estoppel – a bar that prevents one from asserting a claim or right that contradicts something they previously said, or contradicts known truth

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(16c) n.

1. A bar that prevents one from asserting a claim or right that contradicts what one has said or done before or what has been legally established as true.

2. A bar that prevents the relitigation of issues.

3. An affirmative defense alleging good-faith reliance on a misleading representation and an injury or detrimental change in position resulting from that reliance.   Cf. WAIVER (2). — estop, vb. [1]

1. A bar which stoppeth a person or closes up his mouth to allege or plead what actually may be the truth. 2 Coke, Littleton 352a.

A bar which precludes a person from denying or asserting anything to the contrary of that which has, in contemplation of law, been established as the truth, either by the acts of judicial or legislative officers or by his own deed or representations, express or implied. 28 Am J2d Estop § 1.

A waiver, being the intentional relinquishment of a known right, is consensual in nature and is distinguished from an estoppel which is not consensual, but is given effect to defeat the inequitable intent of the party estopped. Seavey v Erickson, 244 Minn 232, 69 NW2d 889, 52 ALR2d 1144.

The elements of estoppel by acts or representation are reliance by a person entitled to rely on the acts and representations, the misleading of such person, an d in consequence, a change of position to his detriment, so that the person responsible for the misleading will not be permitted to deny the truth of his own statements, express or implied. 29A Am J Rev ed Ins § 1009.

Although the terms “waiver” and “estoppel are not convertible, the distinction between the two terms is not entirely clear in insurance cases. Grantham v State Farm Mut. Auto Ins. Co. 126 Cal App 2d Supp 855, 272 P2d 959, 48 ALR2d 1088.
     See judicial estoppel; promissory estoppel; waiver. [2]

1. A prohibition imposed by law against uttering what may actually be the truth.

There are two classes of estoppel.  A person may be estopped by his own acts or representations (that is, not be permitted to deny the truth or significance of what he said or did) if another person who was entitled to rely upon those statements or acts did so to her detriment.  This type of estoppel i also known as equitable estoppel or estoppel in pais.  The second type of estoppel is legal estoppel. It includes matters of record such as marriage, divorce, judgments, and deeds, as well as the findings of a court.  estoppel must be distinguished from waiver, which the voluntary surrendering of a known right. 
     See collateral estoppel; judicial estoppel; promissory estoppel. [3]

     Excerpt from Lancelot Feilding Everest’s Everest and Strode’s Law of Estoppel 1 (3d ed. 1923):

     “‘Estoppe,’ says Lord Coke, ‘cometh of the French word estoupe, from whence the English word stopped; and it is called an estoppel or conclusion, because a man’s own act or acceptance stoppeth or closeth up his mouth to allege or plead the truth.’ [Co. Litt. 352a.] Estoppel may also be dehned to be a legal result or ‘conclusion’ arising from an admission which has either been actually made, or which the law presumes to have been made, and which is binding on all persons whom it affects. [4]

     Excerpt from John H. Wigmore’s “The Scientific Role of Consideration in Contract,” in Legal Essays in Tribute to Orrin Kip McMurray 641, 643 (Max Radin & Alexander M. Kidd eds., 1935):

     “In using the term ‘estoppel,’ one is of course aware of its kaleidoscopic varieties.  One reads of estoppel by conduct, by deed, by laches, by misrepresentation, by negligence, by silence, and so on.  There is also an estoppel by judgment and by verdict; these, however, obviously involve procedure.  The first-named varieties have certain aspects in common.  But these aspects are not always interpreted by the same rules in all courts. The institution seems to be flexible. [5]

Types of Estoppel:

equitable estoppel prevents a person from adopting a new position that contradicts a previous position maintained by words, silence, or actions —aka estoppel by conduct; estoppel in pais.

promissory estoppel a person may be bound to a promise (estopped to deny the promise) if another person was induced to take action on that promise to their own detriment.

estoppel by acquiescence arises from a party’s failure to respond to a claim within a reasonable time after receiving notice

estoppel by agreement – Estoppel based on the terms of a contract between the parties expressly or impliedly showing a mutual acceptance of certain facts or assumptions. Also termed estoppel by convention.

estoppel by contract – (1874) A bar that prevents a person from denying a term, fact, or performance arising from a contract that the person has entered into.

estoppel by deed – (1841) Estoppel that prevents a party to a deed from denying anything recited in that deed if the party has induced another to accept or act under the deed; esp., estoppel that prevents a grantor of a warranty deed, who does not have title at the time of the conveyance but who later acquires title, from denying that he or she had title at the time of the transfer. See AFTERACQUIRED-TITLE DOCTRINE. -Also termed estoppel by warranty.

