Amid revelations that the National Security Agency and others have monitored Americans’ cell phone calls, a state court has affirmed the privacy rights of cell phone users.

The decision this week by the New Jersey Supreme Court in the case of Thomas W. Earls applies only to residents of the state, but it is being watched as a possible bellwether in the surging dispute over the government’s surveillance powers.

The Electronic Privacy Information Center said the decision is the first to “establish a constitutional right in location data since the U.S. Supreme Court decided United States v. Jones, a GPS tracking case in which several justices expressed concern about the collection of location data.”

In that case, the U.S. Supreme Court ruled police could not attach a tracking device to a suspect’s vehicle and follow him without probable cause and a warrant.

In the Earls case, the court upheld that “individuals have a reasonable expectation of privacy in their cell phone location data.”

According to a state-prepared summary of the decision, police were investigating a burglary ring and identified a suspect.

Officers, without obtaining a warrant, obtained from T-Mobile the location of a cell phone they believed a suspect was using. They ended up arresting that suspect at a motel to which they traced the telephone, with the help of T-Mobile.

But the court found that the New Jersey Constitution protects an individual’s privacy with regard to the location of his or her cell phone. The opinion said “police must obtain a warrant based on a showing of probable cause, or qualify for an exception to the warrant requirement, to obtain tracking information through the use of a cell phone.”

The court ruled that since the officers had not obtained the information about the suspect’s location properly and legally, they were bound not to have access to evidence obtained from the arrest.

“When people make disclosures to phone companies and other providers to use their services, they are not promoting the release of personal information to others,” explains the summary. “Instead, they can reasonably expect that their personal information will remain private. Using a cell phone to determine the location of its owner is akin to using a tracking device and can function as a substitute for 24/7 surveillance without police having to confront the limits of their resources.”

The opinion summary noted that cell phone location data “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.”

As a result of the ruling, a warrant must be obtained after police submit information establishing probable cause to suspect an individual before officers can obtain location data from cell providers.

“Under the plain view doctrine, the state cannot show that the officers were lawfully in the motel room because their presence flowed directly from a warrantless search of T-Mobile’s records.”

The New Jersey Supreme Court said a trial court would have to decide whether the emergency aid doctrine would apply and allow the evidence to be used.

The court opinion said the “data will still be available to law enforcement officers upon a showing of probable cause.”

“To be clear, the police will be able to access cell-phone location data with a properly authorized search warrant. If the state can show that a recognized exception to the warrant requirement applies, such as exigent circumstances, then no warrant is needed.”

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