For the last 40 years, the hornbook law of what amounts to a Fourth Amendment search was that a search occurs when government conduct violates both a subjective expectation of privacy and an objective reasonable expectation of privacy. As of this morning’s decision in Jones, the new doctrine for what is a Fourth Amendment “search” appears to be as follows:
A search occurs either when
(a) A trespassory test is satisfied: (1) a “trespass” occurs, (2) the trespass is onto an enumerated item listed in the Fourth Amendment (“persons, houses, papers, or effects”), and (3) it occurs with the intent “to find something or to obtain information”
(b) The Katz test is satisfied: the government conduct violates a subjective expectation of privacy and an objective reasonable expectation of privacy
Today’s majority opinion in Jones announces the trespassory test and applies to to find that the installation of the device with intent to use it was a search. As a result, the Court doesn’t purport to reach the “reasonable expectation of privacy” question. The Court also did not reach when installing a GPS device is a reasonable search, holding that the issue was forfeited because it was not raised below.
UPDATE: At first blush, one question I’m not entirely certain of is what the test is for a trespass. Trespass law has changed over time, and it varies state to state. Civil trespass can be different from criminal trespass. Is the question whether the act would have constituted a trespass at common law, or whether it is a trespass today? Justice Alito’s opinion indicates that he thinks the test is a trespass at common law, but does the majority take a view on that?