Unwarranted Intrusion: GPS and the Fourth Amendment

In a four-to-three decision last week, New York's highest court rejected the use of global positioning system (GPS) technology by law enforcement to secretly track an individual's movements without first obtaining a warrant. Over the past several years, GPS technology has become an increasingly ubiquitous convenience. As the technology's prevalence and utility grows, however, the potential for its abuse raises important and delicate questions of constitutional law that remain largely unsettled.

With its decision, the New York Court of Appeals joins the Washington Supreme Court in concluding that government GPS tracking requires a warrant. A number of courts, however, have reached the opposite conclusion. In the most prominent case to yet address the issue, Judge Posner wrote for the Seventh Circuit in United States v. Garcia that the tactic did not in itself trigger the warrant protections of the Fourth Amendment.

Judge Posner's reasoning on this issue unfortunately was based on his interpretation of the Supreme Court's decision in United States v. Knotts, which permitted police to use simple "beeper" technology without a warrant when tracking a single suspect's movements. Knotts, however, is of limited value here. First, the court acknowledged that in the event that "dragnet-type" twenty-four hour surveillance were to become a reality, "different constitutional principles may be applicable." Second, the technology addressed in Knotts simply isn't analogous to the capabilities of GPS. Whereas beeper technology "augmented" officers' own visual observations, GPS technology provides a complete and superior substitute for physical tracking. In more recent decisions, the Court has indicated that similarly sophisticated techniques such as thermal imaging and satellite surveillance technologies require a warrant.

For his part, Judge Posner didn't rule out that GPS tracking may require a warrant in the event that it's applied on a "mass" basis. But such a distinction wrongly suggests that the Fourth Amendment affords less privacy protection to individuals than to victims on a mass scale.

Two issues govern whether a warrant is required under the Fourth Amendment: (1) whether the government has intruded into a matter as to which an individual has exhibited an actual expectation of privacy; and (2) whether the individual's expectation of privacy is one that society is prepared to recognize as reasonable. The question of whether GPS technology satisfies these criteria is presently before the D.C. Circuit, and I recently joined a group of lawyers on behalf of the American Civil Liberties Union (ACLU) and the Electronic Frontier Foundation (EFF) to encourage the court to adopt an analysis that recognizes the bold realities of GPS surveillance and the public's reasonable expectation of not being subject to its powerful tracking around the clock.

GPS receivers calculate latitude, longitude, altitude, direction and speed by receiving and processing location information from the transmissions of the four nearest GPS satellites in orbit. Apart from being increasingly accurate and powerful, the technology is now so commonplace and the devices so miniature that the tagging and tracking of large masses can now be accomplished with little effort.

In one ripped-from-the-comic-books example, the Los Angeles Police Department has begun outfitting its cruisers with air guns capable of launching GPS-enabled "darts" at passing cars. The darts adhere to their targets, and thereafter permit remote, real-time tracking of the vehicle from L.A. police headquarters. I confess, it sounds pretty neat. And applied properly, it is truly exciting to see law enforcement make impressive use of these emerging capabilities. But technological advancements cannot excuse the fundamental protections of the Constitution.

Absent a warrant requirement, the police could track unlimited numbers of citizens for months at a time, without ever leaving their desks. No person with a GPS-enabled cell phone could be confident that she was free from round-the-clock surveillance by a network of satellites logging her past movements with utmost precision, even potentially noting the time and location that she crossed paths with other GPS-tracked individuals.

This surveillance also implicates our First Amendment rights to associate privately with others. In NAACP v. Alabama, the Supreme Court held that a court could not compel the NAACP to produce its membership list because the First Amendment protects "freedom to associate and privacy in one's associations." By the same token, GPS tracking can reveal whether a person associates with a particular religious organization, visits a Planned Parenthood clinic, or attends a meeting of an unpopular political organization - information that is just as revealing as a membership list. The Supreme Court has also emphasized that the warrant requirement should be "scrupulously observed" when First Amendment concerns are presented.

While the reasonable expectation of privacy is certainly an evolving standard, the time has come to recognize that government GPS tracking offends this expectation. Although a number of empirical studies support this proposition, it doesn't require scientific evidence to understand that the "Big Brother" of Orwell's 1984 retains its emotive power precisely because people expect that they enjoy freedom from extensive technological tracking by the government.

GPS technology presents a very powerful and exciting tool for law enforcement in this country. But, as Judge Posner himself aptly recognized in Garcia, "the meaning of a Fourth Amendment search must change to keep pace with the march of science."