Causation in negligence - Apportionment of liability between...

Learning Outcomes

This article explains how English law apportions liability between multiple tortfeasors in negligence, including:

• Joint and several liability for indivisible injuries, its effect on claimants’ recovery options, and how defendants recoup contributions from one another
• The operation of the Civil Liability (Contribution) Act 1978, including the “same damage” requirement, just and equitable apportionment, and limitation under the Limitation Act 1980, s10
• How to distinguish divisible from indivisible injuries in exam scenarios, and the consequences of that classification for damages and liability
• When courts rely on material contribution to damage rather than a strict “but for” analysis, especially in cumulative exposure and industrial disease cases
• The limited role of material increase in risk, focusing on Fairchild and Sienkiewicz, and why it is confined largely to mesothelioma claims
• The effect of the Compensation Act 2006, s3 on mesothelioma claims, making each responsible tortfeasor liable in full with contribution dealt with separately
• Key factors guiding apportionment between defendants, such as blameworthiness, causative potency, duration and intensity of exposure, and contributory negligence
• How novus actus interveniens interacts with multiple causes, and when an intervening act will or will not break the chain of causation
• Typical SQE1-style problem questions involving multiple defendants, successive employers, and mixed causal mechanisms, and how to structure concise, marks-focused answers

SQE1 Syllabus

For SQE1, you are required to understand how liability is divided between multiple defendants in negligence claims, with a focus on the following syllabus points:

• the meaning and effect of joint and several liability in negligence
• how courts apportion damages between tortfeasors under the Civil Liability (Contribution) Act 1978
• the application of the material contribution and material increase in risk doctrines
• the distinction between divisible and indivisible injuries
• how these principles are applied in multi-defendant and multi-cause scenarios
• how the Compensation Act 2006, s3 affects mesothelioma claims when exposure occurred with multiple employers
• practical features of contribution claims, including “just and equitable” apportionment and the Limitation Act 1980, s10 (time limits for contribution claims following judgment or settlement)

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.

1. What is the effect of joint and several liability in a negligence claim involving multiple tortfeasors?
2. How does the Civil Liability (Contribution) Act 1978 allow courts to apportion damages between defendants?
3. When is the doctrine of material contribution to damage applied, and what does it mean for liability?
4. In what circumstances will a court apply the principle of material increase in risk?

Introduction

When more than one defendant is responsible for a claimant’s injury or loss in negligence, the law must decide how liability and damages are divided. This article explains the key principles for apportioning liability between tortfeasors, including joint and several liability, statutory contribution, and the doctrines of material contribution and material increase in risk. These rules ensure claimants are compensated while distributing financial responsibility fairly among defendants.

Understanding whether an injury is divisible or indivisible is the starting point. Indivisible injuries (such as a single fracture or a discrete psychiatric illness from one incident) typically engage joint and several liability across all tortfeasors responsible for the same damage. Divisible injuries (for example, cumulative hearing loss or progressive lung disease where the harm is capable of being split among different periods or exposures) permit proportionate damages against each tortfeasor based on their contribution to the whole injury.

Where scientific uncertainty prevents proof of “but for” causation across multiple exposures, two causation doctrines are central. Material contribution (as used in industrial disease where cumulative exposures cause a single disease) permits liability where the defendant’s breach made a more than minimal contribution to the damage. Material increase in risk (limited to special categories such as mesothelioma) can permit liability where exposure has significantly increased the risk of contracting the disease but the precise causal exposure cannot be proved. In mesothelioma, Parliament has confirmed by the Compensation Act 2006, s3 that each responsible exposure renders the tortfeasor liable for the whole damage to the claimant, with contribution between them determined later.

Joint and Several Liability

Where two or more defendants have each contributed to a single, indivisible injury, English law imposes joint and several liability. This means the claimant can recover the full amount of damages from any one of the defendants, regardless of their individual share of fault.

Key Term: joint and several liability
Where more than one defendant is liable for the same damage, the claimant may recover the full amount from any one defendant. Defendants are then left to sort out financial responsibility between themselves.

This rule protects claimants from the risk that one defendant is insolvent or untraceable. It also encourages defendants to seek contribution from each other, rather than leaving the claimant under-compensated. For indivisible injury, both “blameworthiness” and “causative potency” of each defendant’s conduct will matter when they later pursue contribution against each other. Importantly, the claimant’s total recovery is limited to one full compensation; there is no double recovery.

Worked Example 1.1

Two drivers, A and B, are both negligent and cause a collision that injures a pedestrian, C. C suffers a single broken leg. C sues both A and B and is awarded £20,000 in damages. A is uninsured and cannot pay.

