This paper starts from the observation that judicial investigations have long played a marginal role in Arabic literature. As a historian, and not a literature specialist, I question the institutional background of such marginalization. It appears that, although some judges practiced investigations in the early days of Islam, Muslim jurists abandoned this practice towards the end of the Umayyad period because of its potential arbitrariness. The qadi's justice system transferred the entire investigation process on the reliability of witnesses. Only secular judicial institutions (police, maẓālim) continued to seek the truth beyond appearances. However, the poor reputation of police officers also led to their literary marginalization.