The investigator's report was notably ________ ; although she possessed a wealth of anecdotal evidence suggesting systemic corruption, she refused to finalize her conclusions until more empirical data could be gathered.

The fact that she refused to finalize her conclusions until more empirical data could be gathered suggests that she was careful and cautious. While a scrupulous person is cautious and careful, it is to avoid mistakes that he might commit or hesitate to do things imperfectly. It is about his internal moral compass. It also suggests thoroughness and attention to detail. But in this particular case, the conclusions are not yet finalized, so scrupulous cannot be applied. We also know that she was looking for more empirical data. So it is more a case of looking outward, and being prudent and rigorous than having an inner moral compass. Therefore, circumspect is the right choice.