I have a different theory. I think Bertram is too obvious, plus if Bertram is Red John, I don't think he would have made the mistake of trying to kill Jane at the hospital. I don't think the sheriff or Reede Smith fit RJ's profile and as far as Brett Partridge faking his death because he is RJ, Jane has always said he is a "ghoul" but he seems too young, immature, and nervously jumpy around Jane. I think Partridge is/was a RJ groupie, but not Red John.

My theory is that Bob Kirkland's twin brother is Red John. This makes a lot of sense. His twin would fit RJ's profile, his voice seems right, and if he is a twin, he could have been confused with Bob Kirkland when he met Jane.