Bob Kirkland is Red Jonh....
wh0 :
1. He say 'Thank You' to FBI's boss , when she called the former CBI boss, Virgil. (season 5 episode 5)
2. Homeland Security (season 5 episode 7)

Why :
1. Lorelei Martins had spoken accidently to Jane that Red John 'had shake his hand' with Patrick Jane.
And Bob Kirkland (Red John, assumed) had 'Shake his hand' with Jane, and Jane didn't know him (Season 5 episode 7)
2. Bob's sound is very similar with Red John's
3. Bob lead investigation searching lorelei Martins whe she break the federal prison with Jane (season 5 episode8) and after that, Bob is just dissapear.