Okay, It can't be Bertram. This is because he didn't recognize Kirkland when he allowed him to work on the red john case.. 
It can't be Reede Smith because he didn't even react to 'tiger tiger'. And he seems too young.

This leaves Mccallistar and Haffner...
Both are good whistlers Both are around 44, But we know McCallistar is afraid of pigeons as we saw in episode 3 at the end. I believed Haffner is Red John but it seems too obvious..Calling Lisbon by her first name etc. Next episode were going to find out why Haffner is not Red John just by looking at the promo.