Res Judicata and Collateral Estoppel (Preclusion)

The rules that stop a dispute from being litigated twice - claim preclusion, which bars a second suit on a claim that was or could have been decided, and issue preclusion, which bars re-arguing a specific issue actually decided, the elements of each, who is bound, the exceptions, and why "could have been raised" is the part that surprises people.

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What it means

Once a court has decided a dispute, the law treats that decision as final between the parties, and two related doctrines enforce that finality. Res judicata, now usually called claim preclusion, provides that a final judgment on the merits bars the same parties (and those in privity with them) from bringing a second suit on the same claim - and "the same claim" means the whole transaction or series of connected events, not merely the legal theories the first complaint happened to plead. A plaintiff who sued for breach of contract and lost cannot sue again for fraud on the same deal; a plaintiff who won damages for a car crash cannot return for the injuries that were left out. The doctrine bars claims that were actually decided and claims that could have been raised in the first action, which is the feature that catches people who split their case, hold something back, or sue in a court that could not hear all of it.

Collateral estoppel, or issue preclusion, is narrower and reaches further. It prevents a party from re-litigating a specific issue of fact or law that was actually litigated and necessarily decided in a prior case, even if the second case involves a different claim, provided the party against whom it is asserted had a full and fair opportunity to litigate the issue the first time. The requirements are strict: the issue must be identical, it must have been actually contested and decided rather than conceded or assumed, and the decision must have been essential to the judgment, not an aside. Modern law allows a stranger to the first case to use its result against a party who lost there - a plaintiff may rely on a finding made against the defendant in someone else's suit - but the reverse is never true: a person who was not a party to the first case, and had no chance to be heard, cannot be bound by it, because due process forbids it.

Both doctrines depend on a valid final judgment, and courts of one state and the federal courts must give the judgment of another the same preclusive effect it would have where it was rendered. A dismissal for lack of jurisdiction, improper venue or failure to join a party is not a judgment on the merits and precludes only the point decided; a voluntary dismissal without prejudice precludes nothing; a default judgment precludes the claim but, in most jurisdictions, no issue, since nothing was actually litigated. Settlements and consent judgments preclude what the parties agreed they would. A criminal conviction may be used to establish the underlying facts in a later civil suit by the victim, but an acquittal establishes nothing for civil purposes because of the different standard of proof. Preclusion is an affirmative defense that must be pleaded and is waived if it is not, and there are recognized exceptions - a change in the law, an intervening judgment, an issue of law in unrelated claims, a first forum whose procedures were too limited to be fair - that a court weighs before applying it.

Where this comes from

When people hire a lawyer for this

Preclusion is the reason a lawsuit has to be planned as a whole: every claim arising from the same events should be brought together, in a court that can hear all of them, or deliberately reserved with the court's leave, because what is left out is usually lost. A person who lost an earlier case - an administrative hearing, a small-claims trial, a family-court finding - should have a lawyer assess what that decision now prevents before filing anything new, and a defendant facing a second suit should raise the defense in the answer or lose it. The doctrines also cut the other way: a favorable finding in one case can be a powerful weapon in the next, and a lawyer who knows how to use it can shorten the second case considerably.

Worried about the cost? A lawyer can be hired for one part of a case only (limited-scope representation), may be paid from what a claim recovers (contingency fee), or may be free through a pro bono program or legal aid; a court can also waive its own filing fees.

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Related terms

Other entries in the same area of law, each written from the same primary sources.

