Is material contribution restricted to divisible injuries?

I wrote an article in June last year on material contribution after the case of Davies v Frimley Health NHSFT 2021 EWHC 169 QB. Since then another first instance judge has again expressed obiter remarks on the topic in the case of Thorley v Sandwell and West Birmingham NHS Trust 2021 EWHC 2604 QB.

Like Davies, the judge in Thorley also expressed the view that material contribution only applies to divisible (in the sense of dose related) injuries. This article addresses whether that principle is correct and considers the leading authorities on the point – MOD v AB and Others 2010 EWCA Civ 1317 and Williams v Bermuda 2016 UKPC 4.


As a former medic, even after 25 years at the Bar, I am still surprised sometimes at how lawyers can take a fundamentally fairly simple principle and over many years complicate it so that it becomes almost unrecognisable and unintelligible.

A little like my favourite topic – Bolam and other tests for breach of duty – this area of law is littered with over-elaborate and inconsistent terminology. The two key terms here are –

Divisible injury –

  • one that is dose related;
  • the longer the exposure or the extent of the causative agent, the greater the injury;
  • for example smoking causing bronchitis – the more you smoke the worse the bronchitis.

Indivisible injury –

  • the opposite of divisible;
  • not dose related to the cause;
  • an injury which is “on/off” – you either have it or you don’t;
  • for example smoking causing lung cancer.

By the way, am I the only one who thinks “divisible” actually means “capable of being divided”, not “dose related” ?

And in a causation sense means that you can apportion different proportions of the overall injury to different causes ?

If so, this again illustrates the inconsistency and lack of logic to terminology used in material contribution cases. If you can apportion a proportion of the injury to the negligent cause, then the Claimant only recovers for that part and material contribution does not apply as a test for causation – see para 134 of MOD v AB.

For the purpose of clarity therefore, I will use the term “divisible (dose related) injury”, and I suggest you do too.

The case FOR the assertion that material contribution only applies to divisible (dose related) injuries

MOD v AB and Others 2010 EWCA Civ 1317

The source of this assertion is the Court of Appeal decision in MoD v AB

You may recall that this was a limitation case involving atomic veterans; the Court was looking at the issue of causation in considering the strength of the Claimant’s case because this in turn was relevant to whether the Court should exercise its discretion under section 33.

Summarising the Defendant’s submission and referring to the material contribution test set out in Bonnington Castings v Wardlaw 1956 AC 613, Lady Justice Smith stated at para 134 –  

“This method of proving causation (by showing that the tort made a material contribution to the condition or disease) is only available where the severity of the disease is related to the amount of exposure; further exposure to the noxious substance in question is capable of making the condition worse.” 

Later at para 150, Lady Justice Smith states –

“We accept that, at least so far as cancers are concerned, the claimants cannot rely on proving that the radiation exposure has made a material contribution to the disease, as in Bailey and Bonnington CastingsThis principle applies only where the disease or condition is ‘divisible’ so that an increased dose of the harmful agent worsens the disease”.

However there are two earlier cases in which Lady Justice Smith seems to have expressed the opposite view.

In Bailey v MoD 2008 EWCA Civ 883 she was part of the Court of Appeal in, perhaps, the most definitive case on material contribution, in which the Court of Appeal set out the circumstances in which it applied and what the test was. The injury in Bailey was cardiac arrest and brain injury – so Lady Justice Smith and the Court of Appeal in that key case applied material contribution to what seems to be clearly an indivisible (not dose related) injury.

In addition, Lady Justice Smith expressly considered that material contribution applied to indivisible (not dose related) injuries in Dickins v O2 plc 2008 EWCA Civ 1144. She states at para 42, having quoted the material contribution test in Bailey,  and questioning why material contribution did not apply to the current case (psychiatric injury caused in part by tortious stress at work) –

“My immediate reaction to the question of apportionment in the instant appeal was to wonder whether this case was any different from Bailey. Was this not a case of an indivisible injury (the respondent’s seriously damaged state following her breakdown) with more than one cause. It was not possible to say that, but for the tort, the respondent would probably not have suffered the breakdown but it was possible to say that the tort had made a material contribution to it. If that is correct analysis, should not the starting point have been that the respondent was entitled to recover in full ?

Furthermore, it seems significant to me that the Court of Appeal in MoD v AB were dealing with a personal injury claim (not a clinical negligence one which is where material contribution so often seems to be relevant to causation) and also that they expressly stated their judgment on the issue as being qualified – “at least so far as cancers are concerned”, rather than of general application.

The case AGAINST the assertion that material contribution only applies to divisible (dose related) injuries

Williams v Bermuda 2016 UKPC 4  (Privy Council)

This was the later case where a delay in treating appendicitis resulting in sepsis was claimed to have caused injury to the Claimant’s heart and lungs. It eventually found its way via the Court of Appeal to the Privy Council (being a case from Bermuda).

Both the cases of MoD v AB and Bonnington were relied by the Defendant in this case – as part of their argument that material contribution could not be used by the Claimant (MoD v AB is not referred to in the judgment but was relied on and is listed as having been cited in the ICLR report of the case).

Giving judgment, Lord Toulson stated at para 31 –

“As Professor Sarah Green has succinctly observed (Causation in Negligence, Hart Publishing, 2015, Chapter 5, p 97):

            ‘It is trite law that, where possible, defendants should only be held liable for that part of the claimant’s ultimate damage to which they can causally be 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 Bonnington there was no suggestion that the pneumoconiosis was ‘divisible’, meaning that the severity of the disease depended on the quantity of dust inhaled.”

This appears to suggest that the principle relied on, that in Bonnington the injury was regarded as a divisible (dose related) injury and that material contribution is therefore limited to such injuries, is not correct.

And there is a footnote –

“In later cases it has been the accepted view that pneumoconiosis is a ‘divisible’ disease, its severity being dependent on the quantity of dust inhaled; and, therefore, where there has been more than one source of toxic material, the extent of the liability of a defendant responsible for part of the exposure should reflect the degree of injury suffered by the Claimant as a result of that exposure. See the judgment of Lord Phillips of Worth Matravers in Sienkiewicz v Grief (UK) Ltd 2011 2 AC 229, para 90: ‘Where the disease is indivisible, such as lung cancer, a defendant who has tortiously contributed to the cause of the disease will be liable in full. Where the disease is divisible, such as asbestosis, the tortfeasor will be liable in respect of the share of the disease for which he is responsible’.”

This Privy Council judgment therefore in my view provides strong support for material contribution not being limited to divisible (dose related) injuries.


My interpretation of the case law over the last 60 years is that it overwhelmingly supports material contribution not being limited to divisible (dose related) injuries in clinical negligence cases, that there is no such restriction and that, once the “But for” test does not apply (see Bailey), material contribution is of general application.

That view is supported by my experience at trial; I won a contested material contribution argument shortly after Bailey.

It is also of note that the two most important cases on material contribution – Bailey and Williams – did not themselves involve obviously dose related injuries – cardiac arrest and brain injury in Bailey and heart and lung injury in Williams. If there was such an important limitation in application of the principle, you might it expect it to have featured in these two important cases.

It may be that one of these first instance cases will be appealed and the principles clarified. It is certainly an area of law crying out for clarification, rather than more confusion.

Finally a plea. Material contribution is an important test for causation in clinical negligence cases. It has historically been underused due to the confusion which has grown up around it. It is time to demystify it as a principle, be clear in the terminology we use and argue it where appropriate with confidence.