Alright, i think i know who red john is.
It's Brett Partridge.
First what we know about red john:
- He is just under 6 foot tall
-Oddly voice
-Very likely a man
-not too strong

Brett Partridge has an oddly voice, is just under six foot tall. Further he is the only one from the other characters who has a full name (unlike CBI Ron for example). He also is very macabre. Red John tells jane a poem by william blake: tyger tyger...
William Blake also made a painting called "a brace of partridges". you know what i mean.