• AppealThe review of a trial court's decision by a higher court - what can be appealed and when (the final-judgment rule and its exceptions), the notice of appeal and why missing it is fatal, what "standard of review" means and why most appeals are lost on it, preserving error at trial, the record and briefs, and what an appellate court can and cannot do with the result.
• Attorney-Client Privilege and Work ProductThe two protections that keep what a client tells a lawyer, and what a lawyer prepares for a case, from being forced into evidence - what the privilege covers and what it does not, who holds it and how it is waived, the crime-fraud exception, the separate and narrower work-product doctrine, and how each is asserted in discovery.
• Burden of Proof (Standards of Proof)Who has to prove what, and how convincingly, before a court will rule for them - the difference between the burden of production and the burden of persuasion, the three standards (preponderance of the evidence, clear and convincing evidence, beyond a reasonable doubt) and where each applies, presumptions that shift the burden, and why the burden decides cases where the evidence is in balance.
• Complaint and Answer (Pleadings)The documents that start a civil case and frame what it is about - what a complaint must contain, how a defendant answers it, what an admission, denial and affirmative defense each do, counterclaims and cross-claims, and what happens when a pleading is late, deficient or needs to be amended.
• Contempt of CourtThe court's power to punish disobedience of its own orders - the mechanism that makes a court order more than a piece of paper.
• Court Fee Waiver (In Forma Pauperis)How a person who cannot afford court filing fees asks the court to excuse them - the federal and state procedures, who usually qualifies, and what a waiver does not cover.
• Default JudgmentA judgment entered because the person sued did not respond in time - the way most consumer debt lawsuits actually end.
• DepositionSworn, recorded, out-of-court questioning of a witness by the opposing lawyer, before any trial.
• DiscoveryThe pre-trial process in which each side must hand over relevant evidence to the other.
• Expert Witness (Daubert and Frye)A witness allowed to give opinions rather than only facts because of specialized knowledge - who qualifies, the gatekeeping test a judge applies to the reliability of the method (Daubert in federal court and most states, Frye in the rest), the written report and deposition that precede trial, the difference between a retained expert and a treating professional, and why a case can be lost when its expert is excluded.
• Fee Agreement and RetainerThe engagement letter that sets what a lawyer will do and how they are paid - hourly, flat or contingent fees, retainers held in trust, costs, and what to do about a fee dispute.
• Injunction and Temporary Restraining OrderThe court orders that require a party to do or stop doing something rather than pay money - the three stages (temporary restraining order, preliminary injunction, permanent injunction), the four-factor test for emergency relief, the bond the applicant must post, how an order is enforced through contempt, and why a violated order is obeyed first and challenged second.
• Jurisdiction and VenueThe three questions every lawsuit has to answer before its merits can be heard - whether the court has power over this kind of case (subject-matter jurisdiction), power over this defendant (personal jurisdiction), and whether this is the right place within the system to bring it (venue) - what each requires, how each is challenged, and why a judgment entered without jurisdiction is void.
• Limited-Scope Representation (Unbundled Legal Services)Hiring a lawyer for one defined part of a legal matter - advice, drafting a document, or a single hearing - instead of the whole case, and the written agreement that sets the boundary.
• Mediation and ArbitrationTwo ways of resolving a dispute outside a trial that are constantly confused - one produces an agreement you can walk away from, the other a decision you generally cannot appeal.
• Motion to DismissA request to end a case at the outset on the basis that, even if everything alleged is true, it does not amount to a legal claim.
• Pro Bono Legal HelpFree legal work by volunteer lawyers - what the professional rules ask of lawyers, how people of limited means are matched with a volunteer, and why it is not the same as legal aid.
• Release and Settlement AgreementThe document that ends a claim by giving up the right to bring it - normally final, and normally broader than people expect.
• Representing Yourself (Pro Se)The right to conduct your own case without a lawyer - available in almost every civil court, and held to almost the same standards as a lawyer.
• Service of ProcessThe formal delivery of court papers that gives a court power over the person sued - and the step whose failure undoes more judgments than any other.
• Small Claims CourtA simplified court for lower-value disputes, designed to be used without a lawyer - and in some states lawyers are not allowed in it at all.
• Statute of LimitationsA deadline, set by statute, after which a legal claim can no longer be brought at all.
• SubpoenaA court-backed order to give evidence or hand over documents - enforceable against people who are not parties to the case at all.
• Summary JudgmentA ruling that decides a case, or part of one, without a trial because the essential facts are not genuinely in dispute.

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