Untangling the threads
A departure from the existing causation test in tortious claims might be required to ensure that a meritorious claim will not fail. Is it a case of ‘no buts, it’s got to be but-for?’, asks Kate Ahern
In tortious claims, the general rule is that the plaintiff must prove, on the balance of probabilities, that the defendant owed the plaintiff a duty of care and that the defendant’s wrongdoing caused the plaintiff’s injury.
The courts usually approach the latter issue by answering the question “Would the injury not have occurred but for the defendant’s actions?”. In other words, would the outcome have eventuated irrespective of the breach?
This test operates efficiently where there is a single cause of the injury. Its limitation is evident in more complicated matters, such as occupational disease where the cause is multifactorial or where there is more than a single tortfeasor.
Difficulties with the traditional test may also arise in clinical negligence litigation, where there may be multiple causes, including pre-existing conditions or where co-morbidities interact.
Position in Ireland
The infant plaintiff in Quinn v Mid Western Health Board suffered catastrophic injuries at birth. The defendants, while acknowledging negligence in care, contended that the injuries were caused by an acute episode in utero requiring early delivery, for which they were not responsible.
Kearns J rejected the proposition of considering an alternative test where the standard test failed: “If I were convinced that defendants who have a substantial connection to the injury were escaping liability because plaintiffs cannot prove causation under currently applied principles, I would not hesitate to adopt [an alternative].
"In my opinion, however, properly applied, the principles relating to causation are adequate to the task. Adoption of either of the proposed alternatives would have the effect of compensating plaintiffs where a substantial connection between the injury and the defendant’s conduct is absent.”
To date, the Irish courts have failed to consider an alternative test. An analysis of our neighbouring jurisdiction might provide a helpful insight into the potential approach to be taken in cases where the ‘but-for’ causation test proves inadequate.
Where a plaintiff may face an injustice on the standard test, the courts of England and Wales have extended the test to that of ‘material contribution’. This concept originated in occupational disease litigation and has since been applied in clinical negligence cases.
Extending the but-for test
This area of law has been described by the English Court of Appeal as involving “complex and difficult questions of law in an area that has been bedevilled by apparent inconsistency and imprecision at the highest level on multiple occasions”.
In that jurisdiction, where the standard test fails, there remains a prospect of recovery for the plaintiff, and the legal principle of material contribution should be considered. Courts can determine whether the defendant’s act materially contributed to the harm – that is, that the cause was more than negligible.
The courts in such cases rely on expert evidence and, if this can show that the defendant’s actions substantially contributed to the harm suffered, then the plaintiff may recover 100% of the damages from that defendant.
Even where the defendant’s negligence was not the sole – or even the most significant – cause, and one or more causes materially contribute to the injury, the claim can succeed.
The courts of England and Wales have dealt with this issue in a number of cases that might provide a useful guide to our courts should the need arise.
In Bonnington Castings v Wardlaw, the plaintiff suffered from pneumoconiosis arising out of silica dust inhalation during the course of his employment with the defendant.
There were two sources of the dust:
- Pneumatic hammers, during which period there was no known protection, and
- Swing grinders – the dust was present owing to a failure to maintain dust extractors on the part of the defendant, rendering it liable.
The expert evidence failed to show which dust was responsible for the disease. In those circumstances, the ‘butfor’ test failed, as the plaintiff was unable to establish that the injury would not have eventuated but for the silica dust exposure.
The court then considered whether the plaintiff had proven that the dust produced by the swing grinders made a substantial contribution to the disease.
The court found that the defendant’s failure contributed dust in levels that were “not negligible to the lungs and were therefore causative”.
Lord Reid continued: “What is the material contribution must be a question of degree. A contribution which comes within the exception de minimis non curat lex is not material, but I think that any contribution which does not fall within that exception must be material.”
The court found in favour of the plaintiff on the basis that the tortious exposure was more than de minimis, therefore it had materially contributed to the illness suffered.
The plaintiff in McGhee v National Coal Board suffered dermatitis from brick kiln dust on his clothing. The defendant did not provide washing facilities, and the plaintiff was forced to wear the dusty work clothing after work until he returned home to wash.
The House of Lords followed Bonnington and found in favour of the plaintiff, holding that the exposure to the brick dust outside of work had contributed to his skin condition and materially increased the likelihood of him developing dermatitis.
In contrast, while the infant plaintiff in Wilsher v Essex Area Health Authority suffered harm at his premature birth, resulting in blindness, and it was accepted that excessive oxygen had been negligently administered to the newborn, the evidence before the court was that numerous other factors could also have caused the harm suffered.
While the defendant’s lack of care was proven, the plaintiff failed to show that it was causative.
