Yeah, I also thought when he hit Peach with that rock: Gosh what are you're doing? You hold it with bare hands and throw away like 20 meters from the scene of the crime?
Anyway, I think, for cameras etc. you need to know what are you're looking for, same with the DNA, and on the other hand the guy is literally crazy, so he probably he doesn't care. And it's a TV world, most of the rules of the "real" life just doesn't really exist.