What principle did Katz v. United States establish?

The case of Katz v. United States established the principle that individuals have a subjective expectation of privacy in their communications, specifically in the context of the Fourth Amendment, which protects against unreasonable searches and seizures. In this landmark decision, the Supreme Court ruled that electronic eavesdropping on Katz's phone conversation constituted a search under the Fourth Amendment because Katz exhibited a personal expectation of privacy. This principle is significant because it expanded the interpretation of privacy rights beyond physical spaces to include intangible communications. Without this expectation of privacy, law enforcement could conduct surveillance without warrant, fundamentally altering the balance between personal freedoms and law enforcement powers.

The other options do not accurately reflect the holding of Katz v. United States. The ruling does not state that search warrants are always necessary before any police action or that random surveillance in public places is universally acceptable. Furthermore, the decision does not grant police the ability to bypass the requirement of probable cause based on their subjective feelings of justification. Instead, it solidified the necessity for courts to consider an individual's expectations of privacy when assessing the legality of search and seizure actions.