Beyond the model: What UK and German courts expect from economic experts in cartel damages litigation

This article first appeared in an issue of Thought Leaders 4 - Competition Law & Litigation 2025: Redefined, Reimagined, Recharched.

Introduction

Economic evidence often plays a central role in damages cases associated with infringements of competition law. This article identifies key principles for how UK and German judges receive and evaluate economic evidence. Our analysis focuses on major cartel damages judgments in both jurisdictions, including BritNed v ABB¹, Royal Mail & BT v DAF^2, Granville v LG³, Stellantis v Autoliv⁴ and London Array v Nexans⁵ in the UK, as well as the Sugar, Rail track and Trucks cartel cases in Germany.

Four key lessons emerge from our review:

• The purpose of economic evidence is to provide insights about how damage may have arisen: Methodology and results must therefore reflect underlying facts about how the analysed market functions;
• Robustness testing of data and methodology assumptions is critical;
• Expert independence is required - no advocacy;
• Economic evidence should be tailored to be understood by judges.

One size does not fit all: Tailoring models to the market and infringement details

UK and German courts prioritise clear and commercially grounded factual evidence over analysis misaligned with market realities. A model is useful only when it tests pre-specified hypotheses, aligns with how the market operated and survives rigorous sensitivity checks. Statistical significance alone is insufficient; the analysis must be realistic.

In Royal Mail & BT v DAF, the Competition Appeal Tribunal (CAT) questioned both the defendant’s and claimant’s expert’s regression-based overcharge estimates since their models had various issues that limited their ability to control for important factors affecting truck prices. This is required to isolate the effects of the cartel.⁶

In Granville, the claimant's expert assumed that a short-term pre-cartel trend would continue indefinitely, ignoring cyclical forces typical for the LCD market. This resulted in a 71% overcharge, which the Court rejected as commercially implausible.⁷

In Stellantis v Autoliv, CAT rejected a model whose high overcharge estimate was inconsistent with potential strong bargaining power of sophisticated buyers.⁸

Most recently, in London Array, both experts’ regression analyses explained very little of the variation in margins despite including many combinations of explanatory variables. The experts agreed that multivariable regression was of relatively low utility in this case, such that the CAT focused on simple margin comparisons alongside other evidence.⁹

German courts echo this sentiment. In the Sugar cartel case, an expert's simulation model was criticized for incorrectly assuming counterfactual prices aligned with perfect competition,¹⁰ ignoring the market's regulatory¹¹ and oligopolistic structure¹². Likewise, a report in the Rail tracks cartel proceedings was deemed useless for using long-term average prices to evaluate cartel effects on individual purchases.¹³ In the Trucks cartel, Berlin and Stuttgart courts criticized expert reports for ignoring Commission findings on the cartel's nature and analysing it as a mere information exchange.^14,15

Will it bend or will it break?

Courts increasingly expect experts to demonstrate that their results are robust to reasonable variations in assumptions, data, and model specification. Judges have criticised analyses that collapse when key parameters are adjusted.

In BritNed v ABB, the claimant's regression-based overcharge evaporated once the analysis was restricted to relevant project. The question Court wanted answered was whether the BritNed submarine project was more expensive, not whether ABB submarine and underground cables were more expensive overall.¹⁶

In Royal Mail v DAF, the CAT expressed disappointment that experts failed to acknowledge "the inherent difficulties in their own approach" or show "recognition of the scope for a range of possible results and of the reasonableness of the other expert's opinion".¹⁷

In the German sugar cartel case, after extensive party criticism of initial models, the court-appointed expert's revised regression analyses proved decisive. The regional court (Landgericht, hereinafter “LG”) Mannheim found the econometric analysis sufficiently robust against modifications the expert deemed appropriate.¹⁸ Multiple specifications yielded overcharge estimates clustered around 2%,¹⁹ and the court ultimately awarded precisely 2% damages,²⁰ aligning with the expert's quantified findings.

Walking the line: Independence in practice

Although formal rules on expert independence differ, UK and German courts are converging on demanding transparency and rigour. In the UK, a party-appointed expert has an explicit duty of independence to the court.²¹ In Germany, experts lack a similar formal duty; their reports are formally considered "substantiated party submissions." However, both jurisdictions have a similar practical expectation: the substance of an expert’s analysis and their functional duty to assist the court take precedence over appointment formalities.

In Royal Mail v DAF, the CAT criticised the defendant's expert for a lack of candour regarding his historic and undisclosed relationship with DAF, emphasising that experts must not only be independent, but be seen to be independent, with full disclosure of matters affecting their objectivity.²² Courts are increasingly critical of experts who cross the line from independent adviser to advocate. This friction was evident in BritNed v ABB, where the court criticised partisan analyses that failed to independently assist.²³

In Germany, the approach is functionally similar, though rooted in different principles. While German experts are not formally independent, their duty to provide complete and truthful evidence under § 138 ZPO is rigorously enforced. In the Rail cartel case, LG Dortmund criticised the defendant's expert reports for failing to incorporate information specifically available to his client and rejected "pure criticism reports" that only attack an opponent's work without offering a constructive alternative.²⁴ In both countries, the practical message is clear: an expert's primary value is providing comprehensive, helpful, and transparent analysis.

Know your audience: Navigating procedural divides

Procedural differences between the UK and German systems are critical for an expert’s effectiveness. The UK’s specialised CAT has developed economic expertise, ensuring higher specialist scrutiny. Nonetheless, the CAT has signalled impatience with excessive complexity. In London Array v Nexans, it criticised the nearly 1,200 pages of expert reports as "excessive," noting only a "small fraction" could be explored at trial. The CAT urged experts to prioritise concise position papers over long reports, emphasising that clarity and accessibility matter as much as rigour.²⁵

Germany’s decentralised system of regional courts means judicial appetite for econometrics varies. Some courts, like LG Mannheim have engaged deeply with complex and technical analysis, while others, like LG Dortmund, are more sceptical of its value. This makes "knowing your court" a key strategic consideration, requiring experts to tailor analysis to a specific court's preferences.²⁶

Conclusion

The rulings indicate that courts are becoming more, not less, demanding in their expectations of economic evidence. In the UK and Germany, the most persuasive economic evidence combines rigour with realism: it explains the market clearly, tests alternative assumptions openly and presents results that withstand scrutiny.