Causation in negligence - Factual causation: 'but for' test

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Overview

Understanding causation is vital for establishing liability in negligence cases. The 'but for' test acts as a primary method for determining factual causation, a key part of negligence law. This guide reviews the 'but for' test, its history, limitations, and alternatives, providing essential insights for the SQE1 FLK1 exam. By understanding these principles, you'll be prepared to tackle complex causation scenarios and evaluate potential liability in negligence cases.

The 'But For' Test: Principles and Application

The 'but for' test, known as the sine qua non test, is the main method courts use to establish factual causation in negligence cases. It asks: "But for the defendant's breach of duty, would the claimant's harm have occurred?"

To apply the test:

  1. Identify the defendant's alleged breach of duty
  2. Hypothetically remove the breach from the scenario
  3. Assess whether the claimant's harm would still have occurred

The conclusion can be:

  • If the harm would have occurred regardless, there is no factual causation, and thus no liability.
  • If the harm would not have happened without the breach, factual causation is established, possibly leading to liability.

The test relies on the balance of probabilities. The claimant must show it's more likely than not (over 50% probable) that the defendant's breach caused the harm.

Historical Context and Key Cases

The 'but for' test has evolved through case law to address complex situations. Key cases include:

  1. Barnett v Chelsea & Kensington Hospital Management Committee [1969] 1 QB 428

    This case demonstrates strict application. A night watchman died of arsenic poisoning after a doctor failed to examine him. As the doctor couldn't have saved him due to a lack of antidote, the court ruled the negligence didn't satisfy the 'but for' test, and the hospital wasn't liable.

  2. McGhee v National Coal Board [1973] 1 WLR 1

    This case introduced material contribution to risk. The claimant developed dermatitis from brick dust exposure at work. The employer's negligence in providing washing facilities increased risk but didn't directly cause the condition. The House of Lords found increasing risk was enough to establish causation.

  3. Fairchild v Glenhaven Funeral Services Ltd [2002] UKHL 22

    This case expanded the material contribution principle. Multiple employers exposed claimants to asbestos, but it was unclear whose exposure caused mesothelioma. The House of Lords decided that all those who increased risk could be held liable.

These cases illustrate courts' acknowledgment of the 'but for' test's limitations and their readiness to explore alternatives.

Limitations of the 'But For' Test

Despite its value, the 'but for' test has several limitations that can lead to unfair outcomes:

  1. Multiple Sufficient Causes: When multiple causes could independently result in harm, the test may not pinpoint causation for any single cause.

  2. Indeterminate Causation: Sometimes it's impossible to determine which cause led to harm, especially in long-term exposure cases.

  3. Loss of Chance: The test struggles with scenarios where reduced chances, rather than direct causes, are involved.

Alternative Approaches to Causation

To address these limitations, courts have developed alternatives:

  1. Material Contribution to Harm: Courts may recognize causation if negligence materially contributed to harm, even if not the primary cause.

  2. Material Contribution to Risk: In exceptional cases, causation may be found if negligence raised the risk of harm occurring.

  3. Loss of Chance Doctrine: Some areas recognize claims for loss of chance, particularly in medical negligence cases, allowing recovery based on a lost chance of a better outcome.

Advanced Concepts in Causation

Joint and Several Liability

Involving multiple defendants, this principle allows a claimant to recover full damages from any responsible party. The paying defendant can then seek contributions from others.

Example: Two companies discharge chemicals into a river. The claimant can recover all damages from either company, regardless of their share of the pollution.

Novus Actus Interveniens

This "new intervening act" can break the chain of causation if it's:

  1. Unforeseeable
  2. Voluntary
  3. So significant it becomes the main cause of harm

Example: A driver injures a pedestrian. A nurse's unrelated error harms the pedestrian further. The nurse's mistake may break the chain between the driver's negligence and further harm.

Remoteness of Damage

Even with factual causation, damages may not be recovered if harm is too remote. The test asks:

  1. Was the type of harm foreseeable?
  2. Was the extent of harm foreseeable?

The "egg-shell skull" rule means defendants are liable for full harm, even if the claimant's condition worsens the outcome.

Example: A minor accident causes excessive bleeding due to a hidden condition. The defendant is liable for all consequences.

Practical Application: Exam-Relevant Scenarios

  1. The Defective Ladder

    • A painter is injured by a faulty ladder. The 'but for' test establishes causation. The employer is likely liable.
  2. The Multi-Vehicle Collision

    • Driver A's actions cause a crash involving Driver B and C. While Driver A is clearly liable for Driver B's injuries, Driver C's case may require the material contribution principle.
  3. The Toxic Waste Case

    • Two companies pollute a river, harming wildlife. The 'but for' test doesn't apply as pollution would happen with either's waste alone. The material contribution approach could hold both liable.

Conclusion

Understanding the 'but for' test and its complexities is crucial for analyzing causation in negligence cases.