On Nov. 29, 2017, the United States Supreme Court heard arguments in a case in which the police had, over a period of 127 days, collected petitioner's location from signals given off by his cell phone. (Carpenter v. United States). This was done without a search warrant and resulted in Carpenter being arrested in connection with a number of armed robberies which had occurred in the states of Michigan and Ohio. The court is now considering whether, when the government seeks to track what are referred to as digital footprints, it must first obtain a search warrant based upon probable cause.

The justices appear to be divided in their views of this matter. The threshold question is what does the Fourth Amendment protect. Supreme Court precedent would suggest that a search occurs where an individual's objective expectation of privacy is violated. Thus, some contend that when a person uses a cell phone, he or she must know or be presumed to know that sending or receiving messages on a cell phone is in the public domain and thus not protected by the Fourth Amendment. To state the matter differently, under what is referred to as the “third-party doctrine,” a person has no reasonable expectation of privacy and information voluntarily surrendered to third parties such as internet providers and banks. On the other hand, some contend that to collect location information without a warrant flies in the face of long-standing expectations that, in the words of counsel for the petitioner in the Carpenter case, “. . . the collection of this information is a search, as it disturbs people's long-standing practical expectation that their longer-term movements in public and private spaces will remain private.”

It is difficult to predict the outcome of this case, given the diverse views expressed by the justices during the argument. The court may adopt the position of the government and hold that the Fourth Amendment was not violated and that a warrant was unnecessary. However, we in New Jersey will recall that our Supreme Court, in the case of State v. Thomas W. Earls (A-53-11), decided four years ago, that article I, paragraph 7 of the New Jersey Constitution “. . . protects an individual's privacy interest in the location of his or her cell phone.”  The police in our state must obtain a warrant based on a showing of probable cause to obtain tracking information, unless an exception to the warrant requirement can be demonstrated. In short, the New Jersey Constitution “. . . provides greater protection against unreasonable searches and seizures that in the Fourth Amendment.”  (Earles, supra). The United States Supreme Court should follow the lead of New Jersey, hold that a subpoena is required, and review the scope of the third-party rule.