According to Katz v. United States, what must law enforcement obtain to conduct electronic surveillance?

In Katz v. United States, the Supreme Court established that law enforcement must obtain a warrant to conduct electronic surveillance, especially when it involves the interception of private communications. The ruling emphasized the expectation of privacy that individuals have in their conversations, regardless of the location. This decision expanded the understanding of the Fourth Amendment, which protects citizens from unreasonable searches and seizures.

By requiring a warrant, the court ensured that there is judicial oversight to balance the government’s need for surveillance against individuals’ right to privacy. Obtaining a warrant involves demonstrating probable cause to a judge, thus providing an additional layer of protection for individuals against potential government overreach in their private lives.

The other choices, while they may come into play in certain circumstances, do not fulfill the requirements set out in Katz v. United States for conducting electronic surveillance effectively.