Answer:
C can recover the full £20,000 from B. B can then seek a contribution from A for A’s share of responsibility, but C is not affected if A cannot pay.

Statutory Contribution Between Tortfeasors

The Civil Liability (Contribution) Act 1978 allows a defendant who has paid more than their fair share of damages to recover a contribution from other liable defendants. The court decides the amount of contribution based on what is just and equitable, considering each party’s responsibility for the damage.

Key Term: contribution
The right of a defendant who has paid damages to recover a fair share from other defendants who are also liable for the same damage.

The Act applies to all torts, including negligence, and covers both joint and several liability situations. Contribution can be pursued in the same proceedings via a Part 20 claim or in later proceedings. The Limitation Act 1980, s10 imposes a two‑year period from the date a person seeking contribution is held liable by judgment or has paid under a settlement to start the contribution claim. When apportioning, courts commonly assess both culpability and the causal contribution of each tortfeasor.

Worked Example 1.2

C is injured in a car accident caused by the negligence of both D1 (70% at fault) and D2 (30% at fault). C recovers £100,000 from D1 alone.

Answer:
D1 can claim £30,000 from D2 under the Act, so that each pays a share reflecting their responsibility.

Divisible and Indivisible Injuries

The way liability is apportioned depends on whether the injury is divisible (can be split between causes) or indivisible (cannot be separated).

• For indivisible injuries (e.g., a single broken bone), all defendants are jointly and severally liable for the whole loss.
• For divisible injuries (e.g., hearing loss caused by exposure to noise at different jobs), each defendant is liable only for the harm they caused.

Key Term: divisible injury
An injury that can be separated into parts, each attributable to a different cause or defendant.

Key Term: indivisible injury
An injury that cannot be separated into parts; all defendants are liable for the whole.

In practice, courts look for evidence enabling them to identify and quantify the part of the cumulative harm caused during particular periods or by particular defendants. Where evidence allows, proportionate damages follow for a divisible injury (for example, progressive asbestosis or noise-induced hearing loss), often based on duration and intensity of exposure.

Worked Example 1.3

E works for two employers, F and G, both of whom negligently expose E to silica dust. E develops a lung disease. It is impossible to say which exposure caused the disease, but both exposures materially contributed.

Answer:
Both F and G are jointly and severally liable for E’s disease. E can recover full damages from either, and F and G can seek contribution from each other.

Worked Example 1.4

Hearing loss accumulates over years. X worked for three employers: J (5 years high noise), K (3 years medium noise), and L (2 years low noise). Each failed to protect X and contributed to X’s audiometric deficit.

Answer:
Hearing loss is a divisible injury. Each employer is liable only for the portion of loss caused while X worked for them. The court will apportion damages just and equitably, commonly using duration and intensity of exposure (e.g., J bears a larger share than K, which bears more than L).

Material Contribution to Damage

When a claimant’s injury is caused by multiple factors, and it is impossible to say which factor caused what proportion of the harm, the court may apply the material contribution doctrine. If a defendant’s breach of duty made a material (i.e., more than minimal) contribution to the overall injury, that defendant is liable for the whole injury.

Key Term: material contribution
Where a defendant’s breach of duty made a more than minimal contribution to the claimant’s injury, they are liable for the whole injury, even if other factors also contributed.

This doctrine is especially important in industrial disease cases, such as those involving exposure to harmful dust or chemicals from multiple sources, where cumulative exposures together cause a single condition. It functions as an evidential solution when the ordinary “but for” analysis cannot be applied to allocate precise proportions for an indivisible injury caused by concurrent exposures.

Worked Example 1.5

M is negligently exposed to “guilty” respirable dust at a foundry that should have been extracted, while other dust is unavoidable (“innocent”). The cumulative exposures cause pneumoconiosis, but the medical evidence cannot separate their shares.

Answer:
Because the negligent exposure materially contributed to M’s disease, the foundry is liable for the whole injury. If there are multiple negligent sources materially contributing, each is jointly and severally liable, with contribution between them determined on a just and equitable basis.

Material Increase in Risk

In some cases, especially where scientific uncertainty makes it impossible to prove which exposure caused the harm (such as mesothelioma from asbestos), the court may impose liability if the defendant’s breach of duty materially increased the risk of the claimant suffering the injury.

Key Term: material increase in risk
Where a defendant’s breach of duty significantly increased the risk of the claimant suffering harm, and it is impossible to prove which exposure caused the injury, the defendant may be liable.

