Henry Charles looks at a recent decision from the Court of Appeal which settles the longstanding question of whether material contribution applies to cases of divisible injury.
In this industrial disease claim, the Court of Appeal confirmed inter alia that the doctrine of material contribution applies to divisible and indivisible injury, in doing so shutting the door on nearly a decade’s worth of uncertainty as to whether material contribution applied only to indivisible injuries, or divisible injuries. However, the case sets a number of hares running as to the scope and application of material contribution. There is an old Danish proverb – “prediction is hazardous, especially about the future” but with that in mind we might speculate that ultimately material contribution, never the most popular of concepts, may become rather more circumscribed notwithstanding the new spark of energy Holmes v Poeton provides.
The Facts
C was exposed in the course of his three periods of employment with Poeton to TCE, a carcinogen readily absorbed by the body following inhalation. The TCE was used in a tank for degreasing. It was held that during the first two periods the levels of exposure often exceeded short-term exposure limits, and sometimes exceeded long-term limits. So breach of duty was found. C developed Parkinson’s. Could Parkinson’s be attributed to the exposure?
Material Contribution
It was agreed that Parkinson’s was an indivisible injury in nature. C argued that he could succeed on a material contribution basis. He did not argue that there had been a doubling of risk or for a finding that there had been a material contribution to risk per Fairchild v Glenhaven Funeral Services Limited [2003] AC32 and Barker v Corus UK Ltd [2006] 2 AC 572. Holmes v Poeton is thus firmly in clinical negligence territory from a material contribution perspective.
Stuart-Smith LJ observed that material contribution is:
“an area that has been bedevilled by apparent inconsistency and imprecision at the highest level on multiple occasions. It has, not surprisingly, engendered considerable debate both in the authorities and by contributions from academic scholars, amongst whom Professors Jane Stapleton, Sandy Steel and Sarah Green have been pre-eminent in applying levels of analysis that are frequently absent in the authorities”
The classic definition of material contribution, set out by Professor Sarah Green (Causation in Negligence, Hart Publishing, 2015, Chapter 5, p97), and approved by the Privy Council in Williams v Bermuda Hospitals Board [2016] AC888:
“It is trite negligence law that, where possible, defendants should only be held liable for that part of the claimant’s ultimate damage to which they can be causally linked … It is equally trite that, where a defendant has been found to have caused or contributed to an indivisible injury, she will be held fully liable for it, even though there may well have been other contributing causes …”
In fact, as set out in Holmes v Poeton there has been some substantial friction and the definition might not be quite so trite. Indeed, in Holmes v Poeton it appears that the Court of Appeal thought that the extension to indivisibility had only been enunciated at appellate level relatively recently. For the Court accepted that Bailey v MOD [2009] 1 WLR 1052 (CA) provided the requisite authority that material contribution applied to indivisible injury, albeit without evident enthusiasm. Stuart-Smith LJ at paragraph 63:
“The reasoning in Bailey has been subjected to sustained criticism, not least by Professor Stapleton (Unnecessary Causes, LQR 2013, 39-65 at 50-54). It may well be asked how a principle first enunciated in a case involving a quintessential divisible disease has come to be established as a test that bypasses the need to satisfy the “but for” test in cases of individual injury that do not come within the Fairchild exception. It might, as Professor Stapleton suggests, derive from a response to an evidentiary gap in divisible injury cases where there is no satisfactory acceptable evidentiary basis from which the disability due to the separate insults to the body could be apportioned to the individual sources. But, if so, its transference to the field of indivisible injury or disease has not been explained apart from the recognition that the principle is generous to claimants. I would, however, hold that we are bound in the light of Bailey to find that the Bonnington “material contribution” principle applies to cases of indivisible injury and that, where the principle applies, the claimant does not have to show that the injury would not have happened but for the tortious exposure for which the defendant is responsible.”
Poeton deployed paragraph 130 of AB v Ministry of Defence [2010] EWCA Civ 1317, as defendants have in a number of difficult material contribution cases:
“This principle applies only where the disease or condition is ‘divisible’ so that an increased dose of the harmful agent worsens the disease. As is well known, in Bonnington, the claim succeeded because the tortious exposure to silica dust had materially aggravated (to an unknown degree) the pneumoconiosis which the claimant might well have developed in any event as the result of non-tortious exposure to the same type of dust. The tort did not increase the risk of harm; it increased the actual harm. Similarly in Bailey, the tort (a failure of medical care) increased the claimant’s physical weakness. She would have been quite weak in any event as the result of a condition she had developed naturally. No one could say how great a contribution each had made to the overall weakness save that each was material. It was the overall weakness which led to the claimant’s failure to protect her airway when she vomited with the result that she inhaled her vomit and suffered a cardiac arrest and brain damage. In those cases, the pneumoconiosis and the weakness were divisible conditions.”
