NOT ACTUALLY BOB KIRKLAND...HIS TWIN BROTHER MICHAEL!

I believe that Red John is Michael Kirkland.

He is only believed to be dead. He was a 'wild child', Bob tried to help him out, but didn't succeed. He was the victim of an abusive father which would tend to suggest he was not mentally stable and was exposed to violence at a very young age. 

I believe he joined visualize where he would have worked on the visualize farm, taking Acid etc this is where he started his killings.

In one of the more recent episodes, Bob Kirkland asked "do you recognize me" to Haibach..which I think is a clue from the writers.

Finally, it makes sense that Patrick wouldn't recognize Michael as another person he shook hands with, because he would have thought it was Bob Kirkland.