Estoppel is a defense in a variety of legal actions that happen in divorce. Estoppel can arise by what is called "acts and declarations," when one party by his or her action or statements deliberately induces another to alter his or her position to that person’s detriment. For example, estoppel in pais means the doctrine that a person’s conduct, including his duty to speak, may preclude from later asserting a right he otherwise would have had. Or, for example, promissory estoppel happens when one party relies on the promise of another to his or her detriment.
In divorce appeals, the doctrine of estoppel may appear as judicial estoppel, which is also known as estoppel by inconsistent positions. Judicial estoppel, which courts invoke frequently in divorce appeals, protects the judicial system from what one judge termed "chameleonic litigants." In this, a party is precluded from making a contention contrary to one he made in an earlier legal proceeding. In one divorce appeal in New York, for example, the court applied judicial estoppel against a husband who argued that he had an interest in his wife’s farm when in an earlier action involving a third-party creditor against him he had denied any interest in the property.
Collateral estoppel, which is similar to judicial estoppel, bars relitigation of issues that have already been tried. Collateral estoppel means that the a decided issue cannot be relitigated by the same parties in future court actions. In short, what’s done is done. In a divorce, collateral estoppel in general precludes relitigation of a marital property settlement after an equitable distribution.
In family law, equitable estopple finds application in paternity cases, where it holds that a man who presents himself as the father of a child may not change his mind and may in fact be held liable for support of a child borne to his wife but not biologically his. Equitable estoppel involves an element of detrimental reliance on the part of the party charging it, as in the case of a man party seeking to have a man who believed to his father named his father.
Estoppel, in its forms, rests on the doctrine of res judicata, a Latin term meaning "thing adjudged."
Res judicata means that the final judgment ends the case, and it bars subsequent action involving the same claim. This rule acts stops a party who, unhappy with the outcome of his "day in court," attempts to relitigate a case with the same cause for action. Its application bars attempts to litigate a case by a dissatisfied party who might attempt to bring identical causes for action to court in another court.
In a divorce, res judicata is a procedural defense against attacking a separation agreement after a divorce case has ended. When a court has ruled that a separation agreement is valid, the party who seeks to attack it after a decision and judgment has already had his or her "day in court."
The rule of res judicata does not apply to, for example, a motion to appeal child support due to change in circumstances, nor does apply to appropriate appeals.
See also Collateral Estoppel; Affirmative Defense; Res Judicata