The New York Times has an editorial concerning GPS (a location-tracking technology) and how it affects individual privacy rights.
The Supreme Court has not considered the question of whether the police need a court order to install a GPS device. The government has tried to draw an analogy to a 1983 case in which the court ruled that the police do not need a warrant to use a radio beeper to track a vehicle on public roads, but the circumstances were different. In that case, the police were conducting visual surveillance of a particular suspect’s movements, and a beeper augmented the officers’ senses. A modern GPS device is a far more potent means of tracking people than a beeper.
Lower courts have reached different conclusions. A panel of the Chicago-based United States Court of Appeals for the Seventh Circuit ruled in 2007 that a warrant is not required for remote surveillance by a GPS device, although it said that if the police began to use the technique on a large scale it might violate the Fourth Amendment.
The Times points to People v. Weaver (pdf), a state court case. New York’s highest court held that police needed a warrant to attach a GPS tracker to the suspect’s car and monitor him for more than two months. Chief Judge Jonathan Lippman said:
One need only consider what the police may learn, practically effortlessly, from planting a single device. The whole of a person’s progress through the world, into both public and private spatial spheres, can be charted and recorded over lengthy periods possibly limited only by the need to change the transmitting unit’s batteries. Disclosed in the data retrieved from the transmitting unit, nearly instantaneously with the press of a button on the highly portable receiving unit, will be trips the indisputably private nature of which takes little imagination to conjure: trips to the psychiatrist, the plastic surgeon, the abortion clinic, the AIDS treatment center, the strip club, the criminal defense attorney, the by-the-hour motel, the union meeting, the mosque, synagogue or church, the gay bar and on and on. What the technology yields and records with breathtaking quality and quantity, is a highly detailed profile, not simply of where we go, but by easy inference, of our associations — political, religious, amicable and amorous, to name only a few — and of the pattern of our professional and avocational pursuits.
The ruling is based on the state, not federal, Constitution, so it will apply only in the state of New York. For more, Cornell Law Professor Sherry F. Colb has a great analysis of the case.