Res judicata: Rules, requisites

Res judicata lays down two (2) main rules:
  1. The judgment or decree of a court of competent jurisdiction on the merits concludes the litigation between the parties and their privies and constitutes a bar to a new action or suit involving the same cause of action either before the same or any other tribunal; and
  2. Any right, fact, or matter in issue directly adjudicated or necessarily involved in the determination of an action before a competent court in which a judgment or decree is rendered on the merits is conclusively settled by the judgment therein and cannot again be litigated between the parties and their privies whether or not the claims or demands, purposes, or subject matters of the two suits are the same.[1]
There is res judicata where the following four essential conditions concur, viz.: 

(1) there must be a final judgment or order
(2) the court rendering it must have jurisdiction over the subject matter and the parties; 
(3) it must be a judgment or order on the merits; and 
(4) there must be, between the two cases, identity of parties, subject matter and causes of action.[2]

[1] Spouses Noceda, et al. v. Arbizo-Directo, 639 Phil. 483, 491 (2010).
[2] Genova v. De Castro, 454 Phil. 662, 675 (2003), citing Gallardo-Corro v. Gallardo, 403 Phil. 498, 507 (2001); Republic v. CA, 381 Phil. 558 (2000); Ayala Land, Inc. v. Valisno, 381 Phil. 518, 528 (2000); Bachrach Corporation v. CA, 357 Phil. 483 (1998); Alejandrino v. CA, 356 Phil. 851, 868 (1998).