Learning Outcomes
This article explores the exceptions to the standard 'but for' test for factual causation in negligence, specifically focusing on the 'material increase in risk' principle. For the SQE1 assessment, you need to understand when this principle applies, particularly in cases involving multiple potential causes or scientific uncertainty, and how it differs from the traditional causation test. Your understanding will enable you to identify and apply the relevant legal rules to SQE1-style single best answer questions concerning complex causation scenarios.
SQE1 Syllabus
For SQE1, you must understand the principles of factual causation, including the exceptions to the standard 'but for' test. It is important to recognise situations where proving direct causation is difficult and where the concept of materially increasing the risk of harm might establish liability. As you work through this article, pay particular attention in your revision to:
- the standard 'but for' test for factual causation and its limitations
- the concept of 'material increase in risk' as an exception to the 'but for' test
- key case law establishing and applying the 'material increase in risk' principle (eg McGhee, Fairchild)
- the specific application of these principles in mesothelioma claims and the effect of the Compensation Act 2006
- distinguishing situations where the 'material increase in risk' test applies from those where the standard 'but for' test or the 'material contribution to harm' test is appropriate.
Test Your Knowledge
Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.
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What is the standard test for factual causation in negligence?
- The reasonable foreseeability test.
- The 'but for' test.
- The material increase in risk test.
- The Caparo three-stage test.
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In which case was the 'material increase in risk' principle notably applied where multiple employers exposed the claimant to asbestos, leading to mesothelioma?
- Barnett v Chelsea and Kensington Hospital Management Committee
- Wilsher v Essex Area Health Authority
- Fairchild v Glenhaven Funeral Services Ltd
- Bolam v Friern Hospital Management Committee
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True or false? The 'material increase in risk' test applies only when the claimant can prove, on the balance of probabilities, that the defendant's breach directly caused the harm.
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The Compensation Act 2006 applies specifically to which type of claim involving material increase in risk?
- All industrial disease claims.
- Claims involving multiple tortfeasors.
- Mesothelioma claims caused by asbestos exposure.
- Claims involving clinical negligence.
Introduction
Establishing causation is a critical step in proving negligence. The claimant must demonstrate that the defendant's breach of duty actually caused the damage suffered. The primary test for factual causation is the 'but for' test. However, this test can lead to unjust outcomes in certain complex situations, particularly where there are multiple potential causes of harm or where scientific knowledge is limited, making it impossible to prove exactly which factor caused the injury. In response, the courts have developed exceptions, including the 'material increase in risk' principle. This article examines this exception, its development through key case law, and its application, particularly in the context of industrial disease claims.
Factual Causation: The 'But For' Test and Its Limits
To establish factual causation, the claimant must typically prove, on the balance of probabilities, that 'but for' the defendant's negligent act or omission, the harm would not have occurred (Barnett v Chelsea and Kensington Hospital Management Committee [1969] 1 QB 428). If the harm would have happened anyway, regardless of the defendant's breach, then the breach is not considered a factual cause of the harm.
Problems with the 'But For' Test
The 'but for' test encounters difficulties in scenarios involving multiple potential causes, especially where scientific uncertainty makes it impossible to determine which specific cause led to the harm. For example, if a claimant is exposed to a harmful substance by multiple negligent defendants over different periods, but the resulting disease could have been caused by exposure from any single source, the 'but for' test may fail against each defendant individually. This is because it might be impossible to prove that but for any single defendant's negligence, the claimant would not have suffered the harm.
Another area of difficulty arises with cumulative causes, where multiple factors contribute to the harm. In Bonnington Castings Ltd v Wardlaw [1956] AC 613, the court developed the 'material contribution to harm' test, allowing liability where the defendant's breach materially contributed to the damage, even if it wasn't the sole cause. This differs from the 'material increase in risk' principle, which applies where the breach contributed materially to the risk of damage occurring.
Material Increase in Risk
Where the 'but for' test is inadequate due to multiple potential causes or scientific uncertainty, the courts may apply the 'material increase in risk' test. This exception allows causation to be established if the claimant can prove that the defendant's breach of duty materially increased the risk of the harm occurring.
Key Term: Material increase in risk An exception to the standard 'but for' test for factual causation. It applies where a defendant's breach of duty significantly increased the chance of the claimant suffering a particular injury, even if it cannot be proven that the breach was the direct cause, particularly in cases of scientific uncertainty or multiple exposures to risk factors.
Development of the Principle
The principle originated significantly in McGhee v National Coal Board [1973] 1 WLR 1 (HL).
Worked Example 1.1
Scenario: David worked in a brick kiln for many years. His employer failed to provide showers, meaning he cycled home covered in brick dust daily. He developed dermatitis. Medical evidence could not definitively state whether the dermatitis was caused by the dust exposure during work (non-negligent) or the prolonged exposure due to the lack of washing facilities (negligent), but confirmed the lack of washing facilities materially increased the risk.
