Res Judicata is a principle or maxim in law that deals with cases already adjudicated and said cases, either quotes or the case itself is then used for substantiating the accuser or defendants proof of claim; expression of pre-existing rights, constitutional enforcement, the adherence to due process, or commanding the courts to act on a matter, make a decision or issue a judgment or decree in your favor, et alia.
Res judicata (RJ) or res iudicata, also known as claim preclusion, is the Latin term for "a matter [already] judged", and refers to either of two concepts: in both civil law and common law legal systems, a case in which there has been a final judgment and is no longer subject to appeal; and the legal doctrine meant to bar (or preclude) continued litigation of a case on same issues between the same parties. In this latter usage, the term is synonymous with "issue preclusion". In the case of res judicata, the matter cannot be raised again, either in the same court or in a different court. A court will use res judicata to deny reconsideration of a matter.
Excerpt from Cornell University, a private and statutory Ivy League research university in Ithaca, New York. Founded in 1865. https://www.law.cornell.edu/wex/res_judicata
Generally, res judicata is the principle that a cause of action may not be relitigated once it has been judged on the merits. "Finality" is the term which refers to when a court renders a final judgment on the merits.
Res judicata is also frequently referred to as "claim preclusion," and the two are used interchangeably throughout this article.
Breaking Down the Concept
Claim preclusion can be best understood by breaking it down into two sub-categories:
example: Plaintiff P sues Defendant D on Cause of Action C, but P loses. P may not try for better luck by initiating a new lawsuit against D on C.
Merger - a winning plaintiff cannot re-sue a losing defendant on the same cause of action
example: Plaintiff P successfully sues Defendant D on Cause of Action C. P may not again sue D on C to try to recover more damages.
As illustrated in the merger example, a claim can have finality, even when the judge does not award damages. Thus even if a winning party believes he deserves more in damages than he received (or if he received no damages, he believes he deserves some damages), he is not able to sue on the same cause of action.
Policies of Preclusion
There is a litany of cases dealing with res judicata. Courts, often uphold the doctrine, and typically justify res judicata based on several polices:
avoiding inconsistent adjudication
Does Claim Preclusion Apply for Adjudication Not "On The Merits?"
"On the merits" refers to a judgment, decision, or ruling that a court will make based on the law, after hearing all of the relevant facts and evidence presented in court. Claim preclusion historically only referred to cases decided on the merits. However, the modern view taken by most jurisdictions is that a dismissal based on a failure to state a claim is also claim preclusive. Rule 12(b)(6) of the Federal Rules of Civil Procedure deals with a dismissal based on a failure to state a claim.
According, however, to Rule 41(b) of the Federal Rules of Civil Procedure, the following are not claim preclusive and are not considered an adjudication "on the merits":
a lack of jurisdiction
if the dismissal order does not state otherwise (i.e. a decision made "without prejudice" would not be claim preclusive")
Many jurisdictions also find that res judicata applies to a "dismissal for a failure to prosecute." This phrase refers to an involuntary dismissal of a plaintiff's claims when the plaintiff fails to comply with the court's orders in some ways. These dismissals, however, are highly reviewable by appellate courts to ensure that the trial court was not abusing its discretion.
The rules regarding unasserted counterclaims, however, have some nuance. While an unasserted permissive counterclaim is not precluded, an unasserted compulsory counterclaim, is precluded. There are 2 exceptions to this rule:
If the defendant wins an affirmative defense, then the defendant can counterclaim on the same facts
Some jurisdictions also follow the "Common Law Compulsory Counterclaim Rule." This rule states that if "Party A" fails to assert an available counterclaim during "Trial A," then "Party A" is precluded from suing in "Trial B" if granting relief of that action would nullify the judgment from "Trial A."
Alternative Techniques to Preclude Another Party’s Actions
In addition to bar and merger, there are two other techniques that courts look to which have the same effect on a cause of action as claim preclusion:
"Party A" cannot litigate a position when that position is inconsistent with "Party A's" earlier conduct which "Party B" has detrimentally relied upon
"Party A" cannot unfairly take factual positions in litigation that are inconsistent with previous positions that Party A had taken in prior judicial proceedings
Claim Preclusion and Adverse Parties
In judicial proceedings, claim preclusion only applies to adverse parties, it does not apply to co-parties (ex: a party that has been joined via Federal Rule of Civil Procedure 19 or Federal Rule of Civil Procedure 20). Contrast this rule with collateral estoppel (also known as "issue preclusion"), which applies to both co-parties and adverse parties.