Philip Bump explains the significance of the reports that the government had Tamerlan on its terrorist watch-list:
The terror watch list, as it’s known, isn’t really a watch list. For one thing, it isn’t regularly watched. For another, it’s not one list. It’s more of a set of hierarchical, integrated databases which are checked under various circumstances, most notably when individuals want to travel. According to Reuters, after he was interviewed by the FBI in 2011, Tsarnaev was added to the Terrorist Identities Datamart Environment, or TIDE, which is compiled by the National Counterterrorism Center. It’s a list that comprises over half a million names. “Because of its huge size,” Reuters reports, “U.S. investigators do not routinely monitor everyone registered there, said U.S. officials familiar with the database.”
In other words, there’s a sort of pyramid of terror investigation. At the bottom of the pyramid are hundreds of thousands of people who’ve come to the government’s attention for some reason. As the FBI and other agencies look into behavior and patterns, people can move up the pyramid — fewer people evincing more suspicious behavior — winnowing to a point once held by Osama bin Laden. Or, after a determined time, people can drop out of the pyramid entirely if they don’t behave in a way that raises suspicion. That’s the track Tsarnaev was on.
Previous Dish on the information that the government had on the bombers here.
(Chart from John Hudson)
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