Boston Marathon bombing 'instigated by brother'

Lawyers for Boston Marathon bombing suspect Dzhokhar Tsarnaev have asked a judge to make prosecutors turn over family-related evidence as they try to build a case that his older brother was the “main instigator” of the deadly attack.

The defence team is seeking a host of records from prosecutors, including any evidence to support its claim the FBI had asked Tamerlan Tsarnaev to be an informant.