What is the significance of the case "Katz v. United States"?

The case "Katz v. United States" is significant because it established the principle of "reasonable expectation of privacy," which is a crucial aspect of Fourth Amendment protections. In this landmark decision, the U.S. Supreme Court determined that individuals have a reasonable expectation of privacy in their telephone conversations, even when they are in a public domain. The case arose when federal agents used a listening device to overhear Katz’s conversations without obtaining a warrant. The Court ruled that this action violated Katz’s Fourth Amendment rights, thus expanding the interpretation of what constitutes a "search" under the amendment.

This ruling is foundational because it shifts the focus from the physical intrusion of property to the expectation of privacy, influencing many subsequent rulings involving technology and privacy rights. The development of this standard has profound implications in modern jurisprudence, impacting how courts view privacy in various contexts, including digital communication and electronic surveillance.