The apparent odiousness of some classes of estoppel, chiefly estoppels by deed, seems to result not so much from the nature of an estoppel, as from the highly technical rules of real property law upon which it operated, and with which it was associated. Estoppels by record, indeed, stand upon a considerably higher footing than estoppels by deed . . . .” Lancelot Feilding Everest, Everest and Strode’s Law of Estoppel 10 (1923).

estoppel by election – (1906) The intentional exercise of a choice between inconsistent alternatives that bars the person making the choice from the benefits of the one not selected.

estoppel by laches – (1894) An equitable doctrine by which some courts deny relief to a claimant who has unreasonably delayed or been negligent in asserting a claim.

estoppel by misrepresentation – (1882) An estoppel that arises when one makes a false statement that induces another person to believe something and that results in that person’s reasonable and detrimental reliance on the belief.

estoppel by negligence – (1875) An estoppel arising when a negligent person induces someone to believe certain facts, and then the other person reasonably and detrimentally relies on that belief.  Cf. assisted misrepresentation under MISREPRESENTATION.

estoppel by representation – (1863) An estoppel that arises when one makes a statement or admission that induces another person to believe something and that results in that person’s reasonable and detrimental reliance on the belief; esp., equitable estoppel.

estoppel by silence – (1872) Estoppel that arises when a party is under a duty to speak but fails to do so. -Also termed estoppel by standing by; estoppel by inaction.

judicial est-ppel. (1886) Estoppel that prevents a party from contradicting previous declarations made during the same or an earlier proceeding if the change in position would adversely affect the proceeding or constitute a fraud on the court. Also termed doctrine of preclusion of inconsistent positions; doctrine of the conclusiveness of the judgment.

legal estoppel –  (1818) Estoppel recognized in law (as distinguished from equitable estoppel or estoppel in pais), such as an estoppel resulting from a recital or other statement in a deed or official record, and precluding any denial or assertion concerning a fact.

quasi-estoppel (1823) An equitable doctrine preventing one from repudiating an act or assertion if it would harm another who reasonably relied on the act or assertion.

technical estoppel (1802) 1. An estoppel arising from a matter of record or from a deed made by the party who is claimed to be estopped. 0 Estoppels by deed or by record are called “technical” because the rules of estoppel apply with certainty in appropriate cases. 2. COLLATERAL ESTOPPEL. See estoppel by deed.

estoppel-asserter. (1900) Someone who relied on an alleged misrepresentation and seeks to have the person who made the representation held liable for the resulting harm or loss. 0 The asserter must be the person to whom the misrepresentation was directly made. -Also termed estoppel-raiser.

estoppel certificate. (1897) l. A signed statement by a party (such as a tenant or a mortgagee) certifying for another’s beneht that certain facts are correct, such as that a lease exists, that there are no defaults, and that rent is paid to a certain date. 0 A party’s delivery of this statement estops that party from later claiming a different state of facts. 2. See WAIVER OF CLAIMS AND DEFENSBS.

estoppel-denier. (1900) Someone who allegedly made a misrepresentation to another and seeks to avoid liability for the misrepresentation and show that a contradictory statement is true. [1]


Patent-Related Estoppel:

assignee estoppel (1970) Patents. The equitable doctrine that bars the assignee of a patent from contesting the patent’s validity under some circumstances, as when the assignee seeks to avoid royalty payments, to void an assignment contract, or to mitigate damages related to the assignee’s fraudulent acquisition of the patent.  *  The doctrine prevents an assignee from simultaneously attacking and defending the validity of the same patent.

assignor estoppel (1959) Patents. Estoppel barring someone who has assigned the rights to a pa

tent from later attacking the patent’s validity.Westinghouse Elec. e5 Mfg. Co. v. Formica Insulation Co., 266 US. 342, 45 S.Ct. 117 (1924).  *  The doctrine was narrowed by Diamond Scientific Co. v. Ambico, Inc., 848 F.2d 1220 (Fed. Cir. 1988), in which the court held that in some circumstances equity may outweigh the public-policy reasons behind the estoppel doctrine.

marking estoppel (1973) Patents. Estoppel that prevents a party from asserting that a product is not covered by a patent if that party has marked the product with a patent number.  *  This type of estoppel has been questioned in recent years, and has been sharply limited by some courts.

prosecution-history estoppel – (1983) Patents. The doctrine limiting a patent-holder’s invocation of the doctrine of equivalents by eliminating from the claims those elements that the holder surrendered or abandoned during the prosecution of the patent. — aka estoppel on the record; file-wrapper estoppel.  See DOCTRINE 0F EQUIVALENTS.


Disclaimer: All material throughout this website is compiled in accordance with Fair Use.

[1]: Black’s Law Dictionary Deluxe Tenth Edition by Henry Campbell Black, Editor in Chief Bryan A. Garner. ISBN: 978-0-314-61300-4

[2]: Ballantine’s Law Dictionary with Pronunciations Third Edition by James A. Ballantine (James Arthur 1871-1949).  Edited by William S. Anderson.  © 1969 by THE LAWYER’S CO-OPERATIVE PUBLISHING COMPANY.  Library of Congress Catalog Card No. 68-30931

[3]:  Ballantine’s Law Dictionary Legal Assistant Edition
by Jack Ballantine 
(James Arthur 1871-1949).  Doctored by Jack G. Handler, J.D. © 1994 Delmar by Thomson Learning.  ISBN 0-8273-4874-6.


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