Latest comment of mr Bruno Heller about a "very big clue" in last sequence of episode "The Desert Rose" had only strenghten the idea that Red John is the devil himself (pentagrams, 666's, marks of the beast etc. on walls when Lisbon enters the abandoned house and many other signs in previous episodes). He uses his minions to fulfill his deeds. Brett Partridge is nothing but another tool in this episode, like every person on the list that Patrick had made. The list of suspects is a second great plan (another one after his "year of despair") to roundup the real killer. Jane knows that he can't keep a secret unnoticed and just let it spread, Red John might take action and might make a mistake.

In my humble opinion the character known as Walter Mashburn is a human personification of devil, Red John, the only bed lover of Theresa Lisbon.