The judgment in Holmes v Poet is fairly direct in its observations on AB v MOD. Stuart-Smith LJ at paragraph 65:
“With the utmost respect for the Court of Appeal in that case, I am unable to accept or adopt this analysis. For the reasons I have tried to explain, Bonnington itself was expressed in terms that were appropriate to indivisible rather than divisible diseases and the principle has since been accepted at the highest level on multiple occasions as applying to indivisible diseases; and Bailey was a case directly in point because the injury suffered by the claimant was indivisible.”
Analysis of AB v Ministry of Defence has focussed on the notion that the extract was actually focussed on the issue of proof. As Lord Phillips noted on appeal ((2013] AC 78), there were other potential causes for the injuries sustained by the atomic veterans, there was no basis for a risk doubling analysis and the Fairchild exception did not apply.
There is a general sense with the material contribution cases that no single case ever gets everything quite sorted. Stuart-Smith LJ took aim at Williams v Bermuda Hospitals Board for its obiter observation that in fact Bailey v MOD was a “but for” case.
In any event, Holmes v Poeton seems to settle, for the time being, the question of whether material contribution applies to indivisible injuries. That does avoid the balletic dance of when an injury becomes indivisible.
Material Contribution in Practice in Holmes v Poeton
All of that said, in practical terms material contribution remains complex and often difficult in terms of proof.
As Poeton pointed out, even if it was appropriate to consider a test based on “material contribution”, that did not remove from Mr Holmes the need to prove that the tortious exposure to TCE for which Poeton was responsible was itself a “but for” cause of his Parkinson’s disease. This is where Mr Holmes’ claim foundered. Stuart-Smith LJ at paragraph 112:
“I have summarised the propositions on which the judge based his finding of (individual) causation at [24] above and the main features of the scientific evidence on which he relied. In my judgment, the propositions and evidence on which he relied did no more than to establish that TCE was a risk factor for Parkinson’s disease and that there is a plausible mechanism based on the rodent studies for a finding that TCE may cause or materially contribute to the development of Parkinson’s disease. Although TCE has long been identified as a compound of interest, the evidence to prove generic causation is lacking whether one is applying the legal or a scientific standard of proof. To my mind the critical gap, given the absence of epidemiological evidence supporting a causative link, is the present inability to extrapolate from the rodent studies to the impact of TCE exposure in humans, not least because of the great disparity in relative exposure levels.”
The Court of Appeal did not need to look any further, given the evidence. In clinical negligence claims (and some industrial disease claims) there will often be studies, per Holmes v Poeton, but there will usually be a stronger element of clinical experience to support the literature. The Court of Appeal judgment in Mario Schembri v Ian Marshall [2020] EWCA Civ 358 does show how scientific papers can be used as a scaffold onto which a common sense and pragmatic view of all the evidence can be built to look at where the individual claimant is likely to have fitted. But note that ironically you may be fusing material contribution to risk as an element of proving material contribution to harm in so doing. That may provide some answer to the mildly reformulated test for material contribution reached by Ritchie J (obiter) in CNZ (a minor) v Royal Bath Hospitals NHS Foundation Trust and Another [2023] EWHC 19 (KB):
“where the but for test cannot be satisfied due to scientific gap impossibility then the law will apply the material contribution to the injury test. If the Claimant can prove the breach made a material contribution to the Claimant’s injury which was more than de minimis then damages are to be awarded against the Defendant.”
More Challenges to Come
As hinted at in the introduction, Holmes v Poeton identifies a cornucopia of potential fallback positions. Stuart-Smith LJ at paragraph 120:
“Perhaps as something of a fall-back position, those representing Mr Holmes submitted that there might in some circumstances be a rational or logical way in which responsibility might be allocated even where the injury or disease is of a type that is generally regarded as “indivisible”. We were referred to dicta in Rahman v Arearose Ltd [2001] QB 351 at [19] per Laws LJ, Hatton v Sutherland [2002] ICR 613 at [36]-[42] per Hale LJ, Dickins v O2 plc [2009] IRLR 58 at [45]-[47] per Smith LJ and BAE Systems (Operations) Ltd v Konczak [2018] ICR 1 at [65]-[72] per Underhill LJ. While, in my respectful opinion, those dicta raise questions that might be important (and difficult) in another case, no question of apportioning liability arises in this case since no causative contribution has been shown. For similar reasons, although the prospect was raised by the Court during the hearing, this is not a case which involves oversubscribed causes. These important and difficult questions should therefore be left alone until a case in which they actually arise.”
Rahman v Arearose raises the question of separate damage by way of intervening act as mitigation of causation.
Hatton v Sutherland and Dickins v O2 look at background vulnerability. In Hatton v Sutherland, the then Hale LJ’s Proposition 16 (p. 632F) is:
“The assessment of damages will take account of any pre-existing disorder or vulnerability and of the chance that the claimant would have succumbed to a stress related disorder in any event.”
