Introduction
Establishing causation is a fundamental pillar of civil liability claims, with the burden of proof resting on the claimant. However, in medical malpractice cases, determining the precise role of medical error in causing the final injury (such as death, permanent disability, or failure to recover) is often difficult or impossible due to scientific and clinical complexities. In such scenarios, where causation remains uncertain, the traditional civil liability system based on the "all-or-nothing" rule applies. This means that if the claimant cannot prove the causal link to the degree of certainty required by the legal system, they will receive no compensation, even if the physician's fault is established. This approach can lead to unjust outcomes, particularly when marginal differences in the probability of causation result in fundamentally different results (full compensation versus complete deprivation). The difficulties associated with proving causation in medical disputes have prompted scholars and courts in several jurisdictions to reconsider the traditional understanding of causation and damage. Modern tort law increasingly recognizes that scientific uncertainty should not necessarily deprive an injured patient of all compensation when negligent conduct has demonstrably reduced the prospect of a favorable outcome. Consequently, the loss of a chance theory has emerged as an intermediate solution between complete liability and complete exoneration, seeking to reconcile corrective justice with evidentiary limitations. The primary objective of this article is to examine the theoretical and practical challenges of the "loss of a chance" (perte d’une chance) theory as a mechanism to mitigate these injustices in cases of uncertain causation, through a comparative study of the legal systems of selected European countries. By recognizing the "reduction of the chance of recovery or survival" as an independent and compensable damage, this theory seeks to ensure that injured patients receive at least partial compensation. Focusing on medical cases, this article addresses the question of whether this theory can establish a fair balance between the rights of patients and physicians, or whether its challenges outweigh its benefits.
Methods
This research employs a descriptive-analytical method with a focus on comparative study . The scope encompasses European legal systems (including France, Germany, Austria, Spain, Belgium, and England) which have adopted different approaches to this issue. Research data was gathered through the examination of legal texts such as the civil codes of relevant European countries and the Principles of European Tort Law, key judicial precedents (e.g., rulings from the French Cour de Cassation and German case law), and doctrinal views in these jurisdictions. The collected data was then subjected to critical analysis. The aim is to dissect the foundations, implementation, and challenges facing this theory within the context of comparative law.
Results and Discussions
The findings indicate that the loss of a chance theory attempts to circumvent the impasse of proving definitive causal links by redefining the concept of damage from the "final injury" to the "reduction of the chance of recovery or survival." In this model, the lost chance itself becomes an independent and compensable head of damage. The comparative study reveals a dichotomy in approaches across Europe. Countries such as France, Spain, and Belgium have accepted this theory, thereby opening a path to partial compensation. For instance, in French law, compensation is often awarded as a percentage of the final damage, proportionate to the lost chance. In contrast, German and Austrian legal systems, citing the non-recognition of "chance" as an independent, tangible legal right within their civil codes (e.g., §823 of the German Civil Code - BGB), maintain a more cautious stance, largely rejecting the theory and emphasizing the preservation of the traditional rule. The comparative analysis further demonstrates that acceptance of the doctrine reflects a broader evolution in tort law from a strictly factual conception of causation toward a more normative and policy-oriented approach. Rather than focusing exclusively on whether the defendant's conduct can be identified as the definitive cause of the final injury, courts in several jurisdictions have increasingly concentrated on whether the defendant's negligence deprived the claimant of a valuable opportunity for recovery or survival. This shift is particularly significant in medical malpractice litigation, where the progression of disease, pre-existing conditions, and the limits of medical science frequently render causal certainty unattainable. Accordingly, the doctrine seeks to preserve the compensatory function of tort law by recognizing the destruction or reduction of a chance as a legally cognizable injury. Despite its justice-oriented advantage, fundamental challenges limit the theory's efficacy. First, the philosophical challenge of causal determinism targets its core premise. Second, the inherently vague and subjective nature of "chance" creates significant practical problems: a) Ambiguity regarding the objective existence of the initial chance (e.g., in cases of congenital disabilities). b) Lack of objective criteria for calculating the chance percentage and converting it into compensation, leading to arbitrariness in judicial decision-making. c) The problematic distinction between a "reduced" and a "lost" chance. Third, there is a risk of increased frivolous litigation due to the lowered motivational burden of proof and the potential for double recovery. Furthermore, the theory may conflict with the principle of full compensation (restitutio in integrum), as it only covers a portion of the loss. Another significant concern relates to the quantification of damages. The legitimacy of the doctrine largely depends upon the availability of reliable statistical and medical evidence capable of demonstrating the extent to which the defendant's conduct reduced the claimant's prospects. In the absence of transparent and objective criteria, judicial assessments may become excessively discretionary, thereby undermining legal certainty and predictability. Consequently, critics argue that while the doctrine may enhance substantive fairness in individual cases, it risks generating inconsistency and uncertainty at the systemic level. From a policy perspective, concerns are raised about its potential negative impact on professional medical conduct and rising healthcare system costs. Compared to the alternative of "proportional liability based on probabilistic causation," where compensation is directly proportional to the probability that the error caused the harm, the loss of a chance theory suffers from discontinuity and may result in practical injustice in determining compensation amounts.
Conclusion
The loss of a chance theory emerged as a response to the inefficacy of the "all-or-nothing" rule in addressing uncertain causation in medicine and has achieved some success in mitigating unfair outcomes in certain legal systems. However, its theoretical (e.g., the determinism debate) and practical (e.g., subjectivity in assessment) challenges are significant and cannot be overlooked. This theory alone cannot serve as a comprehensive solution. The article's ultimate conclusion is that to achieve sustainable and equitable justice, an intelligent combination of this theory with other mechanisms, such as proportional liability, appears essential. Furthermore, developing transparent legal frameworks that provide more objective criteria for establishing and valuing a "chance," coupled with establishing specialized tribunals for medical disputes, could mitigate its shortcomings. Ultimately, any solution must strike a precise balance between protecting the rights of injured patients and avoiding overburdening the medical profession with liability in a manner that impedes the provision of healthcare services