Município de Mariana v BHP: Court of Appeal refuses permission to appeal liability findings

The Court of Appeal has refused BHP Group permission to appeal the High Court's findings of liability arising from the collapse of the Fundão Dam in Brazil on 5 November 2015 — one of the most catastrophic environmental disasters in South American history. The decision, handed down on 6 May 2026 ([2026] EWCA Civ 502), marks a significant moment in litigation involving over 600,000 Brazilian claimants and costs exceeding £300 million.

The underlying Stage 1 liability judgement of O'Farrell J ([2025] EWHC 3001 (TCC)) was reached after a trial spanning 50 hearing days between October 2024 and March 2025. The dam, owned and operated by Samarco Mineração SA — a joint venture between Vale S.A. and BHP Brasil Ltd — released over 40 million cubic metres of iron ore tailings upon collapse, killing 19 people and causing devastation across more than 600 kilometres of the Doce River basin. O'Farrell J found BHP strictly liable as a polluter under Brazilian environmental law and also liable on a fault basis.

BHP advanced five grounds of appeal, grouped into strict liability, fault-based liability, and three limitation grounds. Cutting across all of them was an overarching submission that the trial judge had failed to engage with BHP's case, constituting a serious procedural irregularity under CPR 52.21(3)(b). Lord Justice Fraser, with whom Lord Justice Lewison agreed, rejected that framing root and branch.

Drawing on settled appellate principles from FAGE UK Ltd v Chobani [2014] EWCA Civ 5, Volpi v Volpi [2022] EWCA Civ 464, and McGraddie v McGraddie [2013] UKSC 58, the court reaffirmed that an appellate tribunal must assume, absent compelling reason, that a trial judge has considered all evidence before her, even where specific documents or arguments are not expressly addressed in the judgement. A failure to mention a particular piece of evidence does not establish a failure to consider it. The court was pointed in its assessment: what BHP characterised as procedural irregularity amounted, on analysis, to nothing more than the judge preferring the claimants' case.

The alleged "concession" by the claimants' environmental law expert, Professor Sarlet — said to undermine the judge's application of a multifactorial approach to indirect polluter liability — was examined and rejected. Fraser LJ found no formal experts' agreement on the point, that the transcript did not support the characterisation advanced, and that the trial judge had expressly addressed and dismissed the same submission in closing. He described the repeated invocation of the word "concession" in BHP's skeleton as particularly regrettable.

The court also declined to accept that, in the context of Brazilian law — a civil code jurisdiction with Portuguese-language sources rooted in the Roman-Germanic tradition — there was any greater scope for appellate interference than with domestic findings of fact. Quite the reverse: the appellate court acknowledged itself to be at a significant disadvantage compared to a trial judge who had heard extensive oral evidence from Brazilian law experts across seven hearing days.

On the limitation grounds, BHP's contention that brevity of reasoning in the judgement signalled procedural irregularity was similarly dismissed. Fraser LJ observed that concision in a judgement exceeding 100,000 words and 1,129 paragraphs reflects proportionate judicial economy, not a failure of engagement.

One ground proceeds. O'Farrell J herself granted permission on the narrow question of whether the trial judge was correct to order BHP to pay interest on costs at 1% over base rate, reflecting the claimants' litigation funding arrangements. The claimants' costs stood at approximately £189 million as at January 2026. The court granted expedition of that appeal, provisionally listed for October 2026, noting the significant sums potentially at issue and the benefit to both parties of early resolution.

A Stage 2 trial addressing quantum and other outstanding issues is scheduled for 2027–2028.