The reasons for the prohibition of the revelation of the names of witnesses notwithstanding, Henry Charles Lea has excoriated the Inquisition in unmeasured language for this “crowning infamy”…This opinion in regard to the relative procedure in inquisitorial tribunals and secular criminal courts is so general among historians that it passes for unquestioned, accepted historical fact. Unfortunately such facile generalizations too often fade and disappear in the mist before the strong glare of the searchlight of historical examination…
From an examination of the principal primary sources of French law of the thirteenth and fourteenth centuries and the better modern legal historians the following pattern seems to emerge. In the thirteenth century, particularly under Louis IX, the procedure d’enquete was substituted for the judicial duel. The witnesses gave their testimony in private, but the depositions were made available to the accused. Actually, the witnesses took their oath in the presence of the accused, who could at that time challenge their integrity. Thus the development in written law seems to have been that, whereas in Roman Law the witnesses testified in the presence of both parties, in Canon Law in order to assure independence they were heard in secret while the depositions were put into writing and published…Administered in this fashion, nothing would seem more legitimate than this restriction, for, if one diminished for the witnesses the causes of intimidation, one did not hide the testimony on which the judge would form his decision.
However both the Church and the civil government discovered that this manner of acting did not give sufficient security to the witnesses. The Church, as we have already seen, in exceptional procedure – the Inquisition for heresy – sought to reassure the witnesses but did not touch, even in this special case, the publication of the testimony; she confined herself to prescribing simply the concealment of the names of the witnesses in the reading which was made to the accused of the depositions and in the copy which was given to him.
Albert Shannon, “The Secrecy of Witnesses in Inquisitorial Tribunals and in Contemporary Secular Criminal Trials”, Essays in Medieval Life and Thought: Presented in Honor of Austin Patterson Evans (1965