Section I. The Ordinary Contentious Trial - Title V. Incidental Cases
Can. 1587 An incidental case arises whenever, after the trial has begun through the citation, a question is proposed which nevertheless pertains to the case in such a way that it frequently must be resolved before the principal question, even if it was not expressly contained in the libellus which introduced the litigation.
Can. 1588 An incidental case is proposed in writing or orally before the judge competent to decide the principal case, indicating the connection between this and the principal case.
Can. 1589 §1. After having received the petition and heard the parties, the judge is to decide as promptly as possible (expeditissime) whether the proposed incidental question seems to have a foundation and a connection with the principal trial or rather must be rejected at the outset. If the judge admits the incidental question, the judge is to decide whether it is of such gravity that it must be resolved by an interlocutory sentence or by a decree.
§2. If the judge decides not to resolve the incidental question before the definitive sentence, however, the judge is to decree that the question will be considered when the principal case is decided.
Can. 1590 §1. If the incidental question must be resolved by sentence, the norms for the oral contentious process are to be observed unless the judge decides otherwise due to the gravity of the matter.
§2. If the matter must be resolved by decree, however, the tribunal can entrust the matter to an auditor or the presiding judge.
Can. 1591 Before the principal case is completed, the judge or the tribunal can revoke or reform the decree or interlocutory sentence for a just reason either at the request of a party or ex officio after the parties have been heard.
Chapter I. Parties Who Do Not Appear
Can. 1592 §1. If the cited respondent has neither appeared nor given a suitable excuse for being absent or has not responded according to the norm of can. 1507, §1, the judge, having observed what is required, is to declare the respondent absent from the trial and decree that the case is to proceed to the definitive sentence and its execution.
§2. Before issuing the decree mentioned in §1, the judge must be certain that a legitimately executed citation has reached the respondent within the useful time, even by issuing a new citation if necessary.
Can. 1593 §1. If the respondent appears at the trial later or responds before a decision in the case, the respondent can offer conclusions and proofs, without prejudice to the prescript of can. 1600; the judge, however, is to take care that the trial is not prolonged intentionally through longer and unnecessary delays.
§2. Even if the respondent did not appear or respond before a decision in the case, the respondent can use challenges against the sentence; if the respondent proves that there was a legitimate impediment for being detained and there was no personal fault in its not being made known beforehand, the respondent can use a complaint of nullity.
Can. 1594 If the petitioner has not appeared on the day and at the hour prescribed for the joinder of the issue and has not offered a suitable excuse:
1° the judge is to cite the petitioner again;
2° if the petitioner does not comply with the new citation, the petitioner is presumed to have renounced the trial according to the norm of cann. 1524–1525;
3° if the petitioner later wishes to intervene in the process, can. 1593 is to be observed.
Can. 1595 §1. A petitioner or respondent who is absent from the trial and has not given proof of a just impediment is obliged both to pay the expenses of the litigation which have accrued because of the absence and to indemnify the other party if necessary.
§2. If both the petitioner and the respondent were absent from the trial, they are obliged in solidum to pay the expenses of the litigation.
Chapter II. The Intervention of a Third Person in a Case
Can. 1596 §1. A person who has an interest can be admitted to intervene in a case at any instance of the litigation, either as a party defending a right or in an accessory manner to help a litigant.
§2. To be admitted, the person must present a libellus to the judge before the conclusion of the case; in the libellus the person briefly is to demonstrate his or her right to intervene.
§3. A person who intervenes in a case must be admitted at that stage which the case has reached, with a brief and peremptory period of time assigned to the person to present proofs if the case has reached the probatory period.
Can. 1597 After having heard the parties, the judge must summon to the trial a third person whose intervention seems necessary.