You ahve already given the answer...simple...cos the CBI wants to make a scapegoat out of a poor man.....and wants to spare the powerful and connected people!! Even if Krishna is the murderer, he is definitely not the mastermind or the brain behind it...we all know that...it doesn't need much intelligence to figure out that the root behind this murder is some underhand shady stuff carried out by doctors in which Aarushi has been made an innocent victim!!
