Looking back, I can tell that Ray Haffner was by far the most capable suspect of being Red John.From his very first moments on the show he appeared to observe Jane and how he works, he was friendly and helpful.Then it comes the interest for Lisbon which is more than obvious.Haffner sees Jane as a rival at this point.In addition Haffner is the only one of the 7 suspects who has links on both BA and Visualize.He is handsome, seductive and he seems to have a dark persona in the background.He was at the barn 25 years ago.Lisbon doesn't get killed by Red John, and the only possible explanation is that he has a crush on her.He fits the age, the body type and the personality. Also, for those who say that Rj is McAllister and he didn't kill Lisbon because of the pigeons, remember that at the barn, the smiley was painted on the outside.For what reason?Red John could have painted it inside.My guess?Haffner fears spiders, and in this room there could be a lot of them.So, he was afraid to finish his work and get out to do so.In addition, to answer on the previous theory over Haffner, we can assume by the way McAllister acts at the church that he was hypnotized to believe that he is RJ.

Still, there are a lot of things that puzzle me and kinda cancel this theory:
Haffner seems to be naive.Observe how easily Jane tricks him with the little book.And how easily Lisbon understands that he is a member of Visualize.Of course those could be done on purpose, but that is hard to tell.