[blue-duncan]

The oath that the accuser takes is the “secret of the Holy Office”. What is that and does a breach of the oath carry with it excommunication as a penalty?

[lastchance]

If you look at the procedure as being more along the lines of a Grand Jury investigation than a trial you will understand it better and find it much less nefarious.

[Petrosius]

According to no. 11 of the INSTRUCTION the secret of the Holy Office is the strictest confidentiality "in all things and with all persons, under pain of incurring automatic excommunication, ipso facto and undeclared, reserved to the sole person of the Supreme Pontiff, excluding even the Sacred Penitentiary." But again I must stress the no. 13 expressly states that accusers, complainants and witnesses are not subject to censure, i.e. excommunication.

In any case, all this concerns only the knowledge of the investigation, not of the crime. Those involved with a criminal grand jury are under the same requirement for secrecy. Thus, there too, a witness could not reveal what he said to the grand jury but this does not stop him from making a public complaint about what the crime he witness. The secrecy only applies to his testimony.