Subjective and Objective Test
The Fourth Amendment only protects an individual from unreasonable searches and seizures when that individual has an actual and reasonable expectation of privacy in the thing/place being searched or seized. An individual who does not have an expectation of privacy does not have standing to object to the search or seizure.
A court needs to determine first if the individual’s expectation of privacy actually existed. And if it did, then was it reasonable. In essence, there is a subjective and objective test of the expectation.
U.S. Supreme Court Precedent
“My understanding of the rule that has emerged from prior decisions is that there is a twofold requirement, first that a person have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be one that society is prepared to recognize as ‘reasonable.’ Thus a man's home is, for most purposes, a place where he expects privacy, but objects, activities, or statements that he exposes to the ‘plain view’ of outsiders are not ‘protected’ because no intention to keep them to himself has been exhibited. On the other hand, conversations in the open would not be protected against being overheard, for the expectation of privacy under the circumstances would be unreasonable.”
Katz v. United States, 389 U.S. 347, 361 (1967)
“Legitimation of expectations of privacy by law must have a source outside of the Fourth Amendment, either by reference to concepts of real or personal property law or to understandings that are recognized and permitted by society. One of the main rights attaching to property is the right to exclude others, see W. Blackstone, Commentaries, Book 2, ch. 1, and one who owns or lawfully possesses or controls property will in all likelihood have a legitimate expectation of privacy by virtue of this right to exclude. Expectations of privacy protected by the Fourth Amendment, of course, need not be based on a common-law interest in real or personal property, or on the invasion of such an interest.”
Rakas v. Illinois, 439 U.S. 128, 143 (1978)
Subjective vs. Objective
“The central inquiry at this point turns on the concept of lawful possession, and this is where an important qualification of Byrd's proposed rule comes into play. Rakas makes clear that ‘wrongful presence at the scene of a search would not enable a defendant to object to the legality of the search.’. ‘A burglar plying his trade in a summer cabin during the off season,’ for example, ‘may have a thoroughly justified subjective expectation of privacy, but it is not one which the law recognizes as legitimate.’ Likewise, ‘a person present in a stolen automobile at the time of the search may [not] object to the lawfulness of the search of the automobile.’ No matter the degree of possession and control, the car thief would not have a reasonable expectation of privacy in a stolen car.”
Byrd v. United States, 138 S. Ct. 1518, 1529 (2018)
 Katz v. United States, 389 U.S. 347, 361 (1967)
 Byrd v. United States, 138 S. Ct. 1518, 1529 (2018)