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This is ALL THINGS CONSIDERED from NPR News. I'm Audie Cornish.
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And I'm Robert Siegel. As part of our coverage of the Boston bombings, we begin this hour with two stories. We'll hear about the design of the bombs and what they might reveal about the plot. But first, questions of surveillance and privacy. Footage from cameras along the Boston Marathon route gave the FBI important clues, and prosecutors say they will use some of those images to try to prove their criminal case against Dzhokhar Tsarnaev.
Still, as NPR's Carrie Johnson reports, the proliferation of cameras in America's big cities is raising some tricky questions.
CARRIE JOHNSON, BYLINE: It was pictures of two brothers taken by a camera outside the Lord and Taylor department store that provided the first break in the Boston Marathon case. Former Homeland Security official Stewart Baker...
STEWART BAKER: What was perfectly obvious after the attack was the most important thing was to know who had attacked us and to begin the process of tracking them down. And the cameras were absolutely essential for that purpose.
JOHNSON: Baker says even though some amateur sleuths at first misidentified the men in those images, he expects to see more cameras playing a big role in investigations - not to deter crime but to catch criminals after the fact. Similar images helped authorities in London get to the bottom of who bombed the underground subway system there back in 2005, with one important difference, says Julian Sanchez, a research fellow at the Cato Institute.
JULIAN SANCHEZ: On the one hand, you have a centralized network surveillance cameras of the kind that are familiar from London's famous Ring of Steel and in the United States in Chicago.
JOHNSON: Those closed circuit TV cameras throughout London are operated by the government. Boston has only about 60 cameras controlled by law enforcement, Sanchez says. The cameras that proved so helpful there last week were privately owned.
SANCHEZ: In a way, private, distributed surveillance cameras create a kind of network of little brothers instead of a Big Brother. So you get the same benefits, to a great extent, without incurring the risks to civil liberties.
JOHNSON: Those cameras owned by local businesses target small areas. They capture activity that most people in that public place can see with their own eyes. And they usually record over themselves every week, cutting down on the intrusions to privacy. One more thing: Those company-owned cameras generally don't feedback to a big networked system where police are watching.
Ben Wizner works at the American Civil Liberties Union. He says he has no objection to the way law enforcement used surveillance in Boston.
BEN WIZNER: I think in some ways this is an easy case because when there's a crime of this nature, there's no problem whatsoever for the police to get any kind of permission they need from judges in order to conduct surveillance.
JOHNSON: Wizner says that means going to a judge to get a warrant for the images on privately-owned cameras or taking advantage of an emergency exception in the law to get that footage more quickly. But, he says, surveillance can go too far.
WIZNER: The questions that we have are: Do we want a society in which cameras are literally everywhere and we can't walk down the street holding someone's hand without being recorded in a government database? And then, what happens to all of this personal footage - almost all of which does not capture terrorists - when the event has been solved?
JOHNSON: The ACLU says it wants authorities to be careful about storing those images of innocent people in law enforcement databases with no time limit for erasing them. Congressman Adam Schiff, a Democrat from California, says the tug of war over privacy is nothing new.
REPRESENTATIVE ADAM SCHIFF: It goes back to the Constitution. It was part and parcel of the Fourth Amendment right to be free of unreasonable searches and seizures. We've always expressed a strong constitutional preference for privacy, for not giving the government unbridled authority, even to protect us.
JOHNSON: Schiff, a member of the House Intelligence Committee, says that means we sometimes take risks, but he says that's all part of living in a free society. Carrie Johnson, NPR News, Washington.
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