What does “expectation of privacy” mean?

Alan Westin’s definition of privacy, as outlined in my last post, is that “Privacy is the claim of individuals, groups, or institutions to determine for themselves when, how, and to what extent information about them is communicated to others.”

That claim can come from multiple sources: a legal regime, a contract, a written privacy statement, a standard industry practice, a custom or a social norm.  It is the last of the sources, unwritten customs or social norms, that lay the foundation for the “expectation” of privacy.  While a written law, contract or statement will clarify the roles and responsibilities of the subject and possessor of the information, the expectation lies in the subject’s belief that a certain social norm governs the actions of the possessor. 

[NOTE: I often use the term subject to refer to the individual or group about whom the information relates and possessor refers to the holder of the information who is contemplating transferring information to a third party.  Possessor can loosely be used, also, to a potential possessor who is contemplating coming into possession of the information in question.]

“Expectation of privacy” is synonymous, in the US, with the 4th Amendment, where one is guaranteed a right to be free from unwarranted invasion of ones “person, houses, papers and effects.”  The purposefully vague language had lead courts to adopt the “reasonable expectation of privacy” standard deferring essentially to ones’ expectation that the government adhere to custom or social norm.   Clearly, tensions arise when there are no customs or social norms or those social norms are in flux or when courts have to analogize to established norms.  See Warshak v. US 6th Circuit 12-14-2010 (stating that there is a reasonable expectation of privacy in email because of its similarity to postal mail and telephonic conversations).