New suspect!! Marshall, Summer´s new fiance.

remember 1 clue was: "he was mar.." marshall fits this and all the other clues given by rosalind.
his face seems familiar cause i´m pretty sure it has already appeared in other episode and maybe he shake hands with patrick!! (so if you have previous episodes: go look for him!! -couse i don´t have them :( - if you find him: you have found RedJhon!! :D

By the way, and according to what lorelei told jane:
1. patrick himself cannot be red jhon (because he and RJ have shaken hands,and this can´t be done with oneself)
2. RJ can´t be any other of his CBI friends (namely: vanpelt, risgby, cho, lisbon)