Impossible to be red john:
Cho
Rigsby
Van Pelt
Lisbon
Jane
Virgil Minelli
Possible but very unlikely:
Alexa Shultz
Gabe Mancini
Juniper Tolliver
Judge Manchester
Brett Stiles
Jason Cooper
Ellis Mars
Gale Bertrand
Agent Darcy
Royston Daniels
Rosalind Harker
JJ LaRoche
Hightower
Vint Molinari
Brenda Shettrick
Jane's dad
Tommy Lisbon
Amos Van Pelt
50/50:
Kristina Frye
CBI Ron
Brett Partridge
Walter Mashburn
Strong Suspects:
Bob Kirkland
Ray Haffner
Oscar Ardilles
Someone from Jane's past carnival life (e.g. twin brother)
According to the description given by rosalind harker,(just under 6 ft, average build, short straight hair) we can probably rule out walter mashburn, kristina frye (atho I do think she is BSing). Also, I think Brett Patridge and CBI Ron do not have the personality/attitude to be red john. We mgiht also rule out Oscar Ardilles for being too short but I am not sure about his exact height.
Hence my top suspects are Ray Haffer, Bob Kirkland (altho he might be too obvious) or someone from jane's past life like a twin brother (season 5 finale will feature people from jane's past so I think the writers of the show may be trying to create a connection here)
Thoughts?