This principle (from the Fairchild line of cases and affirmed in Sienkiewicz v Greif) is strictly limited to special categories characterized by scientific uncertainty. In mesothelioma, Parliament intervened with the Compensation Act 2006, s3: where a person has negligently (or in breach of duty) exposed the claimant to asbestos and the claimant contracts mesothelioma, each responsible person is liable for the whole of the damage. Apportionment then occurs between defendants by contribution; the claimant’s recovery is not reduced because exposure cannot be allocated.

Worked Example 1.6

H worked for three employers, each of whom negligently exposed H to asbestos. H develops mesothelioma, but it is impossible to prove which exposure caused the disease.

Answer:
Each employer is jointly and severally liable for H’s loss, as each materially increased the risk of H developing mesothelioma. Under Compensation Act 2006, s3, H can recover the whole from any one employer, who may then seek contribution from the others.

Worked Example 1.7

N is diagnosed with mesothelioma after exposures with two shipyard employers. Medical science cannot determine which exposure initiated the malignancy.

Answer:
Each employer’s negligent exposure materially increased N’s risk of mesothelioma. N may recover full damages from either. The paying employer may then recover a contribution from the other in a proportion the court finds just and equitable.

Apportionment and Contribution in Practice

When a claimant recovers full damages from one defendant, that defendant can seek a contribution from others. The court will apportion liability based on each defendant’s share of responsibility for the damage, considering factors such as:

• the extent and seriousness of each defendant’s breach
• the duration and intensity of each defendant’s contribution to the harm
• any relevant conduct by the claimant (e.g., contributory negligence)

For divisible injuries, apportionment is reflected in the claimant’s award against each defendant. For indivisible injuries, apportionment occurs between defendants after judgment or settlement by way of contribution. Where the claimant was contributorily negligent (Law Reform (Contributory Negligence) Act 1945), the court first reduces the claimant’s damages and then apportions the reduced sum between defendants.

Worked Example 1.8 (recalled)

C obtains £100,000 from D1. D1 is 70% to blame and D2 30% to blame.

Answer:
D1 may recover £30,000 from D2 via contribution so that D1 ultimately bears £70,000 and D2 £30,000.

Worked Example 1.9

P suffers an indivisible back injury in a collision caused by D1 (poor lookout) and D2 (excess speed). P was not wearing a seatbelt; the court finds 15% contributory negligence.

Answer:
P’s damages are reduced by 15% and assessed at £85,000 (from £100,000). P may recover the full £85,000 from either D1 or D2. If D1 pays in full and the court allocates fault D1: 60%, D2: 40%, D1 can recover £34,000 from D2 under the Contribution Act (40% of £85,000).

Novus Actus Interveniens and Multiple Causes

A novus actus interveniens (new intervening act) may break the chain of causation and relieve a defendant of liability for subsequent harm. However, where multiple defendants are independently negligent and their acts combine to cause a single injury, each remains liable for the whole loss unless the injury is divisible.

Key Term: novus actus interveniens
A new, independent act that breaks the chain of causation, so the original defendant is not liable for harm occurring after the intervening act.

Courts ask whether the intervening act was reasonably foreseeable and whether it was sufficiently independent to displace the original negligence as a cause. Instinctive rescue rarely breaks the chain; negligent treatment after injury will not normally break the chain unless it is grossly improper. Conversely, a highly unusual, independent act may break the chain.

Worked Example 1.10

Q negligently blocks a tunnel exit, causing hazard. A police inspector orders R to drive against traffic to close the tunnel. R is hit and injured.

Answer:
The inspector’s instruction was an unforeseeable intervening act that broke the chain of causation from Q to R’s injuries. Q is not liable for R’s injury. In contrast, in foreseeable follow‑on collisions at an accident scene, later negligent drivers may not break the chain; each negligent driver can be liable, with contribution between them.

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• Joint and several liability allows a claimant to recover full damages from any defendant responsible for an indivisible injury.
• The Civil Liability (Contribution) Act 1978 enables courts to apportion damages between tortfeasors based on their responsibility.
• The doctrines of material contribution and material increase in risk allow liability where causation cannot be precisely determined.
• Divisible injuries are apportioned between defendants; indivisible injuries result in joint and several liability.
• Novus actus interveniens may break the chain of causation and end a defendant’s liability for subsequent harm.
• In mesothelioma claims involving multiple exposures, Compensation Act 2006, s3 makes each responsible defendant liable in full to the claimant, with apportionment addressed by contribution.

Key Terms and Concepts

• joint and several liability
• contribution
• divisible injury
• indivisible injury
• material contribution
• material increase in risk
• novus actus interveniens