Justifying Exceptions to Proof of Causation in Tort Law
| DOI | http://doi.org/10.1111/1468-2230.12142 |
| Date | 01 September 2015 |
| Published date | 01 September 2015 |
Justifying Exceptions to Proof of Causation in Tort Law
Sandy Steel*
This article defends a set of exceptions to the general rule in tort law that a claimant must prove
that a particular defendant’s wrongful conduct was a cause of its injury on the balance of
probabilities in order to be entitled to compensatory damages in respect of that injury. The basic
rationale for each exception is that it provides a means of enforcing the defendant’s secondary
moral duty to its victim. The article further demonstrates that the acceptance of this set of
exceptions does not undermine the general rule.
INTRODUCTION
On most moral views, causation matters to individual liability to pay compensa-
tion for another’s injury.1Causation provides both a reason for and a limit to the
imposition of such liability.2On these views, only individuals who bear a causative
relationship to another’s injury should be potentially liable to pay damages to that
person for that injury. These views are plausible, even if open to challenge: there
seems to be strong reason not to make A liable to B if A is not responsible for B’s
injury, and individual responsibility seems to require causation.3
At any rate, the common law of tort reflects this position: the general rule in
tort law is that a claimant must prove on the balance of probability that a
particular defendant’s wrongful conduct was a factual cause of its injury in order
to be entitled to compensatory damages in respect of that injury. As a matter of
substantive law, this requires that but for the defendant’s wrongful conduct the
injury would not have occurred or that the wrongful conduct made a material
contribution to the injury.4As a matter of proof, the claimant must show this on
the balance of probability. This itself comprises two rules: the burden of proof,
which dictates that the claimant loses in the event that proof on the balance of
probabilities is impossible and the standard of proof, which dictates that a fact be
found when it is more probable than not.
*Fellow and Associate Professor of Law, Wadham College, Oxford University. I would like to thank
Jane Stapleton, Nick McBride, Ariel Porat, Sarah Green and the anonymous reviewers for very helpful
comments on an earlier draft. The usual disclaimer applies.
1 S. Kagan, ‘Causation, Liability, and Internalism’ (1986) 15 Philosophy and Public Affairs 41, 41.
2 Not a conclusive reason and not the only limit, of course.
3 For the view that individual outcome responsibility requires causation, see J. Coleman, ‘Doing
Away with Tort Law’ (2008) 41 Loyola of Los Angeles Law Review 1149, 1161–1165. For an
argument that causation is not necessary for individual moral responsibility for an outcome, see C.
Sartorio, ‘Causation and Responsibility’ (2007) 2 Philosophy Compass 749, 758–759.
4 On why ‘material contribution’ does not always collapse into the but-for test, see S. Steel,
‘Causation and Scope of Responsibility’ in K. Oliphant (ed), Law of Tort (London: Lexis Nexis,
2015) at [14.12].
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© 2015 The Author. The Modern Law Review © 2015 The Modern Law Review Limited. (2015) 78(5) MLR 729–758
Published by John Wiley & Sons Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA
Although the general burden of proof rule has been repeatedly affirmed in
English law, exceptions to it have been recognised over the past fifty years.5
These exceptions allow proof that the defendant’s wrongful conduct materially
increased the risk of the claimant’s injury to generate liability in certain contexts,
most notably in cases of mesothelioma caused by exposure to asbestos dust.6In
these contexts, the claimant succeeds despite it being impossible to prove on the
balance of probabilities that the defendant’s wrongful conduct was a but-for
cause of the claimant’s injury or that it made a material contribution to the
claimant’s injury. Such exceptions raise at least three concerns.7First, a moral
concern: what justifies departing from the principle of individual responsibility
reflected in the general rule, so that even proof on a balance of probabilities of
that responsibility is no longer required? Second, a concern of rational limita-
tions. Once proof of causation on the balance of probabilities is no longer
required in one context, the concern is that an exception cannot be consistently
limited to that context and so, if limits are to be found, they must be arbitrary.8
This, in turn, gives rise to a third concern – namely, that the absence of rational
principles leads to uncertainty in the law.
The existing English law on exceptions to proof of causation fails to do justice
to these concerns.9Beyond an appeal to unstructured intuitions of fairness, the
moral concern has not been adequately addressed.10 Nor is it clear how one can
rationally explain the limits of the current exceptions. A claimant is relieved of
proving causation on the balance of probabilities only if causation is impossible to
prove due to uncertainties in scientific knowledge (merely factual impossibility of
proof will not do) and only if the possible causes of the claimant’s injury operate
in a substantially similar way to cause the injury in question.11 The rationality of
these limitations upon the exceptional rules has rightly been doubted.12 Finally, it
is far from clear when causal uncertainty is genuinely due to gaps in ‘scientific’
knowledge or when possible causes should be said to operate in similar ways.
5 For a recent affirmation of it, see Sienkiewicz vGreif (UK) Ltd [2011] UKSC 10 (Sienkiewicz) at [16]
per Lord Phillips: ‘It is a basic principle of the law of tort that the claimant will only have a cause
of action if he can prove, on balance of probabilities, that the defendant’s tortious conduct caused
the damage in respect of which compensation is claimed’.
a detailed overview of the current law, see Steel, ‘Causation and Scope of Responsibility’ n 4
above at [14.20]-[14.27].
7 For all of these concerns in relation to existing exceptions to proof of causation in English law, see
eg, Lord Hoffmann, ‘Fairchild and After’ in A. Burrows, D. Johnston and R. Zimmermann (eds),
Judge and Jurist: Essays in Memory of Lord Rodger (Oxford: OUP, 2013) 69, describing the exception
in mesothelioma cases as ‘an arbitrary rule masquerading as a principled decision, capable of
causing endless difficulties as to the limits of its application’.
8 See J. Morgan, ‘Causation, Politics, and Law: The English – and Scottish – Asbestos Saga’ in R.
Goldberg (ed), Perspectives on Causation (Oxford: Hart, 2011) 62–63.
9 For a more detailed vindication of these claims, see S. Steel, ‘Causation in English Tort Law: Still
Wrong After All These Years’ (2012) 31 University of Queensland Law Journal 243, 246–259.
10 See, again, Morgan, n 8 above, 61: ‘[Fairchild] does little to identify or justify the making of an
exception’.
above at [22] per Lord Bingham; and at [170] per Lord Rodger.
12 See, eg, R. Stevens, Torts and Rights (Oxford: OUP, 2007) 51; A. Beever, Rediscovering the Law of
Negligence (Oxford: Hart, 2007) 484. See also, below, 746.
Causation
© 2015 The Author. The Modern Law Review © 2015 The Modern Law Review Limited.
730 (2015) 78(5) MLR 729–758
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