Yesterday, the New Jersey Supreme Court issued a unanimous opinion in the case of State v. Earls, which could have major implications for the way law enforcement uses technology as part of its investigations. Here’s the background, from the New York Times:

The ruling involved a 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.

At trial level, defendant filed a motion to suppress, and though the trial court “found that a defedant had a reasonable expectation of privacy… and that the police should have obtained a warrant”, it still admitted the evidence “under the emergecny aid exception to the warrnat requirement.” The appeals court decided that there was no “reasonable expectation of privacy in his cell-phone location information and that the police lawfully seized evidence in plain view.” Defendant petitioned the state Supreme Court for certification

“limited to the issues of the validity of defendant’s arrest based on law enforcement’s use of information from defendant’s cell phone provider about the general location of the cell phone and the application of the plain view exception to the warrant requirement.”

The court’s opinion is thorough, and includes an entire section that “examin[es] how cell phones function”, but it ultimately concludes that when someone enters into a cellphone contract, they “can reasonably expect that their personal information will remain private.” The court observes that, historically, “the State Constitution [has provided] greater protection against unreasonable searches and seizures than the Fourth Amendment”, before the holding is passed down:

Because of the nature of the intrusion, and the corresponding, legitimate privacy interest at stake, we hold today that 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.

This decision is at odds, the court recognizes, with those of different jurisdictions: Maine and Montana have recently passed laws outlawing wireless tracking, but California’s governor vetoed a bill that would’ve had the same effect. Perhaps the matter is on course for a SCOTUS date sometime soon.