Over on Concurring Opinions, Kyle Graham has posted an interesting analysis of how the phrase “reasonable expectation of privacy” (REP) has been popularized since Katz v. United States. Specifically, Graham tabulated the number of cases in Westlaw ALLCASES that cited Katz through 2009 and looked at what percentage of them included the phrase “reasonable expectation of privacy.”
Somewhat curiously, the findings depict a nonmonotonic trend over the years, with a recent decline in the relative use of the phrase even though Katz continues to be cited frequently. In 2009, for example, Katz was cited in 392 cases – more than any previous year in the sample – but REP was cited in less than 40% of those instances, whereas in the 1980’s, over half the cases citing Katz mentioned REP.
You can read Kyle’s analysis and the comments on it here.
As to what it all means, well, I don’t think there’s any conclusion we can draw from the data at this point, but it is curious, to say the least.