On Nov. 8, 2011, the U.S. Supreme Court will hear argument in United States v. Jones, to determine whether the government violates the Fourth Amendment when it affixes a Global Positioning System (GPS) tracking device to a person’s car and monitors its movements on public streets for four weeks without a warrant.

In determining whether a search occurred, two views of an individual’s expectation of privacy are at odds:

  1. The driver has no reasonable expectation of privacy for any such movements because he is voluntarily exposing his route information to the public.
  2. Though the individual trips are voluntarily exposed to the public, the overall pattern of movement during four weeks is not so exposed because the likelihood anyone will observe all the trips is “effectively nil.” When it comes to an expectation of privacy, can the whole be greater than the sum of the parts?

Antoine Jones was thought to be involved in a conspiracy to distribute cocaine. Law enforcement obtained a warrant to install and monitor a GPS tracking device on Jones’s car. The warrant authorized installation within 10 days and only in the District of Columbia. Instead, the agents installed the GPS device 11 days later in a public parking lot in Maryland. Jones’s car was tracked in the vicinity of a suspected stash house where cocaine, large amounts of cash and various drug processing and packaging items were later found. Jones moved to suppress the GPS tracking data. The district court granted the motion in part and only admitted the tracking data from locations on public streets. Jones was convicted of conspiracy to distribute cocaine.

On appeal, the U.S. Court of Appeals for the D.C. Circuit reversed Jones’s conviction because it was obtained with evidence procured in a warrantless search, a violation of the Fourth Amendment. The D.C. Circuit found the key issue to be whether use of the GPS device violated Jones’s reasonable expectation of privacy. The Supreme Court had previously held that “[a] person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another.” United States v. Knotts, 460 U.S. 276, 281 (1983). In Knotts, police had followed a car having a container holding a beeper therein, which allowed the police to reestablish contact when they lost visual surveillance on a single, 100-mile trip. In the D.C. Circuit’s view, Knotts was limited to a short surveillance and had reserved the question of the outcome for a prolonged surveillance. The D.C. Circuit acknowledged both the 7th and 9th Circuits had relied on Knotts in holding that prolonged use of a GPS device was not a search. According to the D.C. Circuit, in those cases, neither accused challenged Knotts as controlling.

The D.C. Circuit held that the totality of Jones’s movements was not exposed to the public for two reasons:

  1. Unlike movements during a single journey, the whole of a person’s movements over the course of a month is not actually exposed to the public because the likelihood anyone will observe all those movements is effectively nil.
  2. The whole of movements is not exposed constructively even though each individual movement is exposed, because that whole reveals more — sometimes a great deal more — than does the sum of its parts.

Under this “mosaic” theory, the D.C. Circuit held that Jones had a reasonable expectation of privacy in the totality of his month-long pattern of movements. Thus, the government’s tracking of those movements constituted a search conducted without a warrant. Therefore, the D.C. Circuit reversed Jones’s conviction.

In the Supreme Court, the U.S.  argues that Knotts has already  held that use of technology to enhance police’s ability to acquire information in the public domain is not a search. The government further argues that the important factor is not the “likelihood” anyone would acquire all of the information, but rather whether the information “could have” been acquired if an individual so desired. In addition, the mosaic theory has no basis as “the sum of an infinite number of zero-value parts is also zero.” The U.S. argues that both the “likelihood” of acquisition and the mosaic theory are unworkable and provide no meaningful guidance to law enforcement as to when GPS tracking becomes a search.

In response, Jones says installing and using a GPS device to track an individual’s movements is a search regardless of how long the tracking lasts. Jones argues that GPS tracking data is involuntarily exposed to the naked eye. If the Supreme Court desires a bright line rule, it could hold that GPS tracking longer than one day is a search.

It remains to be seen what the Supreme Court will say about an expectation of privacy in relation to warrantless GPS tracking. The Supreme Court’s views on the expectation of privacy in United States v. Jones may inform us as to how the court would address other privacy issues in the digital age.