A year after the Boston Marathon bombings, prosecutors say they have a trove of evidence to use against suspect Dzhokhar Tsarnaev.
Prosecutors say they have surveillance video showing Dzhokhar placing one of the bombs just yards from an 8-year-old boy who died in the blast. They also say Dzhokhar wrote a defiant confession inside a boat he was found hiding in several days after the bombings.
Tamerlan Tsarnaev, Dzhokhar’s brother, was killed in a shootout with police. Dzhokhar has pleaded not guilty and is facing a November trial.
But there are still many unanswered questions, such as how much did he do to help plan and carry out the attacks? Was his brother Tamerlan the "main instigator," as Dzhokhar's lawyers say? And did federal authorities underreact to a warning from Russia that Tamerlan was becoming radicalized?
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