However, in Dickens v O2 Janet Smith LJ observed, obiter:
“I respectfully wish (obiter) to express my doubts as to the correctness of Hale LJ’s approach to apportionment. My provisional view (given without the benefit of argument) is that, in a case which has had to be decided on the basis that the tort has made a material contribution but it is not scientifically possible to say how much that contribution is (apart from the assessment that it was more than de minimis) and where the injury to which that has lead is indivisible, it will be inappropriate simply to apportion the damages across the board. It may well be appropriate to bear in mind that the Claimant was psychiatrically vulnerable and might have suffered a breakdown at some time in the future even without the tort. There may then be a reduction in some heads of damage for future risks of non-tortious loss. But my provisional view is that there should not be any rule that the judge should apportion the damages across the board merely because one non-tortious cause has been in play”.
BAE Systems (Operations) Ltd v Konczak raises similar issues. Underhill LJ (who of course was one of the judges in Holmes v Poeton) synthesised Rahman v Arearose, Hatton v Sutherland and Dickens v O2 thus at paragraphs 71 to 72:
“71. What is therefore required in any case of this character is that the tribunal should try to identify a rational basis on which the harm suffered can be apportioned between a part caused by the employer’s wrong and a part which is not so caused. I would emphasise, because the distinction is easily overlooked, that the exercise is concerned not with the divisibility of the causative contribution but with the divisibility of the harm. In other words, the question is whether the tribunal can identify, however broadly, a particular part of the suffering which is due to the wrong; not whether it can assess the degree to which the wrong caused the harm.
72. That distinction is easy enough to apply in the case of a straightforward physical injury. A broken leg is “indivisible”: if it was suffered as a result of two torts, each tortfeasor is liable for the whole, and any question of the relative degree of “causative potency” (or culpability) is relevant only to contribution under the 1978 Act. It is less easy in the case of psychiatric harm. The message of Hatton is that such harm may well be divisible.In Rahman the exercise was made easier by the fact (see para. 57 above) that the medical evidence distinguished between different elements in the claimant’s overall condition, and their causes, though even there it must be recognised that the attributions were both partial and approximate. In many, I suspect most, cases the tribunal will not have that degree of assistance. But it does not follow that no apportionment will be possible. It may, for example, be possible to conclude that a pre-existing illness, for which the employer is not responsible, has been materially aggravated by the wrong (in terms of severity of symptoms and/or duration), and to award compensation reflecting the extent of the aggravation.The most difficult type of case is that posited by Smith LJ in her article, and which she indeed treats, rightly or wrongly, as the most typical: that is where “the claimant will have cracked up quite suddenly, tipped over from being under stress into being ill”. On my understanding of Rahman and Hatton, even in that case the tribunal should seek to find a rational basis for distinguishing between a part of the illness which is due to the employer’s wrong and a part which is due to other causes; but whether that is possible will depend on the facts and the evidence. If there is no such basis, then the injury will indeed be, in Hale LJ’s words, “truly indivisible”, and principle requires that the claimant is compensated for the whole of the injury – though, importantly, if (as Smith LJ says will be typically the case) the claimant has a vulnerable personality, a discount may be required in accordance with proposition 16.”
As a practical point, BAE Systems (Operations) Ltd v Konczak is also important in that it sets out the expectations on experts. Irwin LJ stressed that “as a matter of principle, and supporting the fundamental approach that compensation should never become windfall” experts should always (a) consider whether the claimant had a pre-existing diagnosable disorder (b) the level of risk that an injury would have developed as a result of a cause other than the tortious act. In doing so they should bring to bear as much clinical and diagnostic precision as possible.
Ultimately there is probably going to be only a very narrow window for material contribution and the days of it being a get out of jail free card are largely gone (if, in reality, those days ever existed). Paradoxically it may be useful to view material contribution not so much as the get out of jail free card but as a tool for developing “but for” arguments: if, in a difficult case on causation, one focuses on robust proof of material contribution that can be a gateway for either (a) a better understanding of the ensuing divisibility arguments and/or (b) a better foundation for the “but for” case.
Finally, the landscape of material contribution and indeed the wider issues of causation, might become rather interesting if a case (or, more accurately perhaps, a series of cases raising different issues) reaches the Supreme Court. Underhill LJ at paragraph 125 noted reference in Stuart-Smith LJ’s judgment to Professor Stapleton’s criticism of the reasoning in Bailey v MOD. Her analysis of such cases has been accepted in Financial Conduct Authority v Arch Insurance (UK) Ltd [2021] UKSC 1. See paragraph 182-185, which take a broader look at causation. Is causation ripe for a Supreme Court review?
Clinical Negligence Law 