Knotts's (defendant) Wisconsin cabin, where a subsequent search warrant revealed a drug lab. Knotts moved to suppress the beeper evidence as a warrantless Fourth Amendment violation.