§1. After the proofs have been collected, the judge by a decree must permit the parties and their advocates, under penalty of nullity, to inspect at the tribunal chancery the acts not yet known to them; furthermore, a copy of the acts can also be given to advocates who request one. In cases pertaining to the public good to avoid a most grave danger the judge can decree that a specific act must be shown to no one; the judge is to take care, however, that the right of defense always remains intact.
§2. To complete the proofs, the parties can propose additional proofs to the judge. When these proofs have been collected, it is again an occasion for the decree mentioned in §1 if the judge thinks it necessary.
Source: Code of Canon Law (Vatican.va)