First of all:
Jane never shook hands with these guys: Stiles, McAllister, Partridge and Smith. Rewatch all the videos when Jane first meet these people, and you will see that they nevere shook hands. So they are out from this 7 suspects list. So: Bertram, Haffner and Kirkland.
Jane can manipulate Bertram, and he seems to care too much about he's career inside CBI to be Red John. He is just an acomplice to Kirkland or maybe Red John.
Haffner is good guy, he plays after the rules, and i think he cares too much about Visualize. I don't think that he is Red John, this will be too obviously.
Kirkland will be my guess, because he has the money, the power, the position and the knowledge to create fake names, fake companies and breake into CBI security sistem without being traced.
He already breake into Jane office, and he kill Jason Lennon (season 5, ep. 18) after Kirkland ask Lennon if he recognises him. This suggest that Kirkland already knew Lennon. If Kirkland wanted Red John, he wouldn't kill Lennon.
Also, Kirkland is watching Jane from his beginning in CBI. He has a odd voice, short straight hair and he fit Red John body. (season 2 ep. 23)
Heller said that we all are gonna be disappointing, when we find out who Red John is, and i am disappointed already.