I think it is one of two things.
1. He is going to get close to Naz and then say he confessed to the murder to him to help him get out of jail earlier.
or
2. And this is the theory I believe to be true. He knows Naz didn't do it because he knows who did do it and he feel sorry for Naz. I think he pretty much knows everything that goes on because of his contacts and he knows Naz didn't do it.