Even the Court of Appeal accepts we've “been bedevilled by apparent inconsistency and imprecision at the highest level on multiple occasions”. Thankfully, we now appear to have at least some clarity.
Summary
The Court of Appeal have recently held in Holmes v Poeton Holdings Ltd [2023] that when it comes to proving causation, personal injury claimants can now rely on material contribution whether their injury is divisible or indivisible.
It's a useful ruling for claimants considering the lower (de minimis) threshold the material contribution test brings. It's not, however, a free pass to proving one’s case. If a claimant struggles to prove causation on ‘but for’ grounds, the material contribution safety net may not be any easier; particularly given it predominantly arises in claims reliant on the boundaries of what medical science can tell us.
It's difficult to understand the implications of this shift without understanding what has changed. So, quite how did we get here?
What is material contribution?
For the purpose of personal injury claims material contribution means an alleged breach has made more than minimal contribution to a given injury. It's most commonly relied on in clinical negligence or industrial disease cases, where issues of medical science are most complex. That complexity, usually arising due to the way injuries (eg cancers) develop and co-morbidities interact, leaves it impossible to prove causation on ‘but for’ grounds in such cases. Thus, the material contribution test was born to ensure meritorious claims did not fail simply because the evidence was complex.
How did we get here?
Bonnington Castings Ltd v Wardlaw [1956] is the natural starting point. In that case the claimant contracted pneumoconiosis during his employment. There were two contributory silica dusts: “guilty” dust from swing grinders and “innocent” dust from pneumatic hammers. The question was whether the “guilty” dust could be a cause of the claimant’s disease. The view reached was that the swing grinders contributed silica dust in levels that were “not negligible to the [claimant’s] lungs” and, therefore, were causative. This was sufficient to establish liability.
This was developed further in McGhee v National Coal Board [1973] which, to avoid the injustice of multiple potential injury causes making ‘but for’ proof an impossibility, allowed causation to be satisfied where the alleged breach has had a material effect on the likelihood of injury. This was eventually followed by Fairchild v Glenhaven Funeral Services [2003], which allowed the ‘but for’ test to be relaxed for claimants who were exposed to asbestos dust working for more than one employer. Fairchild, however, is best thought of as a case of material increase in risk rather than material contribution.
Bailey v MOD [2008] then came along with Waller LJ at paragraph 46 finding that “…where medical science cannot establish the probability that ‘but for’ an act of negligence the injury would not have happened but can establish that the contribution of the negligent cause was more than negligible, the ‘but for’ test is modified and the claimant will succeed.”
Most recently we then had AB v Ministry of Defence [2010] wherein the Court of Appeal held, untouched by the Supreme Court’s involvement in the case, that ‘the Bonnington principle of material contribution applied only to divisible injury’. This left the claimants to prove they would not have suffered from the cancer, an indivisible injury, ‘but for’ the radiation. Ultimately, they were unable to do so and their claim failed.
All then went quiet until cases such as Williams v Bermuda Hospitals Board [2016] started to lay the groundwork for Holmes’ revisiting of Bonnington’s interpretation.
Divisible vs indivisible injury
Now we understand the history of the principle, it is also important to understand the difference between an injury that is divisible and one that is indivisible, particularly given the court’s finding in AB. Paragraph 31 of the Holmes judgment provides us with a good reminder of those definitions, confirming the following:
- Indivisible injury: One that, once contracted, will not have its severity “influenced by the total amount of the agent that caused it.”
- Divisible injury: One which has its severity directly related to the exposure to the agent that caused it.
For example, mesothelioma (a type of cancer associated with asbestos exposure) is indivisible, whereas noise-induced hearing loss is a divisible injury.
What does Holmes change?
The crucial paragraph is 63, in which Stuart-Smith LJ finds that the line of precedent asserting material contribution as a causative test only available in divisible injury cases was wrong. This was, quite simply, because Stuart-Smith LJ considered Bonnington was expressed “in terms that were appropriate to indivisible rather than divisible ones”; an interpretation already alluded to in Williams.
That finding led the court to hold that the correct interpretation of Bonnington means the material contribution test is applicable regardless of injury divisibility, leaving the claimants in Holmes able to rely on it.
What are the consequences?
Routes to liability
From a purely logical perspective, this is a judgment to be welcomed. It does away with the somewhat illogical distinction and better accounts for indivisible injuries, such as cancers or Parkinsons, which may be materially contributed to by tortious conduct but are not all that different in principle to divisible ones, like asbestosis.
As to the impact on claims, it opens up a new route for claimants to seek to prove causation where an indivisible injury is alleged. However, there remains a substantial evidential burden for a claimant to discharge.
Even though the material contribution test provides a safety net if one is unable to satisfy the usual ‘but for’ grounds of causation, if the claimant struggles to prove their case on that usual basis then it follows proving material contribution is also likely to be difficult. In the words of Underhill LJ in Holmes “identification of a plausible mechanism … by itself is not enough [to prove material contribution]”. A claimant will still need to prove that a material contribution was made on the balance of probabilities.
Eyes on the experts
Expert evidence is also set to become all the more important in such claims. Parties will need to ensure it is robust and deals with the merits of any material contribution argument, absent which they may well miss a viable route to proving or defending liability.
This is likely to be a difficult task for experts, given material contribution has historically raised its head in the most scientifically complex matters. Complexity is not, however, something that can be shied away from, but rather something the instructed experts must be asked to confront and explain in a way that assists the parties and the court (ie one they can understand).
It may, for example, be that although a material contribution argument has been raised, scientific knowledge is simply not at a stage where an expert opining reasonably can say that it's more likely than not that the alleged negligence act has in fact materially contributed to an alleged injury.
Contribution claims
What this judgment does not do is change the recoverable damages for a divisible or indivisible injury. It remains the case that where an injury is divisible a defendant may be held liable only for the extent to which they contributed to the injury. Where indivisible, a defendant will be liable for the whole injury, no matter their level of contribution.
As material contribution now applies to the latter, claimants will, in theory, be able to recover the entire value of their alleged injury from a single tortfeasor on material contribution grounds. It is, therefore, suspected that there will be an increase in contribution claims, as those facing a claim as a lone defendant will give real thought to whether there's scope to limit their liability by seeking a contribution from another tortfeasor who has caused (or materially contributed to as the case may be) a claimant’s alleged injuries.
Professional negligence
As with every shift in the law, there is a risk of increased professional negligence claims against personal injury practitioners. These will no doubt be pursued on the basis that:
- Material contribution was not investigated when it should have been
- Had it been, the compensation and/or costs paid would have been different.
To avoid this, practitioners should ensure they remain alert to the change and make reasonable efforts to investigate material contribution. Doing so may even be as simple as ensuring such questions are part of your precedent expert instruction. After all, it is the appointed expert that will provide the evidence a claimant or defendant needs.
Insurers and other claims handlers
Finally, there's the question of what impact this will have on insurers, claims handlers and the decisions they have to make when handling such a claim. Given the importance of expert evidence, which we've already explored, ensuring their opinions are updated in claims to which material contribution can now apply will be key to assessing potential exposure. It will also be crucial to revisit:
- Any offers on liability and quantum which may have been made to check whether they provide adequate protection in the face of a potential further route to liability
- Reserves to ensure they reasonably reflect that same exposure and the potential further cost of the parties investigating something they previously may not have needed to
Quite how these reviews and other consequences materialise in practice will no doubt be something to watch for some time to come.