INTERVENTION IN A CAUSE. - It is the entry into the procedural relationship of a third party who was extraneous to it at the moment when it arose (can. 1852).
Intervention in a case is of various kinds. It is, in the first place, voluntary or compulsory (can. 1853), according as it is brought about by the spontaneous initiative of the third party or upon the request of one of the parties or by order of the judge. In turn, voluntary intervention in a case is distinguished into principal, accessory and litisconsortile, according as it is made ad excludendum iura utriusque competitoris or ad adiuvandum or on the simple presupposition of the fear that the judgment may cause prejudice to the intervener just as it would cause it to the party to whom the intervener, by effect of the litisconsortium, would find himself bound.
In particular, principal intervention in a case, as also accessory adhesive intervention, presupposes the following conditions: that there be a third party, that there be the pendency of the process in which the third party intends to intervene, that there be the interest of the third party in intervening and, finally, that there be, in the judge approached for the already pending judgment, the competence to take cognizance of the claim of the intervener. It is noted that, as regards the element of interest, it is enough that this be juridical, deriving, that is, from the incompatibility, by identity of petitum and of causa petendi, between the right that the third party asserts with the intervention in a case and that brought into the case by the parties. Since in this case the intervention in a case is voluntary, it is evident that the rights of the third party remain unprejudiced, should it not be carried out.
In accessory or simple adhesive intervention in a case, the third party has a legitimation that is not autonomous, but reflected. It is, that is, in function of the judgment already existing between the parties, or rather of the defense that one or some of these have put forward, so that the third party by a separate process would not be legitimated to proceed against the adverse party of that party in whose aid he proposes his intervention.
In autonomous adhesive or litisconsortile intervention in a case, finally, the third party intervenes to assert a right dependent on the petitum or on the causa petendi already brought into judgment, but, unlike principal intervention in a case, he puts forward not two distinct claims against the two parties to the process, but a single claim against one of those and, unlike adhesive intervention in a case, he has an autonomous legitimation that allows him to enforce his right even by a separate process.
In the two forms of compulsory intervention in a case (at the instance of a party or by order of the judge) the initial procedural conduct of the third party is characteristically passive. In compulsory intervention in a case at the instance of a party, as a rule, the interest of each of the parties to the case in the integration of the judgment with regard to the third party derives either from the fact that it considers the cause common to the third party, by identity or connection of objective elements, or from the fact that the third party has assumed the obligation to guarantee to the interested party the right brought into dispute. Compulsory intervention in a case by order of the judge, on the other hand, has no other condition than the discretionary evaluation of the process made by the judge, so that it may seem opportune to him, for economy of judgment and for the purpose of eliminating the danger of contradictory adjudications, once the pending cause has been held for any reason common to the third party, to order the citation of the latter. This form of compulsory intervention in a case usually occurs in causes of public interest and, having according to the majority of authors a merely instructional purpose, can be realized even at the appellate stage.
Bibliography6 works
Fernando Della Rocca