The New Jersey Supreme Court ruled that cell owners can “reasonably expect that their personal information will remain private” and in order to get GPS location data police must get a search warrant. The question in State v. Thomas W. Earls was the “constitutional right to privacy in cell-phone location” and the unanimous decision written by Chief Justice Stuart Rabner included the following:
Using a cellphone to determine the location of its owner can be far more revealing than acquiring toll billing, bank, or Internet subscriber records,...
Details about the location of a cellphone can provide an intimate picture of one’s daily life and reveal not just where people go — which doctors, religious services and stores they visit — but also the people and groups they choose to affiliate with. That information cuts across a broad range of personal ties with family, friends, political groups, health care providers and others.
The New York Times reported that no search warrant was secured by police in the case:
...that began with a string of burglaries in homes in Middletown, N.J. A court ordered the tracing of a cellphone that had been stolen from one home, which led to a man in a bar in nearby Asbury Park, who said his cousin had sold him the phone, and had been involved in burglaries. The police then used data they got from T-Mobile to locate the suspect, Thomas W. Earls, at three points on a subsequent evening, tracking him to a motel room where he was found with a television and suitcases full of stolen goods.
In part the New Jersey Supreme Court relied on the 2012 US Supreme Court decision of US v. Jones which required a search warrant for police to add a GPS device to a suspect’s automobile.
Given the current headlines about privacy disclosures, it is debateable about whether search warrants for GPS location data will continue to be the law.