Also known as:mistake and restitution · mistake · restitution · unjust enrichment
Written by attorneys · grounded in primary & secondary sources — see below
A body of principles addressing when a party's erroneous belief about a material fact permits avoidance or reformation of a transaction and recovery of benefits conferred through restitution. The doctrine allocates risk of mistake based on agreement, conscious ignorance, or judicial fairness and measures restitution by the value of benefits received or expenses incurred.
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Cases
Statutes
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Common Law
How it applies
Common Examples
6
Mutual Mistake Survives Deed Merger
Luke Latham sold waterfront land to Legacy Motors under a contract describing the parcel as buildable within seventy-five feet of the water. Both parties believed local zoning permitted that setback. After closing, Legacy discovered the actual requirement was two hundred fifty feet. Legacy sued for rescission and restitution of the purchase price. The court held that mutual mistake concerning a basic assumption of the exchange survived merger of the contract into the deed and permitted avoidance plus restitution.
Relation Back Based on Party Mistake
Lola Langley sued a corporation she believed operated the warehouse where she was injured. After the limitations period, she learned the correct entity was a related but distinct company. She moved to amend under Rule 15(c). The court allowed the amendment because the proper defendant knew or should have known the action would have been brought against it but for the mistake in identity, satisfying the relation-back requirements.
Prior Act Shows Absence of Mistake
Lamar Lewis was charged with possessing a controlled substance. He claimed he accepted the package by mistake, believing it contained legal supplements. The prosecution offered evidence that Lewis had previously received and distributed identical mislabeled packages. The court admitted the evidence under Rule 404(b)(2) to prove absence of mistake rather than character.
Conscious Ignorance Allocates Mistake Risk
Landon Long contracted to buy a vintage car from Lance Lee after inspecting it only by flashlight. Long knew the engine might have undisclosed defects but treated his limited knowledge as sufficient. When major mechanical problems surfaced, Long sought rescission. The court held that Long bore the risk of mistake under Restatement section 154(b) because he was aware of his limited knowledge yet proceeded, barring restitution.
Burden on Mistake in Will Contest
Leo Lynch offered a will for probate. A contestant alleged the testator signed under a mistake about the identity of a beneficiary. Under Uniform Probate Code section 3-407 the contestant bore the burden of establishing mistake. The court required the contestant to produce prima facie evidence of the mistake before shifting any burden back to the proponent.
Mistake Negatives Required Mens Rea
Lakeshore Industries shipped goods to a buyer who believed the contract required payment only upon inspection. The buyer refused payment after discovering defects. Charged with theft by deception, the buyer asserted mistake of fact. The court instructed the jury that if the mistake negated the purpose or knowledge required for the offense, acquittal was required under Model Penal Code section 2.04(1)(a).
Common questions
Frequently Asked
5
When does mutual mistake permit rescission and restitution in a real-estate contract after closing?+
Mutual mistake concerning a basic assumption of the exchange survives merger of the contract into the deed. The buyer may avoid the deed and recover the purchase price when both parties shared the same erroneous belief about a material fact such as zoning or boundaries.
What must a party show to bear the risk of mistake under Restatement section 154(b)?+
A party bears the risk when it is aware at contracting that it has only limited knowledge about the facts to which the mistake relates yet treats that limited knowledge as sufficient. Conscious ignorance prevents later avoidance or restitution.
How does Rule 404(b)(2) permit evidence of other acts to prove absence of mistake?
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Evidence of other crimes wrongs or acts may be admitted to show absence of mistake or lack of accident. The prosecution must give notice in criminal cases and the court must still conduct Rule 403 balancing.
What burden does a will contestant carry when alleging mistake under Uniform Probate Code section 3-407?+
The contestant must establish lack of testamentary intent or capacity undue influence fraud duress mistake or revocation. The proponent first bears the burden of due execution and the contestant then carries the ultimate burden of persuasion on mistake.
When does a mistake of fact or law serve as a defense under Model Penal Code section 2.04(1)(a)?+
Ignorance or mistake is a defense if it negatives the purpose knowledge belief recklessness or negligence required to establish a material element of the offense. The defense is unavailable if the defendant would still be guilty of another offense under the facts as supposed.
Criminal Law & ProcedureGeneral principles · Justification and excuseUBEFoundational