I've been on the fence about Haffner, but when someone here theorized that he managed to 'hide' his tattoo (or it was more of a vertical one, more easily hidden), I went back and rewatched that scene in 6x06. Watched it on my ipad, so I was able to grab a screen shot of the one and only close up we get of that moment, and I have to say...seems plausible (esp if his tatt is in a vertical configuration). Have a look : https://sites.google.com/site/mentalistkt/