3.1.2 Causation Lecture

The conduct of the defendant must cause the damage that the claimant has suffered.

Factual Causation

Tort uses a ‘but for’ test in order to establish a factual link between the conduct of the defendant and the injuries caused: ‘but for the defendant’s actions, would the harm have occurred?’ If yes, causation cannot be shown, and visa-versa.

Matters of causation are decided on the balance of probabilities, and the burden of proof rests with the claimant. Thus, if a defendant is found to be 55% likely to have caused the claimant’s harm, they will be held entirely responsible for the harm; the all or nothing approach.

Specific Rules of Factual Causation

Multiple causes of harm can be:

  • Concurrent (causes which occur at the same time). The general rule here is that the claimant will not have to show that a defendant’s actions were the sole cause of the injury suffered, but just that the defendant’s actions materially contributed to the harm (Bonnington Castings Ltd v Wardlaw [1956]).

    Where the claimant can show nonetheless that their employer has contributed materially to the risk of an injury occurring, liability may still arise where causation cannot be established under the general rule (McGhee v National Coal Board [1973]; Fairchild v Glenhaven Funeral Services [2002]). This may be the case even where an employee is partially to blame for their own exposure (Barker v Saint Gobain Pipelines [2004]). Liability is now generally proportional (Barker v Corus), except where the case involves mesothelioma, in which joint and several liability remains (s3 Compensation Act 2006).
  • Successive (causes which take place one after the other). In such cases, the earlier cause is deemed to be responsible (Performance Cars Ltd v Abraham [1962]).

Lost Chance Cases

Courts are generally unlikely to compensate a claimant for the loss of a chance, where the lost chance is less than 50% (Hotson v East Berkshire Area Health Authority [1987]), because the defendant must have caused the harm according to the balance of probabilities. This approach can seem unfair on patients who lose significant, but not quite significant enough, chances of recovery or similar. However, it is beneficial for claimants who can establish liability, as they can recover full (and not proportional) damages for the harm.

Vindication of Rights Cases

Conventional causation and the all or nothing approach may be disregarded in a slim category of cases in which policy considerations warrant a different approach. For example, in Chester v Ashfar [2004], a claimant who underwent an operation with a 1-2% risk, and for whom the risk subsequently materialised, was able to establish liability because the doctor had failed to warn her of the risk. Though she could not show that she would have declined the operation had she known, the courts acknowledged that the doctor had done wrong and the patient had been unable to properly consent.


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