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The National Security Agency has admitted to collecting bulk records of U.S. phone traffic, but the agency says it does not currently track the location of cellphones. The NSA has said it would be legal to collect that information, and law enforcement agencies across the country do subpoena such data on a regular basis.
That's led to a movement to protect cellphone location information. NPR's Larry Abramson reports that civil liberties groups hope it will lead to tougher rules for all government surveillance.
LARRY ABRAMSON, BYLINE: First, some basics. You probably know - or should know - that your cellphone is tracking your location wherever you go. Professor Matt Blaze, of the University of Pennsylvania, says that's just how the cell system operates.
MATT BLAZE: As you move around, your phone is constantly checking to see whether the tower that it's currently registered with is the best one, or if there's a better tower with a stronger signal coming in range.
ABRAMSON: Cellphone companies store that information so they can deliver better service. That's handy for the police. The Suffolk County, Mass., district attorney regularly asks phone companies for that information, according to spokesman Jake Wark.
JAKE WARK: They're a part of almost every major case including homicide; in some cases, sexual assault; drug-trafficking cases.
ABRAMSON: And one cellphone search, in particular, could serve as a test case for civil liberties groups who are challenging law enforcement access to such information. Shabazz Augustine stands accused of murdering a former girlfriend nine years ago, and state prosecutors want to use information that they got about the location of his cellphone at the time.
The ACLU's Matt Segal told the state's high court that evidence should be thrown out because police got it using a simple subpoena, not a search warrant.
MATT SEGAL: All the government has to show is that the information they're requesting is relevant and material to an ongoing investigation.
ABRAMSON: That standard is too low, Segal says, and it encourages searches before a crime is committed - like the collection of nearly all the nation's phone traffic by the National Security Agency. The government relies on that same relevance standard to justify collecting bulk phone records.
Now, groups like the ACLU are arguing in court that widespread use of cell location information shows that digital information needs stronger protections. Matt Segal says it should only be released when it meets a higher standard; probable cause, to show someone has committed a crime.
SEGAL: When we do this case, what we're focused on is the possibility that governments are obtaining this kind of location information on many people who have not committed crimes.
ABRAMSON: The New Jersey Supreme Court has already backed the idea that cellphone location information is so revealing, it should be better protected. Montana, Maine and other states have also passed laws backing the same approach. Those state efforts have given civil libertarians hope that they can get the federal courts to go along, something that might put chains on the NSA.
But George Washington University law professor Orin Kerr says, not so fast.
ORIN KERR: The state cases have no direct impact on federal standards because they're interpreting state constitutions, not the federal Constitution.
ABRAMSON: Federal courts have ruled consistently that the location of your cellphone is just like any other business record: already out of your possession and not protected by the Fourth Amendment. Kerr says until the U.S. Supreme Court says otherwise, information you give to a provider is fair game.
KERR: So far, courts have applied the third-party rule across the board. So as long as the information is disclosed to a third party, that's it.
ABRAMSON: Civil liberties groups point out that federal standards rest on Supreme Court rulings that date back decades, before mobile technology became so commonplace. They hope a cascade of favorable decisions in the states might push the federal courts to see digital information differently.
Larry Abramson, NPR News.