Honestly folks, it might well be PJ himself or TL. But some time ago a thought crossed my mind that maybe Patrick's wife is somehow not that dead... and involved in the whole thing. It would be a very typical Hollywood-ending if PJ's wife was still alive and they'd either reunite at the end of the series (when Red John is killed) or we find out that she is Red John or one of his (therefore maybe PJ's) disciples...