This patent describes a method and apparatus to automatically and accurately winnow down arbitrarily large amounts of electronic information created by a particular population of actors to only those subsets of particular interest by having a causal relationship, even when retrieved documents containing this information do not individually satisfy the search criteria used. An actor in this context is defined as any entity, single or aggregate, capable of creating, distributing, modifying, or receiving digital information. Once identified, this subset of information may, for example, be processed, analyzed, redacted, or destroyed, depending on the context of the system's use.