An expert report commissioned by one party is not, in principle, enough to found a French judge’s decision, even when the opponent took part in the expert’s work. The reported decision of the First Civil Chamber of the Cour de cassation (the French supreme court for civil and commercial matters) of 15 October 2025 confirms that rule and marks its limit: where the expert’s findings concern an established fact that the parties do not dispute, the judge may rely on that report alone. For anyone commissioning a valuation for use in litigation, the decision suggests, by transposition, separating what the report finds from what it estimates.
The facts
On 15 June 2018, an individual bought a used vehicle from a company. On 30 April 2019, she resold it to a buyer, the transfer certificate stating a mileage of 141,000 km.
On 8 April 2021, a roadworthiness test cast doubt on that mileage. The buyer’s insurer then had a private expert appraisal (expertise amiable) carried out “au contradictoire” of the seller, that is on an adversarial basis: the insurer gave the instruction, but the seller was given the opportunity to take part. The appraisal concluded that the mileage had been altered before the sale made by the seller, since the vehicle already showed a higher mileage at the roadworthiness tests of 25 August 2017 and 4 June 2018.
On 24 November 2022, the buyer brought proceedings before a local court (tribunal de proximité) for rescission of the contract and refund of the price. By a judgment of 11 January 2024, the Aulnay-sous-Bois local court rescinded the sale and ordered the seller to refund the price in full. The seller appealed to the Cour de cassation. In her view, the judge may base a decision on an expert report drawn up at the request of one party, even an adversarial one, only if its conclusions are corroborated by other evidence; by ruling on the strength of the buyer’s private report alone, the court had breached article 16 of the French Code of Civil Procedure, which secures the adversarial principle.
The decision
The Cour de cassation dismissed the appeal (Cass. 1re civ., 15 October 2025, appeal no. 24-15.281, reported decision).
It stated the rule and its limit in a single sentence: “While the judge cannot base his decision exclusively on a non-judicial expert report, even an adversarial one, drawn up at the request of one party, it is otherwise if the expert’s findings and conclusions concern a fact that is established and not disputed by the parties” (translated from the French).
It then applied it to the case. The local court had found that the alteration of the mileage before the sale, as found by the appraisal, was not contested by the parties, who agreed that the seller had herself been deceived when she bought the vehicle from the original seller. Accordingly, “the court was entitled to rescind the sale on the basis of the difference between the actual mileage and the mileage shown on the transfer certificate and the non-conformity of the vehicle” (translated from the French).
The underlying rule, which the Court restates here, goes back to a decision of the Mixed Chamber of 28 September 2012 (appeal no. 11-18.710). The decision calls for two observations. The adversarial character of a private appraisal does not give it the weight of a court-ordered appraisal (expertise judiciaire): the rule applies “even” when the other party took part in the expert’s work. And the exception does not depend on the form of the appraisal, but on what it concerns: a fact that is established and that the parties do not dispute.
What this changes for valuation
Fact and opinion do not share the same fate. The decision concerns a material fact, a mileage, and says nothing about the value of a property. Applied to property valuation, it suggests separating two layers in the report: the findings (measured floor area, condition of the building, defects observed, planning zone, current lease, prices of the comparable sales) and the valuation itself (choice of comparables, deductions, value adopted). The opponent may accept the former; the latter is rarely accepted. It is the judge who finds, from what the parties argue, that a fact is not disputed; the report makes that finding easier when it sets out each observation separately, with its source. The Charte de l’expertise en évaluation immobilière (the French property valuation charter) in fact requires the report to distinguish clearly between facts and opinions and to list the documents provided and used (6th edition, November 2025, Title II, chapter 10, § 10.2).
A disputed value must be corroborated. As soon as the other party contests the figure, a report drawn up at the request of one party alone falls back under the general rule, even if the opponent took part in the expert’s work. On 1 April 2026 the Commercial Chamber made clear that corroboration may come from documents annexed to the report, provided they are not the expert’s own work (Private expert report: its own annexes can corroborate it). The two decisions fit together: the 2025 decision allows the judge to rely on the report alone for an established fact nobody disputes, the 2026 decision shows how to support what remains contested. In a sale dispute, the existence of a nuisance or a defect may thus be accepted on both sides, while the discount it causes remains in dispute and must rest on references (Seller’s fraud: claiming the excess price without annulment).
Involving the opponent remains useful, without changing the nature of the report. Inviting the other party to the inspection allows that party to submit observations and may bring out the points of agreement. But an appraisal commissioned by one party, even when carried out on an adversarial basis, is not a joint private valuation (expertise amiable conjointe) within the meaning of the Charte, which requires a joint request by two or more parties (Title I, § 1.1). An expert chosen by mutual agreement under a clause of the contract falls under another reported decision, of 8 January 2026: Contractual expert appraisal: the judge may rely on it alone.
The report keeps a record of what was submitted. Date of the inspection, persons present, documents provided, observations received: these entries show what the other party was able to examine and what it did not contest (What a French property valuation report must contain).
What the valuer takes from it
- A private appraisal, even one carried out on an adversarial basis, remains a party’s appraisal: on its own, it is not enough on a disputed point.
- The judge may rely exclusively on such a report where its findings and conclusions concern an established fact that the parties do not dispute.
- The report separates the findings, each with its source, from the valuation.
- Value, which the opponent usually contests, remains subject to the general rule: the report alone is not enough, and other evidence must support it.
- The format, single-party, joint, provided for by contract or court-ordered, is chosen at the start of the assignment.
Further reading
The Court expert, joint valuation and litigation support in France page describes the assignments, how they are conducted and their fees. The guide Producing a valuation in a French court: which format to choose? and the glossary entries expertise amiable conjointe, expertise en évaluation immobilière and assistance à expertise complement this article. On the contractual appraisal: Contractual expert appraisal: the judge may rely on it alone. On the same theme: Private expert report: its own annexes can corroborate it and What a French property valuation report must contain. The decision is available on Légifrance.
What next
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