How the Government Justifies Its Data Hauls: The Sieve Theory

By Jane Chong
Wednesday, October 16, 2013, 9:41 AM

What does the government's demand for Lavabit's encryption keys have to do with its justification for its bulk data collection under FISA Section 215? Basic logic. I dub that logic the "sieve theory" of government data filtration, in my latest piece over at the New Republic: Security States (a note to the mathematically inclined: this has nothing to do with sifted sets of integers).

Here's an excerpt explaining the connection:

The sieve theory is kind of the converse of a much-better-understood theory of the Fourth Amendment. The “mosaic theory,” as Fourth Amendment scholar Orin Kerr has dubbed it, has attracted a good deal of attention from scholars interested in the implications of the ever-decreasing costs of perpetual surveillance. That theory posits that many otherwise-insignificant and disparate data points can be combined to yield a highly revealing—and unconstitutionally invasive—composite. For example, in their concurring opinions in the 2012 Supreme Court decision in United States v. Jones, Justices Samuel Alito and Sonia Sotomayor lent credence to the mosaic theory by voicing tentative support for the idea that long-term GPS tracking of a vehicle traveling on public roads could constitute a search, even though the individual units of data were trivial and their acquisition did not meet the traditional definition of a search under Fourth Amendment law.

Like the mosaic theory, the sieve theory is built on the idea that constitutional protections do not attach to information per se but rather hinge on how that information gets processed and used. Just as privacy proponents use the mosaic theory to argue that bits of information not individually entitled to constitutional protections might be entitled to protections when aggregated, the government is effectively using the sieve theory in both the Lavabit and Section 215 contexts to argue that a large data set comprising information to which it might normally not be entitled should be produced anyway where the government both establishes its necessity and institutes satisfactory filters to prevent its misuse.

Put more simply, the mosaic theory has been used to argue the unconstitutionality of certain types of government data collection. Conversely, the sieve theory is being used to argue the lawfulness of carefully conducted government data filtration.