In the United States v. Knotts case of 1982, the U.S. Supreme Court ruled that law enforcement's use of a beeper to track a suspect’s vehicle without obtaining a warrant did not violate the Fourth Amendment rights against unreasonable searches and seizures. The police had placed an electronic tracking device in a container of chloroform purchased by one of Knott's co-conspirators, which was then driven to Knott's secluded cabin where they were manufacturing illicit drugs. The court held that there is no reasonable expectation of privacy for movements on public roads as anyone could observe these actions; thus, using technology like beepers does not constitute an illegal search or seizure under existing laws at that time.

In the dissenting opinion for United States v. Knotts, Justice Brennan argued that the majority's decision failed to adequately consider potential abuses of privacy resulting from technological advancements. He expressed concern about unrestricted police surveillance and warned against a society in which every citizen feels watched by their government. Brennan believed that individuals have a reasonable expectation of privacy while traveling on public roads and this should be protected under the Fourth Amendment, even when technology like beepers are used in tracking movements. He disagreed with the majority’s view that using such devices only provided information officers could obtain through visual surveillance; he emphasized these tools can gather far more data than human senses ever could, thus increasing potential invasions of privacy.