Embodiments of the inventive concept reduce the burden of creating litigant sources of evidence or other evidentiary materials in connection with litigation in a court of law. Designation of at least one document file included in digital document information is accepted and designation of a language into which the designated document file is translated is accepted. The document file, the designation of which is accepted, is translated into the language the designation of which is accepted. A common document file representing the same content as that of the designated document file is extracted from digital document information recorded in a recording unit. Translation-related information representing that the extracted common document file is translated by invoking a translated content of the translated document file is generated, and, based on the translation-related information, a litigant-related document file is output.