§1. Judges and tribunal personnel are always bound to observe secrecy of office in a penal trial, as well as in a contentious trial if the revelation of some procedural act could bring disadvantage to the parties.
§2. They are also always bound to observe secrecy concerning the discussion among the judges in a collegiate tribunal before the sentence is passed and concerning the various votes and opinions expressed there, without prejudice to the prescript of can. 1609, §4.
§3. Whenever the nature of the case or the proofs is such that disclosure of the acts or proofs will endanger the reputation of others, provide opportunity for discord, or give rise to scandal or some other disadvantage, the judge can bind the witnesses, the experts, the parties, and their advocates or procurators by oath to observe secrecy.
Source: Code of Canon Law (Vatican.va)