Defense lawyers appear angling for plea deal, in which defendant Dzhokhar Tsarnaev would admit guilt, avoid death penalty
Tamerlan Tsarnaev, main suspect in Boston Marathon bombing, met with an exiled Chechen activist in New Hampshire only weeks before attack
Information on Tamerlan Tsarnaev's activities leaked to Russian media indicates he was under extensive surveillance during stay in Caucasus region
Questions raised whether Moscow knows more about Tamerlan Tsarnaev's 2012 Dagestan trip than it's sharing with US
