The Right to Quantitative Privacy

Privacy and Security and Innovation and Economic Growth

Article Snapshot


Danielle Citron and David C. Gray


Minnesota Law Review, Vol. 98, No. 1, pp. 62-144, 2013


Law enforcement agencies subject citizens to surveillance by systems that aggregate large amounts of data from sources such as telephone records or drones. Such indiscriminate, broad surveillance violates Fourth Amendment privacy rights.

Policy Relevance

Some technologies can be used for indiscriminate surveillance. Policymakers and courts should limit use of these technologies.

Main Points

  • In 2013, leaks revealed that the Federal Bureau of Investigation (FBI) and the National Security Agency (NSA) analyzed massive amounts of data from phone calls and Internet messages; local police use similar systems.
  • In United States v. Jones, the United States Supreme Court considered whether police use of a GPS-enabled tracking device violated Fourth Amendment privacy rights; at least five Justices stated that citizens can reasonably expect that certain quantities of information about themselves will stay private, a new right of “quantitative” privacy.
  • According to the "mosaic theory" of the Fourth Amendment, the government violates privacy rights when it collects "too much" information in the course of an investigation; this theory is unsatisfying.
  • Courts should recognize that the Fourth Amendment should limit law enforcement's use of a technology if the technology could facilitate broad, indiscriminate surveillance, raising the specter of a surveillance state.
  • Drones threaten to enable indiscriminate surveillance, providing a constant stream of information about everyone within view at low cost.
    • As with wiretaps, police should use drones only as authorized by law and under supervision by a court.
    • Courts should require police to show probable cause that a drone will produce evidence relating to a specific investigation.
    • Surveillance by human agents differs, being too costly to be conducted on a large scale.
  • Data mining threatens expectations of quantitative privacy, and law enforcement agencies should seek agreement with advocacy and interest groups to limit the scope of data mining.
  • If unfettered data mining and surveillance programs are permitted by the Foreign Intelligence Surveillance Act (FISA), courts should recognize that FISA itself is unconstitutional.

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