CACI No. 331. Affirmative Defense - Bilateral Mistake
Judicial Council of California Civil Jury Instructions (2025 edition)
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331.Affirmative Defense - Bilateral Mistake
[Name of defendant] claims that there was no contract because both
parties were mistaken about [insert description of mistake]. To succeed,
[name of defendant] must prove both of the following:
1. That both parties were mistaken about [insert description of
mistake]; and
2. That [name of defendant] would not have agreed to enter into this
contract if [he/she/nonbinary pronoun/it] had known about the
mistake.
If you decide that [name of defendant] has proved both of the above, then
no contract was created.
New September 2003
Directions for Use
This instruction does not contain the requirement that the mistake be material to the
contract because the materiality of a representation is a question of law. (Merced
County Mutual Fire Insurance Co. v. State of California (1991) 233 Cal.App.3d
765, 772 [284 Cal.Rptr. 680].) Accordingly, the judge would decide whether an
alleged mistake was material, and that mistake would be inserted into this
instruction.
If the mistake is one of law, this may not be a jury issue.
Sources and Authority
• When Consent Not Free. Civil Code section 1567.
• Consent Obtained by Fraud. Civil Code section 1568.
• Mistake. Civil Code section 1576.
• Mistake of Fact. Civil Code section 1577.
• Mistake of Law. Civil Code section 1578.
• Rescission of Contract. Civil Code section 1689.
• “A mistake of fact may be urged as a defense to an action upon a contract only
if the mistake is material to the contract.” (Edwards v. Lang (1961) 198
Cal.App.2d 5, 12 [18 Cal.Rptr. 60].)
• “A ‘mistake’ within the meaning of subdivision (b)(1) of section 1689 of the
Civil Code can be either one of fact or of law. ‘Generally a mistake of fact
occurs when a person understands the facts to be other than they are . . . .’
When both parties understand the facts other than they are, the mistake
necessarily is mutual and thus becomes a basis for rescission.” (Crocker-Anglo
146
Nat’l Bank v. Kuchman (1964) 224 Cal.App.2d 490, 496 [36 Cal.Rptr. 806],
internal citations omitted.)
• “[T]o warrant a unilateral rescission of a contract because of mutual mistake, the
mistake must relate to basic or material fact, not a collateral matter.” (Wood v.
Kalbaugh (1974) 39 Cal.App.3d 926, 932 [114 Cal.Rptr 673].)
• “Where, as here, the extrinsic evidence is not in conflict, the determination of
whether a mutual mistake occurred is a question of law.” (Hess v. Ford Motor
Co. (2002) 27 Cal.4th 516, 527 [117 Cal. Rptr. 2d 220, 41 P.3d 46].)
• “Ordinary negligence does not bar a claim for mutual mistake because ‘ “[t]here
is an element of carelessness in nearly every case of mistake . . . .” ’ ‘Only
gross negligence or ‘preposterous or irrational’ conduct will [bar] mutual
mistake.’ ” (Thrifty Payless, Inc. v. The Americana at Brand, LLC (2013) 218
Cal.App.4th 1230, 1243 [160 Cal.Rptr.3d 718], internal citation omitted.)
• “Where parties are aware at the time the contract is entered into that a doubt
exists in regard to a certain matter and contract on that assumption, the risk of
the existence of the doubtful matter is assumed as an element of the bargain.”
(Guthrie v. Times-Mirror Co. (1975) 51 Cal.App.3d 879, 885 [124 Cal.Rptr
577].)
Secondary Sources
1 Witkin, Summary of California Law (11th ed. 2017) Contracts, §§ 257-276
17 California Forms of Pleading and Practice, Ch. 215, Duress, Menace, Fraud,
Undue Influence, and Mistake, §§ 215.50-215.57, 215.140 (Matthew Bender)
9 California Points and Authorities, Ch. 92, Duress, Menace, Fraud, Undue
Influence, and Mistake, § 92.90 et seq. (Matthew Bender)
27 California Legal Forms, Ch. 77, Discharge of Obligations, § 77.350 (Matthew
Bender)
1 Matthew Bender Practice Guide: California Contract Litigation, Ch. 8, Seeking or
Opposing Equitable Remedies in Contract Actions, 8.24
1 Matthew Bender Practice Guide: California Contract Litigation, Ch. 16, Attacking
or Defending Existence of Contract - Mistake, 16.08[1], 16.09, 16.11, 16.18
CONTRACTS CACI No. 331
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© Judicial Council of California.
