I wonder why the defense concedes the messages are his.
If he sent pictures of his anatomy, I'm sure those might be identifying as well. I don't know that you'd want the pictures put into evidence by questioning whether the sexting was Ross Harris' or not, or to otherwise make a big deal about the sexting. Why draw more attention to something so dumb?
Could you imagine what the testimony would be like if they questioned whose organs were in the pictures Ross Harris sent? I remember a scene from Porky's...