This chapter asks whether international law imposes a positive duty on parties to a conflict to investigate civilian deaths. It first considers the general obligations on parties to conflict to account for the missing and the dead, particularly after any engagement to perform examinations, and to mark and register grave sites. Second, it turns to specific obligations on parties where a suspected violation of IHL has occurred. Third, it considers briefly additional investigatory obligations that apply in the case of a suspected war crime or other violation of international criminal law.