I know Teresa is Red John. Why? I could give you all pointers in the serie that would make you 100% sure. But what is the fun in that. READ this and look for them yourself. And trust me after reading this you will look ;)

How come red john never knows when Jane is on to her until shes "Filled-in on his plan? And then we all know what happends after. Jane fails just in the last moment when she knows whats going to happen. And like the murderous pshyco as she is, with vain imprinted in her. She comes to Patric in the aftermath to be his concerned friend. But really shes there to se his pain of coming soo close but not Suceeding in the task. That gives her proof of his weakness of trust and his lack of seeing things clearly.. Thats What i would do :) And Hey!

TERESA LISBON mirror-it and make out TESA IS RED JON
(Teresa is often spelled with H between T and E that Would be TESA IS RED JOHN

Happy hunting people... I think i feel like her right now. Knowing everything and using you like puppets.