Holmes v Poeton Holdings Limited [2023] EWCA Civ 1377: an overview

Published: 04/12/2023 | News

The Court of Appeal was required to review the development of the law relating to causation of indivisible diseases in and since Bonnington Castings v Wardlaw [1956] 1 AC 613.  Significantly, it held that the Bonnington principle of ‘material contribution’ should apply to indivisible diseases.  However, the Court found that there was insufficient evidence that the Defendant’s tortious exposure of the Claimant to the substance had caused or materially contributed to his disease.  Also, of interest to personal injury, clinical negligence and industrial disease practitioners will be the handling of the causation evidence: for example, determining “generic causation” prior to “individual causation”, reference to the “odds-ratio” and the Bradford-Hill criteria for causality.



The Claimant was employed by the Defendant between 1982 and 2020, and claimed for damages from the Defendant because it acted in breach of its common law and statutory duty in the period from 1982 to 1997 by exposing him to unsafe levels of Trichloroethylene (TCE), an organic solvent, in the course of his employment.  The Claimant was diagnosed with Parkinson’s disease in 2014.  Parkinson’s disease is an indivisible condition.

The Court of Appeal set out at paragraph 31, the definitions of divisible and indivisible diseases:

“It is a characteristic of divisible diseases that, once initiated, their severity will be influenced by the total amount of the agent that has caused the disease.  By contrast, once an indivisible disease is contracted, its severity will not be influenced by the total amount of the agent that caused it.”



As a matter of basic principle, a Claimant is entitled to recover damages for personal injuries caused or materially contributed to by the Defendant’s negligence.  The first issue that the Court of Appeal was required to address was whether: “The judge adopted the wrong test in law for proving causation, namely that it was sufficient in an indivisible injury case to demonstrate a material contribution to injury regardless of whether, but for the tort, the injury would have occurred in any event: “material contribution” and the “but for” test.”

Lord Justice Stuart-Smith stated at paragraph 30 that: “This ground of appeal raises complex and difficulty questions of law in an area that has been bedevilled by apparent inconsistency and imprecision at the highest level on multiple occasions.”

Lord Justice Stuart-Smith comprehensively reviewed the authorities and held at paragraph 60 that: “it seems clear that the Bonnington principle of ‘material contribution’ should apply to indivisible diseases.”  He then set out two facets of a Court’s determination of causation in such cases.

The First, was that of “generic causation”, in this case this was the question “whether exposure to TCE can cause (or materially contribute to the causing of) Parkinson’s disease, the mechanism of interest being the destruction of the patient’s dopaminergic neurons.” (see paragraph 96).  The Court of Appeal held at paragraph 112 that “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.”  It was held that the evidence did not justify a finding of generic causation.

This “generic causation” section of the judgment is of assistance to practitioners in exhibiting some of the methods and considerations in seeking to prove the same:

  1. Legal issues of causation have to be decided on the basis of current knowledge (see Lord Roger Sienkiewicz v Greif (UK) Ltd [2011] 2 AC 229)
  2. Proof of causation for the purposes of legal liability is different from “scientific proof” (see paragraph 94).
  3. The generic causation question should be precisely put, and evidence needed to weigh on that precise question. In this case the fact TCE may have been toxic in other ways was “not informative” (see paragraph 95).
  4. Even though it was found that this was a “material contribution” case, it is of note that at the level of the “generic causation” inquiry, there seemed to be some reliance on the “odds-ratio”/“relative-risk”, which, as determined by one epidemiological study at “1.58” fell “well short of evidencing a causal association” (see paragraph 102). This is an interesting confluence of “but for” and “doubling the risk” type analysis (comprehensively reviewed in Sienkiewicz) in the context of “a material contribution” case.
  5. Also of note was the observation at paragraph 105 that: “neither of the expert epidemiologists thought that application of the Bradford Hill criteria provided an answer. The judge concluded that strict application of the criteria to the facts of the present case “does not really take matters very much further.”” Suggestive, as in Elvicta v Huxley [2000] EWCA Civ 139, that the nine criteria set out by Sir Austin Bradford Hill may offer a helpful aid to assist in analysing the epidemiological evidence on causality.
  6. That whilst rodent studies suggested a “plausible” causal mechanism for TCE causing Parkinsons it was not possible to extrapolate from the same in order to confirm the impact on humans to the legal or scientific standard of proof (see paragraph 112).

The second facet of causation was termed “individual causation”.  Given the negative finding on generic causation it would be necessary for the Claimant, in order to advance his case on this limb, “to show features of his case that are not reflected in the generic evidence that compel a finding of causation, such as a relevant and repeated response to challenge and rechallenge by exposure to TCE”.  This he had been unable to do.  The Court of Appeal held at paragraph 119 that “although it was established that exposure to TCE is a risk factor for the development of Parkinson’s disease, the judge’s finding that tortious exposure to TCE caused or materially contributed to Mr Holmes’ disease was not sustainable on the evidence and wrong.”

Lord Justice Stuart-Smith confirmed at paragraph 63 that following Bailey v MoD [2009] 1 WLR 1052, 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.”

The Court of Appeal, however, found there was insufficient evidence that the defendant’s tortious exposure of the Claimant to TCE had caused or materially contributed to his disease.  Lord Justice Underhill agreed with Lord Justice Stuart-Smith stating at paragraph 123 that: “I do not believe that it was open to the Judge on the evidence before him to conclude that such exposure as the Claimant had experienced to TCE made a material contribution to his developing Parkinson’s disease.”  He went on to confirm that the: “evidence about a possible causative link between TCE exposure and Parkinson’s disease amounts to no more than the identification of a plausible mechanism and that that by itself is not enough.



This is a very important judgment for all personal injury practitioners but particularly those who practise in the industrial disease and clinical negligence domains, where questions of material contribution most commonly arise.

Lord Justice Stuart-Smith’s comprehensive treatment of the case-law, cuts through the assumptions that had been allowed to grow that a divisible injury was required in order for a finding of material contribution to be enough to found liability.  Emphatically, he states that proof of a material contribution defined as “more than de minimis” will be enough to found liability even where the injury is indivisible.  In the authors’ opinion this is welcome: given the number of indivisible conditions with major ramifications, such as cancers and terminal conditions like Parkinsons, that can often be materially contributed to by tortious conduct, there seems really no rationale for treating a material contribution to those conditions any differently to that made to a divisible condition.

Further, Lord Justice Stuart-Smith’s  approach to the matters of “generic” and “individual” causation, defines a neat set of hurdles for practitioners to overcome in order to establish liability in such cases.

Article written by Dr Lindsey Hogg and Stuart Brady whose practices encompass the full range of Chambers’ work, with a particular interest in personal injury and industrial disease claims. For further information, please contact our Clerks.