[JURIST] The US Court of Appeals for the District of Columbia Circuit [official website] ruled [opinion, PDF] Friday that prolonged use of global positioning systems (GPS) to monitor suspects’ vehicles violates the Fourth Amendment [text] protection against unreasonable searches and seizures. The appellate court found that there exists a reasonable expectation of privacy in the “whole of a person’s movements over the course of a month” because the combination of all such movements is not actually or constructively exposed to the public. Although the Supreme Court’s ruling in United States v. Knotts [opinion text] allows the use of tracking devices to follow vehicles from one place to another based on a lower expectation of privacy on public roads, the appeals court distinguished the instant case by finding that too much personal information is revealed over longer periods of time. The court discussed the expectations of society, stating:

Society recognizes Jones’s expectation of privacy in his movements over the course of a month as reasonable, and the use of the GPS device to monitor those movements defeated that reasonable expectation. As we have discussed, prolonged GPS monitoring reveals an intimate picture of the subject’s life that he expects no one to have — short perhaps of his spouse.

The decision adds to a split among appellate courts on the issue, although the court noted that decisions to the contrary “were not alert to the distinction … between short-term and prolonged surveillance” in the relevant precedent.

In June, the US Supreme Court unanimously held [opinion, PDF; JURIST report] that, even if there is a reasonable expectation of privacy in work-issued electronic devices, that an employer’s search of private text messages does not violate the Fourth Amendment so long as the search is not excessive and is pursuant to a legitimate work-related purpose. In February, the US Court of Appeals for the Ninth Circuit ruled [opinion, PDF; JURIST report] that strip searching all incoming inmates does not violate the Fourth Amendment because it is necessary in order to prevent illegal substances from entering prisons.