Facts
The appellants [A.A.] and [B.A.] (sellers) and [C. AG] (buyer) concluded on 29 April 2008 a contract designated as 'Contrat de vendange', under which the sellers undertook to deliver the entire grape harvest of 82 vineyard plots (approx. 86'000 m2) for an initial period of ten years. The prices were based on the official tariff of the trade association of Valais wines. Art. 5 of the contract provided that the party not complying with the contract had to pay the other party an annual harvest compensation, calculated on the average of the three last harvests.
The 2010 harvest was in dispute. The buyer argued that the sellers had not delivered the entire quantity of grapes. The sellers countered that several plots could no longer be cultivated due to the termination of leases and the partial takeover by third parties, and that weather and fungal infestation had led to an exceptionally poor harvest.
On 27 July 2012 the sellers sued before the District Court of Leuk and Westlich-Raron for payment of CHF 76'888.20 plus interest as the purchase price. The buyer filed a counterclaim for a contractual penalty of, in its final form, CHF 173'463.95. The District Court obtained an expert opinion (20 May 2016, supplemented in 2016 and 2017) and on 9 May 2018 ordered the sellers to pay CHF 33'111.80 to the buyer. On appeal by the sellers, the Cantonal Court of Valais on 5 November 2019 set aside the judgment and ordered the buyer to pay CHF 76'888.20 less CHF 49'160.75, plus interest.
By civil law appeal, the sellers requested that the claim be fully upheld, the counterclaim dismissed, and, in the alternative, that the matter be remanded. The buyer requested that the appeal be dismissed. The lower court waived its comments.
The lower court established binding findings that in 2010 the sellers delivered 24'415 kg of grapes and withheld 55.5 % of the amount owed (target delivery quantity 54'847 kg). The contractual penalty was set at half of a target value of CHF 177'155.80, i.e. CHF 88'577.90, and reduced in proportion to the 55.5 % non-performance to CHF 49'160.75.
Considerations
The Federal Supreme Court reviews the civil law appeal under Art. 95 and 96 FSCA. The factual findings of the lower court are binding (Art. 105 para. 1 FSCA), unless they are manifestly incorrect, that is arbitrary (Art. 97 para. 1 FSCA). The parties must clearly and substantiably demonstrate that this is the case, and may only raise new facts if they were properly introduced (Art. 99 para. 1 FSCA). An assessment of evidence may only be corrected where it is manifestly untenable; mere appellate criticism is not sufficient.
The complaints concerning the assessment of evidence and the target delivery quantity fail. The sellers merely presented their own assessment of the documents. The lower court based its finding of non-performance on the expert opinion, the missing receipts and the collapse of the harvest. The assertion that the deduction of 15 % already included the fungal infestation was also not sufficiently substantiated. The complaint regarding the wrong allocation of the burden of proof is moot, as the non-delivery is binding established (cf. BGE 141 III 241 E. 3.2). The complaints alleging violation of Art. 97 CO and Art. 160 para. 1 CO rely on a set of facts that deviates from the binding findings and are therefore irrelevant.
In the case of partial non-performance, the contractual penalty is owed in proportion to the unperformed part, irrespective of a reduction under Art. 163 para. 3 CO (judgment 4A_653/2016 of 20 October 2017 E. 5.2.2). A cumulation of performance and penalty under Art. 160 para. 1 CO does not arise, and accepting the partial performance does not constitute a waiver of the full…