This GCHQ research report dated 20 September 2011, cowritten by researchers at Heilbronn Institute for Mathematical Research based at the University of Bristol, concerns the use of data mining techniques to develop usable intelligence as well as the contradictions that arise from the use of algorithms to identify wrong doers, or potential wrong doers. The paper also provides a great deal of background information on GCHQ operations and the detailed discussion of network theory demonstrates the power of metadata collection: see the Boing Boing article Doxxing Sherlock, 2 February 2016.
Judge Richard J. Leon’s ruling of 16 December 2013 in the US district court for the District of Columbia concludes that the NSA’s bulk collection of US citizens’ phone metadata likely constitutes “an unreasonable search under the fourth amendement.” This ruling grants an injunction against the collection of the plaintiffs’ metadata, stayed pending appeal.
Less than two weeks after this ruling, Judge William Paley moved to dismiss a similar action brought by the ACLU in the district court of the Southern District of New York. Conflict in the lower courts increases the likelihood that the US Supreme Court will eventually be called upon to adjudicate the issue: see the Guardian article, NSA phone surveillance program likely unconstitutional, federal judge rules, 16 December 2013.