Final answer:
SCOTUS's two-part test for a reasonable privacy expectation under the Fourth Amendment includes an individual's actual expectation of privacy and society's recognition of that expectation as reasonable. This concept was articulated in Katz v. United States and refined by the "totality of circumstances" test from Illinois v. Gates.
Step-by-step explanation:
The two-part test developed by the Supreme Court of the United States (SCOTUS) to determine if an expectation of privacy is reasonable under the Fourth Amendment includes: (1) whether the individual has exhibited an actual (subjective) expectation of privacy and (2) whether the expectation is one that society is prepared to recognize as reasonable. This test arose from the landmark case of Katz v. United States, where the court established that the Fourth Amendment's protections extend to all places where an individual has a "reasonable expectation of privacy." To further refine the approach to determining probable cause, subsequent cases such as Illinois v. Gates contributed the "totality of circumstances" test, which evaluates various factors to assess whether a search is justified. These legal precedents illustrate the continuous effort of the judiciary to balance individual rights against the needs of law enforcement in a rapidly evolving technological landscape.