The most recent scholarship (Kéry) has demonstrated that prelates had been ordered to investigate (inquisitio veritatis) since the pontificate of Pope Alexander III (1159-1181).   By the end of the pontificate of Innocent III the obligation and the duty of bishops to prosecute clerical crimes had become firmly established as an important part of ecclesiastical procedure.

Lotte Kéry, “Inquisitio - denunciatio - exceptio: Möglichkeiten der Verfahrenseinleitung im Dekretalen-recht,” Zeitschrift der Savigny-Stiftung für Rechtsgeschichte: Kanonistische Abteilung 87 (2001) 226-268.