1. A forensic system that acquires digital information recorded in a plurality of computers or servers and analyzes connection of the acquired digital information to a lawsuit, comprising: a result information receiving unit that receives result information which is a determination result of connection between the lawsuit and a document group including a predetermined number of documents, which is extracted from document data included in the digital information, by a user; an element selection unit that calculates evaluation values of elements which commonly appear in the document group in each result information item from the characteristics of the elements and selects the elements on the basis of the evaluation values; a score calculation unit that calculates a score of each document in the document data from the selected elements included in each document of the document data and the evaluation values of the selected elements; and a recall ratio calculation unit that calculates a recall ratio related to the determination of the connection to the lawsuit on the basis of the score.