This site uses cookies.

Book Review: 'Proof of Causation in Tort Law (2015)' by Sandy Steel, Cambridge Studies in International and Comparative Law

17/03/17. Assessing causation of injuries and index incident assessment is a complex task as rarely does one event occur in total isolation from other events, trends or predispositions. Lawyers and experts are required to understand and debate theories of injury causation, conduct a qualitative (and sometimes quantitative) analysis of data and attribution, and give a prognosis for future injuries with or without treatment.

The ability to reliably identify a psychological ‘injury’, to understand its causes and to establish appropriate attribution to a trigger event are crucial to the successful functioning of the civil court and to the law firms and the clinical experts who provide services to them(1). Ensuring and maximising evidential reliability involves careful consideration of any pre-injury issues, as well as any pre-event and post-event stressors. This process may well involve ‘apportionment’ i.e. the estimation of the percentage of psychological injury caused as a direct result of the index event, as opposed to other unrelated pre-event or post-event factors. The notion of apportionment is typically applied with respect to three time frames: prior to the index event, the index event period itself and, thirdly, at the time of the medico legal assessment period.

As Steel states at the outset of his fascinating text, causation is a foundation concept in Tort Law. A claimant must demonstrate that the defendant was a cause of the injury suffered in order for compensation to be awarded. He provides in his book a critical, comparative and theoretical analysis of the general proof rules of causation underlying the tort laws of England, Germany and France and the exceptional departures from these rules which each system has made. As such this book is of great interest to law schools, judges, barristers, experts and all legal practitioners and trainees. Steel’s background as Professor of Law at Oxford University and previously at King’s College, London, makes him well placed to provide a cogent review of this important topic.

What concept should apply when there is evidential uncertainty relative to some standard of proof? Issues relating to conceptual problems, problems of consistency and normative problems all need to be addressed, according to Steel.

Firstly, all three national systems refer to the idea of ‘probability’ when considering proof. English Law, for example, requires proof on ‘the balance of probabilities’. The conceptual difficulty is in understanding the extent to which evidence is capable of satisfying legal standards of proof either itself or in combinations with other evidence. Some courts find that statistical evidence on its own is not sufficiently ‘individualised’ or ‘particular’ to the case in hand. Properly taxonomizing different exceptions is important as, according to Steel, we cannot hope to develop the law in a consistent way without understanding the nature of exceptional rules.

Secondly, can exceptional rules be rationally contained without undermining the general rules (5)?

Thirdly, if the general rule(s) can be justified, can existing or further exceptions in the future be tolerated and accepted?

The kinds of casual uncertainty faced by Tort Law consists of general and specific causation, with distinctions between factual and scientific uncertainty by reference to several typical causes of it – namely time (e.g. memories fade; records are lost); multiplicity of possible causes (e.g. two accidents close in time); unobservability of causation (e.g. sustained work stress with no one index event); absence of mechanistic knowledge (e.g. what caused the pervasive depression); counterfactual nature of causation (e.g. the ‘but for’ question) and indeterminism and randomness (e.g. we do not live in a certain or totally predictable world).

This excellent and diligently crafted text is structured to address these complex issues in detail. He concludes with a debate about the relative downside of false positives versus false negatives in the context of civil justice. It is important, in Steel’s view, not to ignore the tangible effects of injustice caused on each/either party by false negatives or false positives. The court should, in his opinion, have regard to the relative abilities of the parties to bear these errors. His concluding sentence is ‘The justificatory burden for departing from the general rules of proof of causation is not easily discharged’.

I found this concise and well-argued text very stimulating and thought provoking and would highly recommend it. I’m sure it will stimulate lawyers and experts to illustrate how these principles and dilemmas apply to practical cases in which they are involved, especially in the field of personal injury and medical negligence – with further modelling to take into account single cause and domino-cause theories, multi-causality theory, with mathematical and non-mathematical analysis to aid the apportionment debate (2).

Dr Hugh Koch
Hugh Koch Associates


  1. Koch HCH & Newns K (2016) Causation of Psychological Injuries and Index Incident Assessment. Expert Witness Journal. Summer 2016.

  2. Koch HCH (2016) Legal Mind: Contemporary Issues in Psychological Injury and Law. Expert Witness Publications. Manchester.

    Image ©