It's soooo obvious :D Nevertheless I was really really proud of myself when I figured it out!

Now let's have a look at RJ aliases or real names or whatever they are:

DR. Joe N. H. --> Anagramm of Red John --> Has got something to do with Red John which lead me to the idea that perhaps the names of the suspects could be a hint. Now look at what I found:

Roy Tagliaferro: Roy --> Comes from Kings and is once again a hint to RJ's arrogance

The interesting part however is Tagliaferro which comes out of the Italian and means something like "bend/cut iron"
Now let's take a look at SMITH! What does a Smith do? Exactly! He works with/ bends/ cuts iron!!

Obviously those are all aliases however it is so clear that Reede Smith is Red John --> Additionally to the whole Tagliaferro/Smith thingy there's also his surname which is Reede which comes from old English/Scottish and means *surprise-surprise* "red, or 'the reddish one'".

Sorry for the Spoilers but I just had to write somewhere that I'm the first Person I know of (in the Internet) to Figur this out :D