A. INTRODUCTION
The Code of Civil Procedure No. 6100 ("the Code") sets forth the fundamental procedural rules governing civil proceedings within the field of private law. One of these provisions is the institution of intervention, which allows third parties who are not parties to the pending case to participate in the proceedings.
By incorporating the mechanism of intervention, the Code aims to ensure that proceedings concerning a matter affecting a third party are conducted in a fair, consistent, and procedurally economical manner. The institution of intervention is regulated under two types in the Code: principal intervention and accessory intervention. In this article, these institutions, which enable third parties to take part in judicial proceedings, will be examined separately in terms of their legal nature, conditions, and effects on the proceedings.
B. PRINCIPAL INTERVENTION
Pursuant to Article 65 of the Code, principal intervention may be defined as a situation where a third party, in a pending contentious or non-contentious proceeding, files an independent action before the same court by asserting a right over the subject matter or property of the proceedings that conflicts with the interests of the parties to the pending case.
The parties to a principal intervention action consist of the principal intervener and the plaintiff and defendant of the original case. Due to this structure, the requirement to assert the disputed right against all parties and to render a single judgment against all of them is referred to in practice as compulsory joinder of parties.
In order to resort to principal intervention, certain conditions must be cumulatively met. These conditions may be listed as follows:
- The existence of a pending case,
- The intervener not being a party to that case,
- The intervener asserting, in whole or in part, a right over the disputed right or property,
- The request for intervention being submitted before a judgment is rendered in the original proceedings.
It is accepted as the prevailing view in both legal scholarship and the case law of the Court of Cassation that a request for principal intervention cannot be submitted during the appellate stages, namely before the regional courts of appeal or the Court of Cassation.
A principal intervention action is conducted and adjudicated together with the original proceedings. As a party to the proceedings, the principal intervener may carry out all procedural acts. Therefore, the intervener's procedural acts may directly affect the judgment to be rendered in the original case.
C. ACCESSORY INTERVENTION
Pursuant to Article 66 of the Code, accessory intervention refers to the participation of a third party in a pending case, alongside and in support of one of the parties, until the completion of the investigation stage, provided that the third party has a legal interest in the success of that party. In this way, the accessory intervener seeks to contribute to the success of the party they support and thereby prevent any potential future action that could be brought against them. By this feature, accessory intervention serves both procedural economy and the prevention of contradictory judgments.
An accessory intervener is not a party to the proceedings and, therefore, may only carry out procedural acts from the point at which they enter the proceedings, under the procedural control of the party they support. Accordingly, the accessory intervener may not perform any procedural acts that would be detrimental to the supported party or that would have the effect of a disposition over the case, such as waiver or settlement. Moreover, as the accessory intervener does not have party status, the concept of joinder of parties is not applicable.
In order to resort to accessory intervention, the following conditions must be cumulatively satisfied:
- The existence of a pending case,
- The intervention being made before the completion of the investigation stage,
- The intervener not being a party to the case,
- The intervener having a legal interest in the success of the supported party,
- The intervener having the capacity to be a party and to sue.
Another important point is that accessory intervention is not permissible at the appellate stages, namely before the regional courts of appeal or the Court of Cassation.
Accessory intervention may occur either upon the notification of the case to a third party by one of the parties who contemplates bringing a recourse action against that third party in the future, or without any such notification. However, timely notification produces legal consequences with respect to any potential future recourse action; a third party who, despite having been notified, does not join the case as an accessory intervener cannot avoid the consequences of the judgment.
As the accessory intervener does not have party status in the main proceedings, the judgment will produce legal effects only between the parties. However, since the judgment will have conclusive evidentiary effect in any subsequent recourse action, it will also have indirect consequences for the accessory intervener. For instance, the accessory intervener cannot later argue that the judgment rendered in the first case was incorrect; such judgment may both limit their right of recourse and affect the amount of recourse in any future action they bring or that may be brought against them.
D. COMPARISON OF PRINCIPAL AND ACCESSORY INTERVENTION
Principal Intervention: A third party joins a pending case by asserting an independent right over the disputed subject matter in their own name and thereby acquires the status of an independent party. Accordingly, they may independently carry out procedural acts during the proceedings, submit evidence, expand their claims and defenses, and exercise the power of disposition over the subject matter of the case. The request must be submitted before a judgment is rendered, and principal intervention is applicable in both contentious and non-contentious proceedings.
Accessory Intervention: A third party participates in the proceedings solely as a supporter of a party whose success they have a legal interest in, without acquiring party status. They have no authority to act independently; their procedural acts are subject to the approval of the party they support. They do not have the power of disposition over the subject matter of the case, and no judgment is rendered against them; however, the judgment rendered may have conclusive evidentiary effect in a potential future recourse action. The request must be submitted before the completion of the investigation stage, and accessory intervention is applicable only in contentious proceedings.
E. CONCLUSION
The institution of intervention in proceedings, as regulated under the Code, aims to protect the legal interests of third parties while ensuring the efficiency of judicial proceedings. Depending on the circumstances of the case, either principal intervention or accessory intervention may be pursued, and these two types differ from each other in terms of party status, procedural powers, and the effects of the judgment.
For these reasons, when evaluating requests for the participation of third parties in proceedings, the type of intervention and its legal consequences must be taken into consideration. Determining the appropriate type of intervention is of great importance both for the protection of third parties' rights and for the conduct of the proceedings in a fair and procedurally proper manner.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