Question: Could David establish factual causation against his employer?
Answer: Yes. Applying the principle from McGhee, although David could not prove 'but for' the lack of showers he would not have contracted dermatitis, the employer's negligent failure to provide washing facilities materially increased the risk of him developing the condition. This was sufficient to establish factual causation.
The Fairchild Exception: Mesothelioma Cases
The application of the material increase in risk principle gained prominence in cases involving mesothelioma, a cancer caused by asbestos exposure, often resulting from contact with multiple negligent employers.
Worked Example 1.2
Scenario: A worker was negligently exposed to asbestos dust by Employer A for 5 years and then by Employer B for 10 years. He later developed mesothelioma, which can be caused by a single asbestos fibre. It was scientifically impossible to determine which employer's asbestos exposure caused the disease.
Question: Can the worker succeed in a claim against either Employer A or Employer B?
Answer: Yes, against both. Following Fairchild v Glenhaven Funeral Services Ltd [2003] 1 AC 32 (HL), the House of Lords held that where a claimant suffers mesothelioma due to negligent exposure to asbestos by multiple defendants, but cannot prove which exposure was the specific cause, causation is established against any defendant whose breach materially increased the risk of the claimant contracting the disease. Both employers materially increased the risk.
Exam Warning
The Fairchild exception is specifically tailored to address the evidential difficulties in mesothelioma cases due to the nature of the disease and exposure. It represents a significant departure from the traditional 'but for' test and its application is generally restricted. Do not assume it applies broadly to all cases with multiple potential causes.
Limitations on the Material Increase in Risk Principle
The courts have been cautious about extending the McGhee/Fairchild principle beyond its specific context. In Wilsher v Essex Area Health Authority [1988] AC 1074 (HL), the claimant, a premature baby, suffered blindness. There were five potential causes, only one of which was tortious (excess oxygen administered negligently). The House of Lords refused to apply the material increase in risk principle, distinguishing it from McGhee. It held that where there are several distinct possible causes, the claimant must still prove, on the balance of probabilities, that the defendant's breach was the cause, rather than simply showing it increased the risk. The defendant's negligence was merely one possible cause among others, not a factor that contributed to a single risk agent (like the dust in McGhee).
Subsequent Developments and the Compensation Act 2006
Following Fairchild, the House of Lords revisited the issue of apportionment of damages in Barker v Corus UK Ltd [2006] 2 AC 572 (HL). The court held that liability under the Fairchild exception should be several, not joint and several, meaning each defendant would only be liable for the proportion of risk they created.
This decision caused concern, particularly for claimants where one or more defendants were insolvent. Parliament intervened swiftly by enacting the Compensation Act 2006. Section 3 of this Act specifically reverses the Barker decision only in relation to mesothelioma claims. For such claims, liability is joint and several, reverting to the position established in Fairchild. This means a claimant with mesothelioma can recover full damages from any single negligent employer who materially increased the risk, even if other exposures (including non-negligent ones or periods of self-employment) also contributed to the overall risk.
Revision Tip
Remember the key distinction introduced by the Compensation Act 2006. For mesothelioma claims caused by negligent asbestos exposure, liability is joint and several (Fairchild applies). For other conditions, even if caused by asbestos, or for situations outside the mesothelioma context where the Fairchild exception might be argued, the common law position (potentially including Barker's proportionate liability or the standard 'but for' test) would apply.
Conclusion
While the 'but for' test remains the primary method for establishing factual causation in negligence, the 'material increase in risk' principle serves as a key exception in specific circumstances. Developed through cases like McGhee and significantly applied in Fairchild for mesothelioma claims, it addresses evidential difficulties arising from multiple potential causes or scientific uncertainty. Understanding its scope, limitations (as highlighted in Wilsher), and the specific statutory modification for mesothelioma claims under the Compensation Act 2006 is essential for addressing complex causation issues in negligence for the SQE1 assessment.
Key Point Checklist
This article has covered the following key knowledge points:
- Factual causation requires the claimant to prove the defendant's breach caused the damage, typically using the 'but for' test.
- The 'but for' test can be problematic where there are multiple potential causes or scientific uncertainty.
- The 'material increase in risk' test is an exception, allowing causation if the defendant's breach significantly increased the risk of harm (McGhee).
- This exception was notably applied in Fairchild to mesothelioma cases involving multiple negligent exposures to asbestos.
- The Fairchild exception is generally limited in scope and was distinguished in cases like Wilsher.
- The Compensation Act 2006, s 3, reversed Barker v Corus for mesothelioma claims only, restoring joint and several liability as per Fairchild.
- For mesothelioma claims, liability can be established against any defendant whose breach materially increased the risk, even if other non-negligent exposures occurred.
Key Terms and Concepts
- Material increase in risk
