By Daniel J. Solove. Solove is the John Marshall Harlan Research Professor of Law and the George Washington University Law School. He is the author of Nothing to Hide: The False Tradeoff Between Privacy and Security (Yale 2011).
The Supreme Court has long held that there is no expectation of privacy in public for the purposes of the Fourth Amendment. Because the Fourth Amendment turns on the existence of a reasonable expectation of privacy, the Court’s logic means that the Fourth Amendment provides no protection to surveillance in public. In United States v. Jones, the Court will confront just how far this logic can extend. FBI agents installed a GPS tracking device on Jones’ car and monitored where he drove for a month without a warrant. 
Jones challenged the warrantless GPS surveillance as a violation of the Fourth Amendment. The D.C. Circuit agreed with Jones. United States v. Jones, 615 F.3d 544 (D.C. Cir. 2010). Other federal circuit courts have reached conflicting conclusions on GPS, and now the Supreme Court will resolve the conflict.
Will the Court revisit its view about the lack of privacy in public given the changing capabilities of technology? Or will it follow its tortured logic to the end, and maintain its wooden and antiquated rule of no expectation of privacy in public?
On its face, the D.C. Circuit opinion appears to clash with the Supreme Court’s decision in United States v. Knotts, 460 U.S. 276 (1983), where the police installed a much simpler tracking device (referred to as a “beeper”) to a person’s car. The Court concluded that the Fourth Amendment did not apply to the beeper because a “person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements.”
The D.C. Circuit distinguished Knotts because the Supreme Court noted in Knotts that the beeper surveillance was limited and explicitly noted that more pervasive surveillance might be treated differently. In concluding that the Fourth Amendment requires a warrant to engage in extensive GPS surveillance, the D.C. Circuit noted that “[w]hen it comes to privacy . . . the whole may be more revealing than the parts.” As the court reasoned:
It is one thing for a passerby to observe or even to follow someone during a single journey as he goes to the market or returns home from work. It is another thing entirely for that stranger to pick up the scent again the next day and the day after that, week in and week out, dogging his prey until he has identified all the places, people, amusements, and chores that make up that person's hitherto private routine.
The Supreme Court will determine if it agrees with this theory.
The problem with the Court’s existing view of no privacy in public is that people often do expect privacy in public. The Court’s conception of privacy wrongly views privacy as total secrecy and fails to recognize that people often have practical obscurity in public.