Though he isn't considered a suspect, a former Chechen separatist who is now a refugee in the United States has become a key target of information in the Boston Marathon bombing investigation.
Musa Khadzhimuratov—who knew Tamerlan Tsarnaev and his wife and hosted them at his home a few weeks before the bombing—has been questioned "dozens" of times by the F.B.I., according to The New York Times, and the feds have apparently searched his apartment, his computers, given him a lie detector test, and taken DNA evidence.
Khadzhimuratov is reportedly the current focus of an effort to establish if Tsarnaev had any contact with members of the radical Islamist community, either in Chechnya or the U.S. Although there doesn't appear to be any evidence to contradict the current theory that Tamerlan and his brother were "self-radicalized," Khadzhimuratov says he and his family have been subjected to heavy scrutiny—and he's worried that the Russians are to blame.
For the rest of the story: http://www.theatlanticwire.com/global/2013/05/former-chechen-rebel-boston-marathon-bombing/65329/