In August 2007, Mr. Silber and Arvin Bhatt, then also an NYPD analyst, wrote what was then considered a controversial police-department report arguing that with the attrition of al Qaeda's leadership, the primary threat to New York would come from "homegrown" Muslims under the age of 35 who had become Islamists in the West.
Based on an analysis of 11 plots against Western targets between 9/11 and 2006, their report, "Radicalization in the West: The Homegrown Threat," concluded that most of the plotters were "unremarkable" citizens who had undergone often rapid radicalization, 90% of them in the West. The analysts identified a pattern of radicalization and listed common characteristics before a person committed a terrorist act. The report also warned: "The Internet is a driver and enabler for . . . radicalization."
Since 2007, the NYPD has looked for such warning signs among New York's Muslim population of 600,000 to 750,000—about 40% of whom are foreign-born—as homegrown terrorist plots have increased. In 2005, there was one homegrown terrorist plot in the U.S.; by 2010, there had been 12.
Tim Connors served as an Army officer in Afghanistan and now works for CAAS LLC, a New York-based consulting company that, among other things, trains police officers. He says that Tamerlan Tsarnaev fit the NYPD's radicalization profile perfectly. "His behavioral changes alone—never mind his overseas trip and Russia's warning to the FBI that he was a radical—would have been more than enough to trigger NYPD scrutiny," Mr. Connors says.
For instance, Tamerlan experienced a "family crisis" when his father left his mother in 2010 and then returned home to Dagestan. The 2007 NYPD report warned that such incidents often trigger radicalization. He also began exhibiting what the report calls "self-identification," when a person begins exploring radical ideas and dramatically changing his behavior—for instance, "giving up cigarettes, drinking, gambling and urban hip-hop gangster clothes" in favor of "traditional Islamic clothing" and "growing a beard."
Another red flag would have been Tamerlan's ejection from his local mosque, the Islamic Society of Boston, as reported by the Los Angeles Times. The paper disclosed last week that the elder brother was thrown out of the mosque after a shouting match with the imam during a Friday prayer service. The paper quoted several worshipers as saying that Tamerlan had yelled at the imam for having cited Martin Luther King Jr. as a role model for Muslims. Tamerlan protested, the paper said, because King was "not a Muslim."
The NYPD report cites "withdrawal from the mosque" as an indication of the onset of the "indoctrination" phase of radicalization. That is when a believer rejects traditional Islamic mentors in favor of "Salafist," or more radical, fundamentalist preachers and friends.
In New York, Tamerlan Tsarnaev's mosque quarrel and his sudden behavioral changes might well have been reported by concerned worshipers, the imam himself, or other fellow Muslims. The NYPD maintains close ties to Muslim preachers and community leaders, as well as a network of tipsters and undercover operatives.
