A couple of things to add into you considersation:
1. Miles (the Bama basketball player who owned the gun) texted Miller and told him to bring the gun. Now, you and I can recall fact patterns from law school (particularly Evidence) when silence can be inferred to mean something when someone would have/should have otherwise been under a duty to speak, so I tend to think that the claim of "absolute ignorance" is at least questionable and debatable when you get a text to "bring the gun and leave the cannoli".
2. Miller is trying to make the claim that he was only at the murder site to "pick up" Miles. However, instead of Miles getting in the front seat and leaving with Miller, he rummaged around in the back seat until he found the gun. Again, that may not be ABSOLUTE proof that Miller knew what was about to happen, but it at least need to be explored, and I have no idea why the Tuscaloosa police and prosecutors are approaching the investigation so weakly.
3. And don't even get me started on the most recent Alabama game, with the "patdown" humor. Further proof that Miller simply does not comprehend the seriousness of his involvement IN A MURDER.