In the short stories, we get several accounts of the death of samurai Kanazawa no Takehiro. The three people who could have witnessed his death, i.e. his wife Masago, the robber Tajōmaru and the samurai himself, give contradictory accounts of the events. Kanazawa no Takehiro's version is presented as that of a dead man's spirit as told through a medium.
What is not clear to me is whether Akutagawa or contemporary culture (early 20th century) assumed that a dead man's spirit wouldn't lie. If yes, the samurai's version would seem to be authoritative, unless the medium is unreliable. If no, it seems that the truth cannot be found.