On 1 October 2021, the High Court handed down judgment in the clinical negligence case of Thorley v Sandwell & West Birmingham Hospitals NHS Trust  EWHC 2604 (QB), which dealt with the issue of whether the ‘material contribution’ test, on causation, applies to a case involving ‘indivisible’ disease and a single tortfeasor.
The basic facts of the claim were as follows. The claimant was taking warfarin on a long-term basis for atrial fibrillation. Following up on an acute coronary syndrome diagnosis, the claimant underwent a precautionary coronary angiogram. Due to the associated bleeding risk of this procedure, the claimant was advised to stop taking warfarin 4-days beforehand. Warfarin treatment was restarted 2-days after the procedure, only for the claimant to have an ischaemic stroke, resulting in permanent and severe physical and cognitive disability.
It was argued that the defendant had either caused or ‘materially contributed’ to the occurrence of the stroke by failing to stick to NHS Trust guidelines on warfarin omission. These guidelines stipulated that the untreated period (both pre- and post- angiogram) should have been shorter.
The claimant’s allegation of breach of duty was largely denied (in relation to pre-angiogram warfarin) by the defendant. Mr. Justice Soole found that the defendant was not in breach beyond the extent to which it had admitted (in relation to post-angiogram warfarin).
As such, resolution of the ‘but for’ case on causation was purely ‘academic’. In essence, the judge found that even if the guidelines had been complied with, the claimant would still have suffered his stroke in any event.
However, the alternative case of ‘material contribution’ remained live (to the extent of the admitted breaches).
The question that fell to be determined was whether the ‘material contribution’ modification of the causation test was possible in a case involving an injury that was accepted to be ‘indivisible’.
He set out his conclusions on the law, at paragraphs 147 to 151 of the judgment:
‘On the face of it, the Court of Appeal decision in AB[i] is binding authority that the test of material contribution has no application to a case where (as here) there is indivisible injury and one tortfeasor. However, given the basis on which the appeal in AB was argued and decided, I do not read the decision of the Supreme Court as an implicit endorsement of the proposition.
On the basis of the cited passage, Heneghan[ii] is to the same effect; albeit a later passage might suggest that the distinction between divisible and indivisible injury was being viewed through the lens of the comparative difficulty of proof of material contribution. Thus the Bonnington[iii] test ‘… is to be applied where the court is satisfied on scientific evidence that the exposure for which the defendant is responsible has in fact contributed to the injury. This is readily demonstrated in the case of divisible injuries (such as silicosis and pneumoconiosis) whose severity is proportionate to the amount of exposure to the causative agent’: .
By contrast, the observations of the Privy Council in Williams[iv] provide support for the rival contention; in particular through the endorsement of Professor Green’s statement of ‘trite negligence law’; the treatment of Bonnington as a case where material contribution by a single tortfeasor was established on the basis (at least, as presented to the court) that the injury of pneumoconiosis was indivisible; and the footnote citation of Lord Phillips of Worth Matravers in Sienkiewicz[v]. However whilst evidently highly persuasive, they are not strictly binding even if part of the ratio.
As to the very detailed discussion of the law of material contribution in John[vi] (Picken J), I do not read it as dealing directly with this particular issue.
This is evidently a legal issue which is ripe for authoritative review, at least in a case where it may affect the result. On the basis of strict precedent, I conclude that the reasoning of the Court of Appeal in AB and Heneghan must be followed. Accordingly the claim of material contribution must fail on the basis that this modified test of causation does not apply when there is a single tortfeasor and an indivisible injury’.
Full text judgment can be accessed here.
Providing detailed analysis, Thomas Herbert, of Ropewalk Chambers, concluded that this decision could be seen as ‘rather surprising’.[vii]
He argues that, ‘on the face of it’, Thorley is inconsistent with Bonnington, ‘where there was a single tortfeasor and a single process with two potentially contributory causes (“innocent dust” and “guilty dust”)’.
Indeed, in circumstances where cumulative causes have combined to form a single injury and the precise effect of individual contributions could not be isolated, the ‘material contribution’ approach has been applicable.
Thus, Mr. Herbert suggests that operation of the ‘material contribution’ test may not be as ‘black and white’ as the judgment in Thorley implies:
‘That said, precisely where the line is to be drawn, and the correctness of the many authorities cited, remains a matter for argument’.
It is posited that once the authorities’ differing interpretations and uses of the word ‘indivisible’ are properly understood, it may be possible to reconcile Sienkiewicz and Williams with AB and Heneghan.
[vii] Thomas Herbert, ‘Material Contribution in the Spotlight (Again) following Thorley v Sandwell & West Birmingham Hospitals NHS Trust’ (26 October 2021 Ropewalk Chambers) <https://www.ropewalk.co.uk/knowledge-sharing/blog/clinical-negligence/1853/material-contribution-in-the-spotlight-again-following-thorley-v-sandwell-and-west-birmingham-hospitals-nhs-trust> accessed 6 December 2021.