When the 5 suspects are lifting up their shirts, Bret Stiles has SOMETHING on his left shoulder that looks quite a bit like the Red John smiley face.  Take a look at the scene again.  If you use this link...

http://www.cbs.com/shows/the_mentalist/video/rHeKqQGu9y_H4sH8GWz0grvjqJOLbpFb/the-mentalist-fire-and...

...stop at 40:14 and you will see.