7. Damage: causation and remoteness

Damage Caused by the Breach

Two stages of damage: Once a plaintiff proves that the defendant owed a duty of care and breached that duty, one vital hurdle remains: proving damage. The plaintiff must show that the defendant is responsible in law for the harm suffered. This involves two distinct legal questions: causation in fact, and remoteness of damage.

Causation in Fact: The 'But-For' Test

The basic rule: Causation in fact asks whether the defendant’s careless act actually produced the plaintiff’s injury. The primary method used by the courts to answer this is the 'but-for' test: but for the defendant’s negligent conduct, would the plaintiff have suffered the harm? If the harm would not have occurred without the defendant's act, then the breach caused the harm.

Failing the test: If the damage would have happened anyway, the breach is not the cause of the injury. In Barnett v Chelsea and Kensington Hospital Management Committee, a night watchman went to hospital vomiting after drinking poisoned tea, but the doctor on duty refused to examine him and sent him home. The man died a few hours later. The hospital was in breach of duty, but medical evidence showed that the poison was so advanced that proper treatment could not have saved him. Because he would have died even without the doctor's neglect, the claim failed on causation.

Medical omissions: Similarly, in Robinson v Post Office, the plaintiff suffered a leg injury due to his employer’s negligence and required an anti-tetanus injection. The doctor administered the injection without performing an allergy test first, and the plaintiff suffered a severe reaction. The employer was held liable for the overall injury, but the doctor was not liable for failing to test. The court found that the injection was urgently required and an allergy test would not have revealed the reaction in time to prevent it.

Multiple wrongdoers: The 'but-for' test works well when dealing with a single defendant and an isolated breach, but it struggles with multiple wrongdoers. Suppose two individuals independently and negligently start fires that merge at the same time to burn down a plaintiff's house, and either fire alone was sufficient to destroy it. A strict 'but-for' test would let both escape liability, because the house would have burned down regardless of either person's fire. To prevent injustice, courts set aside the test in such situations and hold both wrongdoers fully liable, leaving them to seek financial contribution from one another.

Remoteness of Damage: Limiting Liability

The scope of liability: A careless act can set off a chain of events that stretches indefinitely into the future. Remoteness of damage is the legal mechanism that sets a boundary on how far liability can extend. Even where a breach passes the 'but-for' test, the defendant is liable only for harm that the law does not consider too remote.

The old direct consequences rule: Under the older common law rule laid down in Re Polemis and Furness, Withy & Co Ltd, a defendant was liable for all direct consequences of a negligent act, regardless of whether the specific kind or extent of harm was foreseeable. In that case, stevedores dropped a wooden plank into a ship's hold, producing an unexpected spark that ignited petrol vapours and destroyed the vessel. Even though the fire could not reasonably have been anticipated, the defendants were held liable simply because the destruction flowed directly from the falling plank.

The modern rule of reasonable foreseeability: The Privy Council rejected the direct consequences test in The Wagon Mound (No 1), declaring Re Polemis and Furness, Withy & Co Ltd bad law. The defendants carelessly spilled furnace oil into Sydney Harbour, which drifted over to the plaintiff’s wharf where welding operations were taking place. Molten metal set waste cotton floating in the oil on fire, causing extensive damage to the wharf. Although physical fouling of the slipways was foreseeable, scientific opinion at the time held that oil spread thinly over water would not ignite. The court held that the defendants were not liable for the fire damage because that kind of harm was not reasonably foreseeable. Following The Wagon Mound (No 1), the test of reasonable foreseeability governs all three elements of negligence: duty, breach, and damage.

The Eggshell Skull Rule

Take your victim as you find them: While the kind of damage must be reasonably foreseeable, the defendant does not need to foresee the full extent or severity of that harm. Under the eggshell skull rule, a wrongdoer must take their victim as they find them. In Dulieu v White & Sons, Kennedy J explained that if a person is negligently injured, it is no defence to argue that the victim would have suffered less harm or no harm at all had they not possessed an unusually thin skull or a weak heart.

Pre-existing vulnerabilities: This rule applies whenever a victim has a pre-existing medical or psychological condition. In Smith v Leech Brain & Co Ltd, an employee suffered a minor burn to his lip from molten metal due to his employer’s negligence. The burn triggered an underlying, pre-malignant condition that developed into fatal cancer. The court held the employer liable for the death; because a burn injury was foreseeable, the employer had to answer for the full extent of the harm caused by the victim's sensitivity. Similarly, in Love v Port of London Authority, the court reaffirmed that a defendant must take the plaintiff as found, including any vulnerable psychological state that worsens the ultimate outcome of the injury.