Also known as: mistake · mistakes · mistaken · error
Written by attorneys · grounded in primary & secondary sources — see below
A belief that is not in accord with the facts. An erroneous belief about a material fact can prevent formation of mutual assent, supply a ground for rescission or reformation, negate an element of an offense, or permit relation back of an amendment.
Select any source to read its text and confirm it supports the definition.
Melissa Mills and Mosaic Retail signed a purchase agreement stating the warehouse roof was new. At closing the deed omitted any roof warranty. After transfer a storm revealed the roof was twenty years old. Because both parties shared the same erroneous belief about the roof's age and condition, the mutual mistake exception allowed Melissa to seek reformation despite the merger doctrine.
Madison Meyers sued the wrong corporate subsidiary for a slip-and-fall injury. Within the Rule 4(m) period the correct parent company knew the suit was intended for it but for the misnomer. The court permitted the amendment to relate back under Rule 15(c)(1)(C)(ii) because the parent should have known the action would have been brought against it but for the mistake in identity.
Miles Montgomery was convicted after the trial court gave an erroneous jury instruction on the elements of the charged offense. Defense counsel did not object at trial. On appeal the court examined the mistake under plain-error review because the instructional error affected substantial rights even though it was not brought to the trial court's attention.
Melanie Morris was charged with knowingly possessing stolen goods. The prosecution offered evidence that she had received similarly marked merchandise from the same supplier two months earlier and returned it after learning it was stolen. The court admitted the evidence under Rule 404(b)(2) to prove absence of mistake regarding the current shipment's status.
Malcolm McKinley contracted to sell rare equipment to Monarch Pharmaceuticals for one-tenth its market value after both parties used an outdated price list. Enforcement would have been unconscionable given the gross disparity. The court therefore refused to enforce the contract under the unilateral-mistake doctrine.
Meredith Maxwell entered land she believed was a public park because an outdated map showed a trail easement. The possessor had never induced the belief. Even though her mistake of fact was reasonable, she remained liable as a trespasser under the rule that a mistaken belief of law or fact does not negate intentional entry.
A mistake is a belief that is not in accord with the facts. This definition supplies the foundation for analyzing mutual mistake in contracts, mistaken identity in civil amendments, and absence of mistake in evidentiary rulings.
Supporting sources
Merger discharges contractual promises not embodied in the deed, but an exception preserves claims based on mutual mistake. A buyer may still sue or seek reformation when both parties shared the same erroneous belief about a material fact such as the condition of the property.
…that there can be no due compensation for its weakness in constitutional law. The foregoing discussion has shown, I think, how mistaken is the Court in implying that the Constitution has struck the balance in favor of the approach the Court takes. Ante , p. 479. Rather, precedent reveals that the Fourteenth Amendment in…
…question of liability is one of general law; and on that ground declined to decide the issue of state law. As we hold this was error, the judgment is reversed and the case remanded to it for further proceedings in conformity with our opinion. Reversed. MR. JUSTICE CARDOZO took no part in the consideration or decision…
…only final agency decisions arrived at after considered judgment. It also permits agencies an opportunity to correct their own mistakes
…her as an incident of the sale without regard to such testimony. Accordingly, the contention that the instruction was reversible error
…on notice of the danger of removal, such advice would significantly reduce the chance that the client would plead guilty under a mistaken premise. III In sum, a criminal defense attorney should not be required to provide advice on immigration law, a complex specialty that generally lies outside the scope of a criminal…
An amendment changing the party relates back when the new party knew or should have known that the action would have been brought against it but for the mistake concerning the proper party's identity, provided the notice and prejudice requirements are also met within the Rule 4(m) period.
Evidence of other crimes, wrongs, or acts may be admitted to prove absence of mistake or lack of accident when offered for a non-propensity purpose and its probative value is not substantially outweighed by unfair prejudice.
A unilateral mistake justifies relief when enforcement would be unconscionable or when the other party had reason to know of the mistake or caused it. The court may rescind or reform the contract rather than enforce the erroneous term.