Scrap that idea about Josh Harto being the riddler that was a bad suggestion. I've been writing a bit more and conjuring up ideas, and i came up with Harto's character Reece being killed in the third film.
With him publically going to the television and trying to reveal who batman was, people of gotham will presume he knows who batman is. Now the police need him for questioning about this as they think batman killed harvey dent.
When Reece is eventually found he is murdered with a riddle by his side and again the clues are for Gordon for the reasons i said before.