Jurors who may have been studying the defendant in recent days at the federal terrorism trial here of a 21-year-old Somali-American named Mohamed Osman Mohamud have seen a thin, neatly dressed young man at the defense table who sometimes quietly confers with his lawyers.
But on Tuesday they got a drastically different view as video and audiotapes secretly recorded by the F.B.I. in 2010 revealed a sometimes bombastic, sometimes swaggering religious militant who said repeatedly he was willing to kill and die as a martyr if need be.
