§1. After the conclusion of the case, the judge can still summon the same or other witnesses or arrange for other proofs which were not requested earlier, only: 1/ in cases which concern the private good of the parties alone, if all the parties consent; 2/ in other cases, after the parties have been heard and provided that there is a grave reason and any danger of fraud or subornation is eliminated; 3/ in all cases whenever it is likely that the sentence will be unjust because of the reasons mentioned in can. 1645, §2, nn. 1-3 unless the new proof is allowed.
§2. The judge, moreover, can order or allow a document to be shown, which may have been unable to be shown earlier through no negligence of the interested person.
§3. New proofs are to be published according to can. 1598, §1.
Source: Code of Canon Law (Vatican.va)