We may have been misdirected in the Red Barn episode. Father DiBuono told Jane that Talbot said some "kid" painted the Red John smiley and from that statement we've be led to believe that was the same person who actually murdered Talbot and Charney. But what if Talbot and Charney were killed by Stiles (cleaning up a mess, which it seems the Red Barn was) and noticed the smiley, which appears to be derived from a Visualize ritual (like we see in "Fire and Brimstone"), and decided to adopt it. So the Red Barn wasn't necessarily the birth of Red John as much as the birth of the smiley.

Net is, we were led to believe that the "kid" who painted the smiley commited the murders, but there is no proof that is the case. This could simply be the writers providing some interesting background (origin of the smiley) and conveniently using that as a way to misdirect us and remove suspicion from Stile.