The House of Lords allowed the defendant’s appeal, where it was held that there was no satisfactory evidence that excess oxygen is more likely than any of a number of other distinct possible factors to have caused the harm. Inadequate test
In Fairchild v Glenhaven Funeral Services Ltd, the plaintiff developed mesothelioma as a result of exposure to asbestos dust in the course of employment at more than one employer.
Mesothelioma is what’s known as an ‘indivisible disease’ (discussed below), as it may occur following inhalation of a single particle, thereby making it difficult to identify which defendant was responsible for the disease. It also followed that the ‘but-for’ test was inadequate.
The House of Lords held that, in certain special circumstances, the court could modify the ‘but-for’ test to enable causation to be found proved where it is demonstrated that a breach of duty materially increases the risk of the plaintiff contracting an injury.
The court held that it was just to find both defendants liable where their conduct made a material contribution to the outcome.
In Bailey v Ministry of Defence & Anor, the plaintiff suffered a series of incidents culminating in aspirating after vomiting, thereby suffering cardiac arrest and brain damage. The incidents included the non-negligent cause of pancreatitis and the negligent lack of care on the part of the defendant.
The court distinguished this case from Wilsher, in which there had been cumulative causes that resulted in the outcome. The court held that the aspiration was caused by debilitating weakness, which, in turn, was caused by the numerous incidents.
The court modified the but-for test, allowing the plaintiff to succeed, holding that since the contribution of the negligence was more than minimal, causation was established.
CNZ v Royal Bath Hospitals concerned the birth of twins, one of whom suffered profound hypoxic ischaemia, leading to quadriplegic cerebral palsy. The plaintiff contended that the failure to provide a caesarean section in time caused the injury.
The court concluded that, where the but-for test cannot be satisfied due to a lack of conclusive scientific evidence, then the law will apply the material contribution test.
If the plaintiff can prove that the breach made a material contribution to the injury that was more than de minimis, then he should be entitled to recover 100% of the damages.
The recent case of Holmes v Poeton Holdings Ltd also involved occupational disease. The plaintiff claimed that the Parkinson’s Disease he suffered resulted from exposure to unsafe levels of trichloroethylene while at work, forcing his early retirement.
At first instance, the plaintiff was held to have established causation, and the court found the defendant liable for all of the disease.
The defendant appealed on the causation ground, submitting that the trial judge had relied on the wrong legal test where the harm suffered was an ‘indivisible disease’.
Further, the defendant claimed that the court had failed to consider whether the plaintiff would have developed the disease in any event.
The appeal was allowed, as the court found that insufficient evidence had been adduced to substantiate a causative link between the tortious exposure and the disease in circumstances where causation of the disease is multifactorial.
The evidence before the court was that Parkinson’s Disease may result from genetic risk factors and environmental factors.
Divisible v indivisible diseases
The courts have categorised diseases according to divisibility of liability. Lord Justice Stuart-Smith stated in Holmes: “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 she will not be influenced by the total amount of the agent that caused it.”
Diseases resulting from asbestos exposure highlight the distinction between divisible and indivisible diseases. Scientifically, the severity of a case of asbestosis is directly related to the exposure to asbestos.
A defendant may be held liable only for the extent to which they contributed to the injury, therefore the injury is described as ‘divisible’.
Mesothelioma, on the other hand, can eventuate following exposure to a single asbestos fibre.
So where there are a number of defendants, it is medically impossible to say which exposure caused the condition. here it is impossible to divide the damages between defendants, then all are payable by the liable defendant(s).
If the court is unable to make any apportionment between the two or more periods, then the plaintiff will be entitled to recover in full.
In Bonnington, pneumoconiosis is aggravated by every exposure – therefore, it was categorised as a divisible disease. Holmes confirmed that the material contribution principle should also apply to indivisible diseases.
Burden of proof
In the Irish case of Quinn, the plaintiff sought to rely on the Fairchild test in circumstances where there was a question as to the causation of the brain damage.
The plaintiff’s appeal was dismissed, where it was proven that the plaintiff would have suffered the damage regardless of the care provided by the defendant.
At the time of the judgment in Quinn, it was suggested that the use of the Fairchild test required a shift in the onus of proof, obliging the defendant to prove that they did not cause the harm.
In this case, the Supreme Court was reluctant to require a shift in the onus of proof, stating that such would only be done in exceptional circumstances.
Kearns J held that the more relaxed requirements in Fairchild and McGhee should be confined to more exceptional cases. Since then, Holmes has confirmed that no onus shift is appropriate. Accordingly, the Irish courts might be more open to considering the ‘material contribution’ test.
Whether Irish courts follow the English jurisprudence to prevent causing an injustice remains to be seen.
A departure from the existing causation test might be required to ensure that a meritorious claim will not fail owing to the strict nature of the ‘but-for’ test.
Kate Ahern is a practising barrister and former solicitor.
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Kate Ahern
Kate Ahern is a practising barrister and former solicitor