Why material contribution applies both to divisible and indivisible injuries

Written by: John de Bono KC
Published: 25 November 2023

  1. If you ever worry that you find it hard to get your head around material contribution then stop. You are not alone.
  1. The Court of Appeal has now given welcome clarification and explained:
    1. That material contribution causation applies both to divisible and indivisible injuries.
    2. That this area of law “has been bedevilled by apparent inconsistency and imprecision at the highest level on multiple occasions.” [in other words it wasn’t just you and you weren’t imagining it].

  1. In a brutally effective summary of the authorities Stuart-Smith LJ in Holmes v Poeton Holdings [2023] EWCA Civ 1377 explains why it is nonsense to suggest that material contribution cannot apply in principle to indivisible injuries just as much as divisible ones.
  1. The Claimant in Holmes developed Parkinson’s Disease and at first instance this was found to have been materially contributed to by his negligent exposure to chemicals at work. The Defendant appealed arguing that Parkinson’s was an indivisible disease to which material contribution did not apply.  The Court of Appeal held that material contribution applies to both divisible and indivisible injuries.  Mr Holmes still lost though, the Court of Appeal finding that there was not enough evidence that his chemical exposure had materially contributed to his Parkinson’s, only that it might have done.
  1. Stuart-Smith LJ starts with a neat definition and example of what is meant by divisible and indivisible injuries, and acknowledges that there has been considerable judicial confusion on this issue:

“First, the terms “divisible” and “indivisible” disease or injury are ubiquitous. They are (or should be) now well understood but have been a source of confusion in the authorities. 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. The classic distinction in asbestos-related diseases is between asbestosis and mesothelioma. Mesothelioma is an indivisible disease because, although the risk of developing a mesothelioma increases in proportion to the quantity of asbestos dust and fibres inhaled, the condition once caused is not aggravated by further exposure and the severity of the condition, if it occurs, is not thought to be affected by variations in the victim’s overall exposure. Asbestosis is a divisible disease because all of the victim’s exposure to asbestos will contribute to the severity of his eventual disease: see Fairchild at [6] per Lord Bingham of Cornhill.”

  1. Noise-induced hearing loss and pneumoconiosis are divisible diseases and this is what has given rise to confusion. If we go back to the beginning and Bonnington Castings v Wardlaw,  non-guilty dust from hammers and guilty dust from swingers materially contributed to the outcome and the claimant recovered 100%.
  1. Because pneumoconiosis was a divisible disease some thought, “Ah, material contribution only applies to divisible diseases”. The Court of Appeal in  AB v MoD made this mistake and suggested that Bonnington (pneumoconiosis) and Bailey (weakness, leading to an airway blockage and death) were cases of divisible injury.  Stuart-Smith LJ is unequivocal in his rejection of this error by the Court of Appeal in AB:

“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.”

  1. The key point made by Stuart Smith LJ is that even though Bonnington was dealing with a case of pneumoconiosis, a divisible disease, the House of Lords treated it as though it was an indivisible disease. After that everything falls into place and material contribution applies to both divisible and indivisible injuries.
  1. The (obiter) treatment of causation in Thorley can now formally be consigned to the archive and need never be referred to again. Troubled by the distinction between divisible/ indivisible injuries, Soole J suggested an authoritative review was required but thought he was bound by AB v MoD.
  1. Going forward, clinical negligence practitioners can concentrate on the real issue in material contribution: i.e. a) would the outcome probably have been the same in any event and b) has the breach of duty more than negligibly contributed to the outcome, without being distracted by the side-issue of whether or not the injury is divisible or indivisible.