Everybody says it cant be Bob Kirkland simply because he  was introduced in Season 5 episode 5. However that episode is a throwback episode showing how Jane met Lisbon and eventually was hired as a consultant to the CBI.  When we see Bob Kirkland for the first time its in the back of the limo after Virgil Minelli talks to Alexis Shultz. We then learn that Bob Kirkland has been there since the beginning. We just didnt know that till season 5. 

Now I will ask you this: What was the point of Alexis telling Minelli that Patrick was in an insane asylum? Maybe it was to get Milelli to think think Patrick shouldnt be trusted? Also in the season 4 finale when Patrick when he and "Redjohn" are talking Redjohn mentions the fact that he has a friend in the FBI. Alexis Shultz is in the FBI....coincidence?
 One last thing I must mention. Remember how Bruno Heller mentions the "Where is Waldo?" Game? What does Waldo always wear? Red and white. What does Kirkland always wear? A white shirt and some type of red tie. I dont know for sure if Kirkland is "RedJohn" but it is very good possiblity...