To get at why I would ask this question in the first place, some background on the Fourth Amendment may be helpful.
Katz v. United States is the decision at the foundation of most modern Fourth Amendment doctrine. There, the Supreme Court held that FBI agents carried out a search under the Fourth Amendment when they used a listening device to record a conversation that the defendant was having in a glass phone booth. Noting that "the Fourth Amendment protects people, not places," the Court held that Fourth Amendment protection from unreasonable searches was not defined by whether a person was in a constitutionally-protected location.
Justice Harlan concurred, and enunciated a test for determining whether the government engages in a "search" under the Fourth Amendment:
[T]here 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."
This test has become the foundation for determining whether government agents engage in a search in most situations (although United States v. Jones reminds us that common-law trespass on property specified in the Fourth Amendment is still an important inquiry).
Typically, the question courts must answer is whether an individual has a "reasonable" expectation of privacy. While individuals may think that they are deserving of privacy, their expectation may not be one society is prepared to recognize as reasonable. For instance, two people engaging in a loud conversation in a coffee shop may think that their conversation is private, but this may not be a reasonable expectation if everybody sitting around them can hear what is being said.
But what of the first prong of the test -- whether a person exhibits an actual or subjective expectation of privacy? Say that somebody (incorrectly) believes that the government is always listening to and recording his telephone conversations. So one day when the government actually does record one of his conversations, that person subjectively believes that the government is listening, even though Katz indicates that it is reasonable to expect one's telephone conversations to be private. Would this paranoid person's conversation be protected by the Fourth Amendment?
I learned of the answer today from Josh Blackman's fascinating discussion of the drafting of Smith v. Maryland, the case that is typically recognized (and criticized) for establishing the modern third-party doctrine - that people do not have a reasonable expectation of privacy in information knowingly turned over to third parties. Blackman discusses Justice Stevens's push to include a footnote in the final opinion, and his joining in the opinion after the footnote's inclusion. That footnote (footnote five) reads:
Situations can be imagined, of course, in which Katz’ two-pronged inquiry would provide an inadequate index of Fourth Amendment protection. For example, if the Government were suddenly to announce on nationwide television that all homes henceforth would be subject to warrantless entry, individuals thereafter might not in fact entertain any actual expectation of privacy regarding their homes, papers, and effects. Similarly, if a refugee from a totalitarian country, unaware of this Nation’s traditions, erroneously assumed that police were continuously monitoring his telephone conversations, a subjective expectation of privacy regarding the contents of his calls might be lacking as well. In such circumstances, where an individual’s subjective expectations had been “conditioned” by influences alien to well-recognized Fourth Amendment freedoms, those subjective expectations obviously could play no meaningful role in ascertaining what the scope of Fourth Amendment protection was. In determining whether a “legitimate expectation of privacy” existed in such cases, a normative inquiry would be proper.The second hypothetical in this example answers the question I pose in this post: even if an individual does not have a subjective expectation of privacy, if that expectation of no-privacy is the result of "influences alien to well-recognized Fourth Amendment freedoms," then it does not matter that the individual does not have a subjective expectation of privacy.
The answer is still a bit vague, since it might not be clear what work "well-recognized Fourth Amendment freedoms" is doing. Blackman's post includes correspondence from Justice Stevens that indicates that a subjective expectation of privacy is "most important" when the Court is:
[E]valuating a claim that Fourth Amendment protection should be extended into a new area--wiretap in Katz and pen registers here--but would not be relevant in situations, such as house searches, where Fourth Amendment protection is well recognized in our decided cases.So it would seem that the paranoid person who thinks the government is listening to all of his telephone conversations still gets Fourth Amendment protections. But a paranoid person who thinks the government is intruding into an area that is not an established, protected area (say, an unsecured wireless network) may end up losing Fourth Amendment protection because he lacks a subjective expectation of privacy.