I believe it is either of the prime "dead" suspects, McAllister or Partridge. Jane naming Bertram as RJ serves two purposes: putting a crimp int to the activities of the Blake Association (as Bertram is the head or a high ranking member) and drawing out RJ, who will not be happy to have someone else take credit for his achievements. Having RJ be one of the dead suspects also allows Jane to kill them with impunity. Since Cho says McAllister is confirmed dead, and Partridge is dead, Jane cannot be charged with murder for killing a dead man.