Material contribution to harm CASES

In English tort law, material contribution to harm is a route to proving causation where several factors combine to produce a single, indivisible injury. Instead of asking whether the defendant’s breach was the sole or “but for” cause, the court asks whether it made a material (more than minimal) contribution to the harm that actually occurred. This is different from material increase in risk, which (on narrow facts, notably mesothelioma) treats an increased risk as sufficient even where the causal mechanism cannot be disentangled.

Definition and principles

The doctrine applies where (i) the claimant suffered a single injury or disease; (ii) multiple causal factors operated cumulatively; and (iii) the defendant’s breach made a more-than-trivial contribution to that injury. If those elements are met, factual causation is established. The court then addresses scope of duty, remoteness, and quantum in the usual way.

Where it is used

• Industrial disease and exposure cases: successive or concurrent exposures (dust, noise, chemicals) combine to cause a single condition; each negligent contributor is liable, with contribution between defendants.
• Clinical negligence: negligent delays or sub-standard treatment that cumulatively weaken the claimant and lead to an indivisible injury (for example, sepsis or brain damage). Each negligent episode that materially contributed can satisfy causation.
• Accidents with multiple mechanisms: two negligent acts operate together (e.g., collision plus negligent post-incident handling) to produce a single injury.

What it is not

It is not a licence to recover for a mere risk of harm. Where science cannot say which of several exposures caused an injury and the law exceptionally accepts increased risk as sufficient, that is the material increase in risk exception (narrow, principally mesothelioma). Keep the two doctrines distinct.

Divisible and indivisible harm

For indivisible injuries (e.g., a stroke), defendants who materially contributed are each liable for the whole, subject to contribution between them. For divisible harm (e.g., cumulative hearing loss), the court may apportion liability by causal share.

Evidence and experts

Prove the mechanism by which factors combined: timelines, occupational or clinical records, exposure data, and reasoned expert opinion (medical, epidemiological, engineering). Experts should explain why the defendant’s breach made a real (more than de minimis) difference to the injury, not merely to risk.

Practical importance

For claimants, frame the injury as cumulative and indivisible where appropriate, and pinpoint the defendant’s concrete contribution. For defendants, test whether the injury is truly indivisible, whether non-negligent factors dominate, and whether the evidence shows contribution to harm rather than risk.

See also: Causation; But-for test; Material increase in risk; Chain of causation; Scope of duty; Remoteness; Contribution between tortfeasors.