Lt. Travis St. Pierre, of the New Orleans Police Department, shows off a body-worn camera during a press conference in January. Brett Duke/The Times-Picayune/Landov hide caption

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Even if a suspect password-protects his or her phone, police still have some ways of getting into it. iStockphoto hide caption

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BlueJay, a tool by social media monitoring company BrightPlanet, shows the locations of tweeters who have left their geotagging option activated. BlueJay screenshot hide caption

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Protesters line up outside City Hall in Oakland, Calif., to demonstrate against the Domain Awareness Center, a data integration system being built by the city and the Port of Oakland. Martin Kaste/NPR hide caption

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