But-For Scenario Construction Flaw – Detailed Legal Explanation with Case Laws

1. Introduction

A But-For Scenario Construction Flaw arises when a hypothetical alternative situation, used to assess causation, damages, financial losses, or regulatory liability, is incorrectly developed. The “but-for” test asks what would have happened if the alleged wrongful conduct, contractual breach, negligence, or regulatory violation had not occurred.

In banking, competition law, commercial litigation, and financial regulation, but-for scenarios help determine whether a defendant's conduct caused measurable economic harm. An incorrectly constructed scenario may exaggerate losses, underestimate alternative causes, or produce unreliable compensation calculations.

2. Legal Meaning and Concept

A but-for scenario represents the counterfactual position that would probably have existed without the disputed conduct.

For example, if a bank unlawfully refuses financing to a business, the claimant may argue that the business would have earned substantial profits had financing been approved.

However, the calculation becomes legally defective if it ignores market conditions, operational limitations, alternative financing opportunities, or existing business risks.

A reliable but-for scenario must establish:

A legally relevant causal relationship.

Reasonable assumptions supported by evidence.

Appropriate treatment of market and financial conditions.

Separation of losses caused by wrongdoing from unrelated losses.

A defensible method for quantifying damages.

3. Applicable Legal Framework

Under English common law, factual causation frequently involves determining whether the claimant's loss would have occurred without the defendant's wrongful conduct.

The relevant principles include causation, remoteness, mitigation, and the requirement to prove recoverable loss.

In competition law, Article 101 and Article 102 of the Treaty on the Functioning of the European Union address anticompetitive agreements and abuse of dominance. Directive 2014/104/EU establishes rules governing damages actions for competition-law infringements.

In India, Sections 19 and 27 of the Competition Act, 2002 govern competition investigations and remedies, while Section 53N provides for compensation claims.

These frameworks require attention to the relationship between unlawful conduct and the losses claimed.

4. Case Law Analysis

Case 1: Barnett v Chelsea and Kensington Hospital Management Committee [1969] 1 QB 428

Facts: A patient attended a hospital after consuming contaminated tea. Medical assistance was negligently refused, and the patient subsequently died from arsenic poisoning.

Legal Issue: Whether the hospital's negligence caused the patient's death.

Judgment: The court held that the patient would have died even if appropriate medical treatment had been provided.

Legal Principle/Ratio: Factual causation requires establishing that the injury would not have occurred but for the defendant's negligence.

Significance: The decision demonstrates that a counterfactual must consider what would probably have happened without the wrongful conduct.

Case 2: Allied Maples Group Ltd v Simmons & Simmons [1995] 1 WLR 1602

Facts: Solicitors negligently failed to advise a purchaser about contractual protections during a business acquisition.

Legal Issue: How should the court assess losses dependent on hypothetical negotiations involving third parties?

Judgment: The Court of Appeal distinguished between hypothetical actions of the claimant and uncertain actions of third parties.

Legal Principle/Ratio: A claimant generally proves its own hypothetical conduct on the balance of probabilities, while substantial chances involving third-party decisions may be evaluated proportionately.

Significance: The case prevents flawed counterfactual calculations based on treating uncertain commercial outcomes as guaranteed.

Case 3: Sainsbury's Supermarkets Ltd v Visa Europe Services LLC [2020] UKSC 24

Facts: Retailers challenged multilateral interchange fees imposed through payment-card arrangements.

Legal Issue: Whether the arrangements restricted competition and how the appropriate counterfactual affected the legal analysis.

Judgment: The Supreme Court addressed competition restrictions and damages-related issues arising from the interchange-fee arrangements.

Legal Principle/Ratio: Competition assessments must employ legally appropriate counterfactual reasoning rather than unsupported hypothetical market conditions.

Significance: The decision illustrates the importance of realistic market assumptions in competition litigation.

5. Common But-For Scenario Construction Flaws

Frequent defects include unrealistic revenue projections, selective historical data, unsupported assumptions about customer behaviour, incorrect discount rates, and failure to account for independent market developments.

Another important flaw involves assuming that all financial deterioration resulted from the defendant's conduct, even where external economic factors contributed to the loss.

6. Legal Consequences and Corrective Measures

An unreliable counterfactual may result in reduced damages, rejection of expert evidence, unsuccessful compensation claims, or adverse findings concerning causation.

Courts may scrutinise financial forecasts, contemporaneous records, expert methodology, and alternative explanations.

A sound assessment should employ transparent assumptions, credible financial evidence, sensitivity testing, and consistent treatment of uncertainty.

7. Conclusion

But-For Scenario Construction Flaws undermine the reliability of legal causation and economic damages assessments. Courts require counterfactual reasoning grounded in evidence rather than speculation. Proper scenario construction ensures that compensation reflects losses legally attributable to wrongful conduct without creating unjustified financial recovery.