The 1999 Joint Director of Labs (JDL) revised model incorporates five levels for fusion methodologies including level 0 for preprocessing, level 1 for object refinement, level 2 for situation refinement, level 3 for threat refinement, and level 4 for process refinement. The model was developed to define the fusion process. However, the model is only for automatic processing of a machine and does not account for human processing. Typically, a fusion architecture supports a user and thus, we propose a Level 5 User refinement to delineate the human from the machine in the process refinement. Typical human in the loop models do not deal with a machine fusion process, but only present the information to the human on a display. We seek to address issues for designing a fusion system which supports a user: trust, workload, attention and situation awareness. In this paper, we overview the need for a Level 5, the issues concerning the human for realizable fusion architectures, and examples where the human is instrumental in the fusion process such as group tracking.