In the book Code Of Honor?
The BEST explanation for why Kamran believes that his brother, Darius, is innocent is that he...
knows that his family has no religious preference, so there is no motive for Darius.
witnesses Darius reciting the military academy's oath.
insists that somebody from Homeland Security is controlling Darius.
has grown up with Darius, so he knows his brother better than anybody else.