Res judicata (Claim Preclusion)

1. Definition, Concept, and Legal Nature

Res judicata is the procedural phenomenon that confers the authority of law upon a judicial decision, rendering it immutable and preventing the same dispute from being re-litigated in future proceedings. According to the classical doctrine of Enrico Tullio Liebman, adopted by the Brazilian legal system, res judicata is not an effect of the judgment, but rather a quality that attaches to its effects, granting them permanence.

Regarding its legal nature, it is an institute of public order with the status of a fundamental guarantee. It is divided into:

• Formal Res Judicata: Refers to the immutability of the decision within the proceedings in which it was rendered, resulting from the preclusion of appellate remedies. It operates with purely intra-procedural effects.
• Material Res Judicata: Is the authority of the decision that projects its effects outside the proceedings (extra-procedural), preventing the sentencing command from being altered by subsequent laws or new judicial decisions (Art. 502, CPC/2015).

2. Historical Origin and Evolution in Law

Historically, the institute dates back to Roman Law under the maxim res judicata pro veritate habetur (the adjudicated matter is accepted as truth). In the classical period, the litiscontestatio already sought to avoid the renewal of litigation. With the Napoleonic codification and the rise of the Rule of Law, res judicata was consolidated as a pillar of the separation of powers, preventing Legislative interference in Judiciary decisions.

In Brazil, the evolution followed the Luso-Brazilian tradition, being elevated to constitutional status in the 1934 Charter and reaffirmed in all subsequent ones, culminating in the 1988 Constitution, which protects it as an entrenched clause (Art. 5, XXXVI).

3. Legal Provision and Normative Structure

The normative framework of res judicata in Brazil is robust and multifaceted:

• Federal Constitution (1988): Art. 5, item XXXVI – "the law shall not prejudice acquired rights, perfect legal acts, and res judicata".
• Code of Civil Procedure (2015): Arts. 502 to 508. Art. 502 defines it as "the efficacy that renders the decision on the merits, no longer subject to appeal, immutable and indisputable." Art. 503 delimits that res judicata applies to the operative part of the judgment.
• Law of Introduction to the Norms of Brazilian Law (LINDB): Art. 6, § 3 – Defines res judicata for the purposes of applying law over time.
• Code of Criminal Procedure: Arts. 110 and 621. In the criminal sphere, res judicata is mitigated in favor of freedom (favor libertatis), allowing for criminal revision at any time for the benefit of the defendant.

4. Practical Application and Contemporary Jurisprudence

The jurisprudence of higher courts has delimited the scope of res judicata, especially in the face of changes in constitutional understanding. The Supreme Federal Court (STF), in a recent general repercussion judgment, consolidated critical understandings:

STF Themes 881 and 885 (Cessation of Effects)

The Plenary of the STF decided that decisions that have become res judicata in tax legal relationships of successive performance automatically lose their effects if the STF subsequently decides to the contrary in concentrated control or general repercussion proceedings. In other words, tax res judicata is not absolute in the face of a new constitutional interpretation by the Supreme Court.

Relevant Súmulas (Precedents)

• Súmula 401 of the STJ: "The limitation period for a rescissory action only begins when no further appeal is possible against the last judicial pronouncement rendered in the proceedings."
• Súmula 259 of the TST: Deals with the immutability of the conciliation agreement, which has the force of material res judicata.

5. Correlated Principles and Doctrinal Divergences

The institute dialogues directly with the principles of Legal Certainty, Jurisdictional Effectiveness, and Due Process of Law. However, the debate on the Relativization of Res Judicata has emerged in doctrine.

The relativization school maintains that manifestly unjust decisions or those based on false evidence (such as a negative DNA test in a paternity investigation action prior to modern technology) should not be protected by immutability. The STF has already accepted this thesis in paternity cases (RE 363.889), prioritizing human dignity over procedural stability.

6. Contemporary Relevance and Practical Impacts

In the current scenario, res judicata faces the challenge of the "unitarization" of Law through binding precedents. The precedent system of the CPC/2015 seeks to avoid conflicting decisions that would generate insecurity, but the collision between an individual res judicata and a subsequent collective precedent remains one of the points of greatest tension in contemporary Procedural Law.

The practical impact is the need for strategic advocacy, attentive to the hypotheses of Rescissory Action (Art. 966, CPC) and Querela Nullitatis (absolute nullities of service of process), which are the legitimate instruments for undoing the authority of res judicata in exceptional and exhaustive cases.