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The Supreme Court on Tuesday will take up a hot-button issue of privacy in the digital age: Can police, without a warrant, rummage through the cell phones of people they arrest?

It's an important case, given that more than 90 percent of American adults now own a cell phone and 58 percent have a smart phone.

And more than 12 million people are arrested in the U.S. each year, most of them for minor offenses, such as drunk driving or getting in fights.

Police also have authority to make arrests for fine-only infractions like driving without a seat belt, littering, or jaywalking.

So, allowing police to search the text, photo, and video files on all of those smart phones would severely compromise personal privacy, says Jeffrey Fisher of Stanford Law School.

"Such files hold exponentially greater amounts and types of sensitive personal information than any physical item" an arrested person could carry.

While the Constitution ordinarily requires police to get a search warrant before looking at someone's personal possessions, the courts have granted an exception when a person is taken into custody.

The U.S. Justice Department and the State of California argue that's justification enough for looking at the contents of a smart phone.

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"Computer search and seizure is the new frontier. These are the first cases of many that the Supreme Court will decide in the area, so they'll be very important for the future of the law."

The Supreme Court will now hear two cases on the privacy issue, both involving criminal defendants who sought to have evidence taken from their phones thrown out on the grounds that the police did not first get a warrant. Lower courts came to opposite conclusions in their cases.

In one, Fisher represents David Leon Riley, who was pulled over in San Diego five years ago for driving with an expired license. When police found guns in his car, they arrested him for carrying concealed weapons.

Police then discovered pictures and videos on his Samsung smart phone which led to charges that he took part in violent gang-related crimes. His conviction was upheld.

In the second case, Massachusetts man Brima Wurie was arrested for dealing drugs. After taking him into custody, police learned where he lived by looking at a log of calls on his cell phone. At his home, they found more drugs and a gun. His conviction was overturned when the evidence from the phone was thrown out.

Lawyers for the two men argue that the courts have allowed police to search the possessions of people they arrest for two reasons — assuring officer safety and preventing the destruction of evidence. Neither interest, they say, is at stake with cell phones.

"The digital contents of a smart phone are categorically incapable of threatening officer safety. And once police have seized and secured a smart phone, there is no risk that the arrestee might destroy or alter its digital contents," Fisher argued in his court brief.

His position is supported by several privacy advocates, including the Electronic Frontier Foundation (EFF), who say that today's smart phones contain vast amounts of data that never before could have been carried around.

"The breadth of that information would likely reveal an individual's medical history, religious beliefs, political affiliations, network of friends, colleagues, intimate associates, and acquaintances," read a friend-of-the-court brief filed by EFF and others.

A modern smart phone, they argue, is essentially a compact computer that happens to include a telephone and stores the kind of highly personal information that in the past could only be found by searching a home desk, bank vault, and medicine cabinet.

But the same versatility that has made phones popular among ordinary citizens has also made them a tool of criminals, the Obama administration argues.

"It is now common for drug deals to be arranged by cell phones, for violent street gangs to communicate through text messages, and for child abuse to be recorded on camera phones," the Justice Department stated in its court filings. "In today's world, cell phones are particularly likely to contain evidence of unlawful activity and to help law-enforcement officers identify suspects they have apprehended."

The federal government and the State of California also argue that previous court decisions have upheld searches of items a suspect carries that may contain highly personal information, such as diaries, address books, wallets, briefcases, and purses. The Supreme Court is asked to decide whether cell phones merely contain more of what the police can already see without a search warrant, or whether the huge amount of data the devices hold puts them in an entirely different category.

Prof. Orin Kerr of the George Washington University College of Law, an expert in the field of police searches, noted, "computer search and seizure is the new frontier. These are the first cases of many that the Supreme Court will decide in the area, so they'll be very important for the future of the law."

The court is expected to decide the cases by late June.