Your cell phone is constantly pinging cell towers, registering your location, and long-term monitoring of this cell-site data provides a very detailed snapshot of your movements and of your private life. The government believes you don't own that information, your wireless carrier does, and since a third party stores your records, you have no reasonable expectation of privacy.

With warrantless GPS tracking no longer legal, the government is going after Jones again and is gung-ho to use warrantless cell phone locational tracking via historical cell tower location records. Eduardo Balarezo, Jones' attorney, wrote, "In this case, the government seeks to do with cell site data what it cannot do with the suppressed GPS data." But in the motion to suppress, Balarezo argued this type of prolonged monitoring violates Jones' expectation of privacy. "The government obtained the cell site data in violation of the Fourth Amendment to the United States Constitution and therefore it must be suppressed."

On January 23, 2012, in the biggest Fourth Amendment and privacy case in the digital age, the U.S. Supreme Court ruled in U.S. v. Jones [PDF] that the government violated the Fourth Amendment and unanimously agreed that police needed probable cause and a search warrant before planting a GPS tracking device to an American's vehicle. Since GPS tracking evidence helped to convict drug dealer Antoine Jones, his life sentence was tossed out. Since then, the FBI has turned off about 3,000 GPS tracking devices. But now government prosecutors are seeking to retry Jones and said the GPS information is not needed; historical cell-site tower data provides locational tracking that can be used to map Jones' movements, activities and contacts. The cell-data was not used in either of the two previous trials against Jones.

Balarezo pointed out that "electronic surveillance of an individual's location as he travels in public has traditionally not been construed as a Fourth Amendment search, although electronic surveillance of his location within his home has been." According to court papers filed late Thursday, "The Supreme Court in Katz v. United States set forth a two part standard for when a Fourth Amendment search has occurred: (1) the individual has 'manifested a subjective expectation of privacy' in the thing searched; and (2) 'society is willing to recognize that expectation as reasonable'."

The Supreme Court ruled that:

Mr. Jones did have a reasonable expectation of privacy over the totality of his movements over the course of a month. The court reasoned that the totality of one's movements over an extended time period is not actually exposed to the public "because the likelihood a stranger would observe all those movements is not just remote, it is essentially nil."... The court concluded that people have an objectively reasonable expectation of privacy in the totality of their movements over an extended period because an individual's privacy interests in the totality of his movements far exceeds any privacy interest in a single public trip from one place to another.

So we're back to the question, Do you give up a reasonable expectation of privacy by carrying a cell phone?

According to the government [PDF], A cell phone customer "has no reasonable expectation of privacy in cell-site information" and has "no Fourth Amendment privacy interest in business records created and held by a third party." Instead, those historical cell-site records "are the phone company's business records rather than a customer's private papers." The government says that people are aware of this tracking capability and anyone arguing otherwise "relies too heavily on cell-phone users remaining unaware of the capacities of cellular technology, a doubtful proposition in the first place."

Regarding the Jones' case, the government "also sought authorization for a pen register, trap and trace and caller identification device."