How To Prove A California Unilateral Mistake Defense

In California, a defense of Unilateral Mistake is defined as:
A unilateral mistake occurs when one party is mistaken about a material fact in a contract.
It simply means:
When one party to a contract has the wrong understanding of a material fact.
There are 4 elements of the defense:
- Element 1. The defendant was mistaken as to a material fact regarding a contract. The defendant misunderstood an important detail about the contract, which led them to make a decision based on incorrect information, potentially allowing them to argue that the contract should not be enforced due to this mistake.
Facts that might support this element look like:
* The defendant believed that the contract included a specific clause regarding payment terms, which was not present in the final document.
* The defendant was under the impression that the property being sold was free of liens, but later discovered it was encumbered.
* The defendant relied on a verbal assurance from the plaintiff that certain repairs would be completed before the contract was signed, which was not fulfilled.
* The defendant mistakenly thought that the contract was for a one-year lease, while it was actually for a two-year term.
* The defendant was unaware of a critical change in the law that affected the enforceability of the contract terms at the time of signing. - Element 2. The plaintiff knew defendant was mistaken and used the mistake to take advantage of the defendant. In a unilateral mistake defense, this element means that the person who made the mistake was aware that the other party was wrong and then exploited that error for their own benefit, which is considered unfair and can affect the validity of the agreement.
Facts that might support this element look like:
* The plaintiff was aware that the defendant had miscalculated the value of the contract before finalizing the agreement.
* The plaintiff intentionally withheld information that would have clarified the defendant’s misunderstanding of the terms.
* The plaintiff had previously discussed the correct figures with the defendant but chose to exploit the error instead.
* The plaintiff’s actions demonstrated a clear intent to benefit from the defendant’s mistake, as evidenced by their subsequent conduct.
* The plaintiff failed to correct the defendant’s misunderstanding despite having the opportunity to do so prior to the agreement. - Element 3. The defendant’s mistake was not caused by the defendant’s excessive carelessness. In a Unilateral Mistake Defense, this element means that the defendant’s error happened without being overly careless; they took reasonable steps to avoid mistakes, showing that their misunderstanding wasn’t due to a lack of attention or caution on their part.
Facts that might support this element look like:
* The defendant conducted thorough research before entering into the agreement, demonstrating a reasonable level of diligence.
* The defendant sought advice from a qualified professional, who confirmed the accuracy of the information provided.
* The circumstances surrounding the transaction were complex, making it difficult for the defendant to foresee the mistake.
* The defendant promptly notified the other party upon discovering the mistake, indicating a lack of negligence.
* The defendant had no prior history of similar mistakes, suggesting a consistent pattern of careful behavior. - Element 4. The defendant would not have agreed to enter into the contract if defendant had known about the mistake. The defendant wouldn’t have signed the contract if they had known about the mistake, meaning they were misled and wouldn’t have agreed to the deal if they had the correct information.
Facts that might support this element look like:
* The defendant was unaware of the pricing error and believed the contract terms were fair and reasonable based on the information provided.
* The defendant had previously negotiated similar contracts at higher prices, indicating a different expectation of value.
* The defendant expressed concerns about the contract’s terms before signing, highlighting a desire for clarity and accuracy.
* The defendant would not have committed resources to fulfill the contract if they had known the terms were based on a mistake.
* The defendant’s business model relies on accurate pricing, and a mistake would have led to financial losses that were unacceptable.
(See California Civil Jury Instructions (CACI), No. 330. California Civil Code Section 1689. White v. Berrenda Mesa Water Dist., 7 Cal. App. 3d 894 – Cal: Court of Appeal, 5th Appellate Dist. 1970.)
If you’re representing yourself in court and plan to assert a Defense of Unilateral Mistake, having a strong strategy is essential. A Personal Practice of Law at Courtroom5 will guide you through each phase of your case, helping you decide what to file and prepare legal documents backed by thorough research and analysis of the facts. Equip yourself with the tools you need to effectively present your Defense of Unilateral Mistake.
Prove Your CA Unilateral Mistake Defense
U.S. Civil Cases Only