Also known as: reasonable certainty · reasonably certain · reasonable certainty rule
Written by attorneys · grounded in primary & secondary sources — see below
A standard of definiteness requiring that essential terms, damages, identifying information, or anticipated harm be established without undue speculation so that a court or lawyer can fashion an appropriate remedy, enforce an obligation, or take protective action.
Renata Russo, a corporate counsel, learns that her client plans to release a defective product that will likely cause multiple deaths. She determines the risk meets the required threshold of certainty. Russo discloses limited information to regulators to stop the release. The disclosure is permitted because the facts establish the necessary level of certainty about impending harm.
Rosa Ruiz and Rocky Mountain Mining exchange signed emails that name the parties, describe the ore shipment, and fix the price and quantity. The writings omit only the delivery date. A court finds the essential promises sufficiently definite to satisfy the memorandum requirement. The contract is enforceable despite the missing detail.
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Rachel Ramirez executes a will that refers to an attached inventory of jewelry. The inventory existed at execution and is described by date and location in the will. The court holds the list is identified with the required definiteness. The jewelry passes under the will by incorporation.
Rebecca Ross agrees to buy solar panels from Raven Logistics. The emails omit a fixed per-panel price but show mutual intent to contract and repeated shipments at listed rates. A court finds a reasonably certain basis for remedy through the course of performance and market data. The contract is enforceable.
Police obtain a warrant for a man seen fleeing a robbery. The affidavit describes him as six feet tall, wearing a red jacket, and driving a white van with a specific license plate. The description supplies the required level of certainty. The warrant is valid even though the suspect's name is unknown.
Ruby Rivera buys a franchise after Ronald Reed misrepresents its revenue history. Rivera proves the false statements and calculates lost profits from comparable franchises. The court awards the difference between actual and promised earnings because the amount is shown with the required certainty. Recovery is not limited to out-of-pocket loss.
The injured party must show the fact and amount of loss with evidence that permits a reasonable estimate rather than pure speculation. Courts resolve doubts against the breaching party once some loss is established. Historical performance data or industry benchmarks can supply the necessary foundation.
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The same standard governs both measures. Reliance expenditures are usually easier to prove with certainty because they are out-of-pocket sums already incurred. Lost profits under the expectation interest require additional evidence such as past performance or comparable transactions.
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Disclosure is permitted when the lawyer reasonably believes the client will cause death or substantial bodily harm and the risk reaches the required level of certainty. The lawyer may reveal only the information necessary to prevent the harm. The rule balances confidentiality against the need to avert serious injury.
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A plaintiff may recover lost profits shown by evidence such as prior sales history, market data, or expert testimony that permits a reasoned calculation. Purely speculative projections are excluded. The award must also be reduced to present value when future losses are involved.
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…on the concept of public use.[^maj-19] Alternatively, petitioners maintain that for takings of this kind we should require a "reasonable certainty" that the expected public benefits will actually accrue. Such a rule, however, would represent an even greater departure from our precedent. "When the legislature's purpose is legitimate…