I have absolutely no idea who the body is. I agree with you it's almost certainly not Daniel for a number of reasons, but other than that I'm really not sure. Maybe Tyler, since they have set up his wanting to steal Daniel's identity, which could explain why Charlotte confuses them (if he's wearing Daniel's clothing and/or imitating his hairstyle). Though I think that would be a bit of a waste -- he knows so much, it seems like it would be better to keep him locked away on the sidelines for a while, and bring him back to cause more trouble in future seasons.

I agree that it is almost certainly Jack on trial, but he won't be the actually killer. I HOPE it is -- it would give him more to do and hopefully flesh out his character more; plus it would REALLY cause Emily to have to re-evaluate what exactly she's doing, and how much he's hurting others.

Not sure who the killer is. If the body IS Tyler, I could see the killer being Daniel, actually. But if it's not we're back to square one. Maybe Fauxmanda? That would explain why Jack helps...