The decision made on February 21 2001 by the Cour de Cassation establishes the irrelevance of a non-excusable mistake committed by a party when it results from fraud on the part of the other contracting party.
The case at hand concerned a buyer who, after having purchased a building and business, claimed the nullity of the sale due to the seller's fraud. However, the Court of first instance had ruled against him as he, in his capacity as a professional, should have informed himself properly. Since he did not do so, his mistake is deemed non-excusable.
The Cour de Cassation then qualified this decision as follows. It held that, in general, fraudulent omission of facts, given that it has been well established, always makes the resulting mistake excusable. In other words, a mistake is only non-excusable, and thus cannot lead to the nullity of the contract, as long as it is spontaneous. It is, however, without influence, i.e. excusable, when it becomes neutralised by fraudulent behaviour of the other party. This is a general rule, which applies even in case of fraudulent non-disclosure by one of the parties, which relates to substantial facts for the conclusion of the contract.European Review of Private Law