Prevalent Probability and Universality of Risk in Marine Insurance: Commentary on Supreme Court Judgment (Plenary Session) No. 1130/2026 of 13 July

Supreme Court, First Chamber (Plenary Session). Judgment No. 1130/2026, of 13 July. Appeal No. 9733/2021. Presiding Judge: His Excellency Mr Fernando Cerdá Albero. ROJ: STS 3135/2026. ECLI:ES:TS:2026:3135.

Facts

Millenium Trading Invest, S.A. had insured the tuna vessel Txori Urdin under a hull policy taken out with Royal & Sun Alliance, Mutua de Riesgo Marítimo and Mapfre. Initially, the cover included the Institute Fishing Vessel Clauses and the Institute Additional Perils Clauses for Hulls. However, following the loss of the vessel’s classification, the parties agreed to reduce the scope of the cover, limiting it to the former and, consequently, to a named perils system.

On 25 September 2015, the vessel sank as a result of a leak, the cause of which could never be determined. Several factors shaped the course of the legal proceedings: the weather and sea conditions were favourable; the incident occurred in broad daylight whilst the crew were on the alert due to the presence of schools of fish; neither the radar nor the sonar detected any objects in the water; and the depth at which the ship sank prevented any inspection of the wreck.

Commercial Court No. 1 of A Coruña dismissed the claim on the grounds that the insured had not demonstrated that the incident constituted a risk covered by the policy. The Provincial Court of Appeal overturned that decision, holding that the principle of universality of risk applied and finding the insurers’ evidence insufficient to prove that the risk was excluded.

The Plenary Session of the Supreme Court upholds the first ground of the extraordinary appeal on the grounds of a procedural irregularity, sets aside the appeal judgment and, ruling on the matter itself in accordance with Final Provision 16.7 of the Civil Procedure Act (LEC), upholds the judgment at first instance, without ruling on the four grounds of the appeal on points of law.

Fundamentals of Law

1. Exceptional review of the assessment of the evidence

The judgment begins by reiterating a well-established principle: the assessment of evidence is a matter for the courts of first instance and does not, in principle, constitute a matter subject to review on appeal or by way of an extraordinary appeal on grounds of procedural irregularity.

However, it reiterates the principle already set out in Supreme Court Judgment 64/2026 regarding the exceptional circumstances in which the Supreme Court may review that assessment: where there is a manifest error of fact, or where the decision is the result of arbitrary or manifestly irrational reasoning and, as a result, infringes the right to effective judicial protection.

It is worth noting a point of immediate practical relevance set out in the judgment itself: Article 469(1)(4) of the Civil Procedure Act (LEC), the legal provision relied upon by the appellants, has now been repealed, and this procedure is currently set out in Article 477(5) of the LEC following the reform introduced by Royal Decree-Law 5/2023 of 28 June.

It then sets out the criteria that must guide the assessment of expert evidence in accordance with the rules of sound judgement: the expert’s qualifications; any circumstances that might compromise their objectivity; the methodology employed and its acceptance by peers within the scientific or professional community; the principle of the concurring majority; the manner in which the subject matter of the expert report is recognised in light of the spatial and temporal conditions under which it was carried out; and the internal consistency of the report. It also points out that these rules are breached, amongst other scenarios, when the court, in the absence of conflicting expert opinions, reaches conclusions on the basis of the evidence submitted that differ from those set out in those opinions.

2. Probability of prevalence as the standard in civil proceedings

The most significant procedural contribution of the judgement is the assertion that civil proceedings do not require absolute certainty, but rather a preponderance of the evidence.

The Plenary Session criticises the Provincial Court for rejecting the insurers’ expert reports on the grounds that they were based on ‘mere conjecture and probabilities that cannot be regarded as proven’. The Chamber draws a clear distinction between conjecture and probability: whilst the former does not meet the standard of proof, the latter may do so when it constitutes the most probable explanation of the facts and there is no alternative hypothesis of similar strength.

In this case, having ruled out grounding and weather conditions, the only question was whether the leak could have been caused by the vessel colliding with a floating object adrift or with any derelict property. On this point, the only evidence available was the expert reports provided by the insurers, drawn up using physical calculations and computer modelling, which ruled out that hypothesis. The insured party did not submit any expert evidence nor did they offer an alternative, technically sound explanation.

The Court states that the inability to inspect the wreck is a factor that must be taken into account when assessing the expert report, as it affects the manner in which the subject matter is examined; however, it does not in itself justify the rejection of technically sound reports. If the Court of Appeal considered that they did not meet the standard of prevailing probability, it should have explained why. The Chamber adds a pertinent temporal nuance: what was relevant was not the condition of the vessel in the preceding months – as established by the technical inspections on which the appeal judgment was based – but its condition at the very moment the leak occurred.

3. Universality and specificity of risk

It is here that the judgement makes its most significant contribution to maritime insurance law.

The Court begins with an overview of the historical development of the principle of universality of risk. It points out that both Article 861(I) of the 1829 Commercial Code, in referring ‘generally to all accidents and risks at sea’, and Article 755(I)(14) of the current Code, which mentions ‘any other accidents or risks at sea’, used an open-ended clause that allowed all risks at sea not expressly excluded to be understood as included. It is from this historical formulation that the well-known principle derives, according to which risks not excluded must be deemed to be included.

However, the Plenary Session clarifies that this principle was never a rule concerning the burden of proof, but rather a substantive rule intended to determine the scope of cover where the contract did not expressly define the insured risks.

The Maritime Navigation Act maintains this principle solely on a supplementary basis. Articles 407.1, 417 and 429 are based on the freedom of contract, such that it is the parties who determine the risks covered, as emphasised in Section X of the preamble, which states that the insured risks are defined by agreement. Where the policy incorporates named-risk clauses, such as the Institute Fishing Vessel Clauses, the principle of universality ceases to apply and the cover is defined exclusively by the contract. The Chamber itself reserves a residual role for the principle: it would retain some significance, if at all, in relation to unknown risks not mentioned either in the list of included risks or in that of excluded risks.

The judgement adds a clarification of considerable interest: it reviews previous case-law on the principle of universality of risk and concludes that none of the decisions traditionally cited actually based their ratio decidendi on that principle, nor did they attribute any effects to it in relation to the burden of proof. In doing so, the Plenary Session definitively restores the principle to its original function as a historical and supplementary rule for defining the scope of cover.

Applying that doctrine to the case, the Court concludes that the insured proved that the vessel had sunk, but not that this was due to any of the risks expressly covered by clause 6 of the policy; consequently, the insured failed to prove the fact constituting the basis of their claim in accordance with Article 217(2) of the LEC.

4. Conclusion

Supreme Court Ruling 1130/2026 goes well beyond the scope of marine insurance. Together with Supreme Court Rulings 9/2026 and 64/2026, it establishes the ‘prevailing probability’ as the general standard in civil proceedings and defines more precisely the scope of judicial review of expert evidence. It will be difficult to reject a technically sound expert opinion on the mere grounds that it is expressed in probabilistic terms where there is no alternative hypothesis of comparable weight.

At the same time, it redefines the scope of the principle of universal cover under the Maritime Navigation Act, noting that its function is purely supplementary and that, where the parties have opted for a system of named risks, it is the contract itself – and not a general clause of cover – that determines the scope of the insurance cover.