The sonar is annoyingly unbelievable, as already mentioned.
But what really gets me is the ending. Batman taking the rap for those murders doesn't do any good. For a while, yes, the criminals might be extra cautious, fearing Batman now uses lethal force. But after a while, they'll realize that he won't, because Batman doesn't use lethal force. And the whole ruse will be for naught. Worse, the police will remain after Batman, and pissed at Batman, for a long, long time.