Causation in Personal Injury Lawsuits under Personal Injury
1. Actual Cause (Cause-in-Fact)
Definition:
Actual cause asks: Would the injury have occurred "but for" the defendant’s conduct? If the answer is no, then the defendant’s conduct is an actual cause of the injury.
Key Test:
"But for" Test: The injury would not have occurred but for the defendant’s actions.
In some complex cases (e.g., where there are multiple causes), courts may also apply:
Substantial Factor Test: Was the defendant's conduct a substantial factor in bringing about the harm?
✦ Case Law Example:
Barnett v. Chelsea & Kensington Hospital Management Committee [1969] 1 QB 428
Facts: A man went to the hospital after drinking tea laced with arsenic. He was turned away without treatment and later died.
Held: The hospital was negligent in refusing treatment, but the man would have died anyway, as the poison was already in his system.
Importance: Demonstrates that negligence must actually cause the harm — since death was inevitable, causation failed.
2. Legal Cause (Proximate Cause)
Definition:
Even if actual causation is proven, a defendant may only be held liable if the injury was a foreseeable consequence of their conduct.
Key Question:
Was the harm within the scope of foreseeable risk created by the defendant’s actions?
Limitations:
Courts will limit liability where the harm is too remote or where an intervening act breaks the chain of causation (novus actus interveniens).
✦ Case Law Examples:
The Wagon Mound (No. 1) [1961] AC 388
Facts: Oil negligently spilled into a harbor caught fire, causing extensive damage.
Held: Though spilling oil was negligent, fire damage was not foreseeable.
Importance: Emphasizes that damages must be reasonably foreseeable — no proximate cause without foreseeability.
Smith v. Leech Brain & Co [1962] 2 QB 405
Facts: Plaintiff’s husband was splashed with molten metal due to employer’s negligence. The burn triggered a latent cancer condition, and he died.
Held: The injury (burn) was foreseeable; the extent (death from cancer) need not be.
Importance: The defendant must "take the victim as they find them" (eggshell skull rule). If the initial harm is foreseeable, they are liable for all resulting consequences.
3. Intervening Acts (Novus Actus Interveniens)
Sometimes an independent act occurs after the defendant's negligent act, which contributes to the harm. Courts assess whether this new act breaks the chain of causation.
✦ Case Law Example:
Knightley v. Johns [1982] 1 WLR 349
Facts: A police officer negligently sent another officer the wrong way into a tunnel, leading to a fatal accident.
Held: The second officer's actions were an intervening act that broke the chain of causation from the original accident.
Importance: The defendant is not liable if a new, unforeseeable act causes the harm.
4. Multiple Causes & Joint Liability
Where multiple parties contribute to the harm, causation principles are adjusted:
✦ Case Law Example:
Fairchild v. Glenhaven Funeral Services Ltd [2002] UKHL 22
Facts: Several employers exposed the claimant to asbestos, leading to mesothelioma. It was impossible to tell which exposure caused the disease.
Held: Each employer materially increased the risk of harm and was held jointly liable.
Importance: In some complex cases, courts may relax the causation standard to ensure justice.
Summary Table
| Element | Test Applied | Key Case | Principle |
|---|---|---|---|
| Actual Cause | "But for" or substantial factor | Barnett v. Chelsea & Kensington | Harm must directly result from the defendant's act |
| Legal Cause | Foreseeability | The Wagon Mound (No. 1) | Harm must be a foreseeable consequence |
| Eggshell Skull Rule | Take your victim as you find them | Smith v. Leech Brain | Full liability even if the injury is unusually severe |
| Intervening Acts | Novus actus interveniens | Knightley v. Johns | Chain of causation may be broken |
| Multiple Causes | Material increase in risk | Fairchild v. Glenhaven | Shared liability despite causal uncertainty |
Conclusion
Causation in personal injury law ensures that only those responsible for causing harm are held liable. The claimant must prove both factual (actual) causation and legal (proximate) causation. Courts sometimes adjust the rules to ensure justice, especially in cases involving multiple causes, latent conditions, or intervening events.
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