In the United States v. Karo et al., 1983, the Supreme Court ruled that government installation of a tracking device in a can of ether did not constitute an illegal search under the Fourth Amendment. However, it held that monitoring said device without a warrant when it was inside private residences violated privacy rights protected by this amendment. The case involved federal agents replacing one out of ten cans of ether (used to extract cocaine from clothing) with their own containing a radio transmitter which allowed them to track its location and movement. While they had obtained consent from the original owner for installing this device, they did not have warrants for subsequent surveillance activities within private properties where these cans ended up being stored or used.

In the dissenting opinion for United States v. Karo et al., Justice O'Connor, joined by Justices Brennan and Marshall, argued that a warrantless installation of a tracking device constituted an invasion of privacy and violated the Fourth Amendment rights against unreasonable searches and seizures. The dissenters contended that even though the initial transfer of the can containing the beeper was legal, it did not justify subsequent monitoring without a warrant. They believed that this case represented an intrusion into private premises which required explicit judicial approval via a search warrant to ensure protection from arbitrary government surveillance. Furthermore, they disagreed with majority's distinction between visual surveillance from public places versus electronic monitoring within private homes or offices - asserting both should require warrants due to their invasive nature.