Names of the witnesses against him were withheld from the prisoner; but this had been found necessary under the circumstances. The Cathari assassinated many persons who denounced them, in the time of Gregory IX; and the Inquisitors decided that they could not count on the cooperation of the public unless they protected the denouncer by rigid secrecy. To offset this disadvantage for the accused, they permitted him to make a list of his enemies, and the testimony of any among them was rejected. A false denunciation, furthermore, was punished with the utmost rigor. The examinations were conducted with the greatest secrecy, to protect the reputations of the accused persons, in case they might be innocent.
William Thomas Walsh, Characters of the Inquisition (1940)