Define: Thin Skull Rule

The Thin Skull Rule, also known as the Eggshell Skull Rule or the Eggshell Plaintiff Rule, is a legal doctrine in tort law that states that a defendant is liable for all the harm caused to the plaintiff, even if the plaintiff’s pre-existing condition or susceptibility to injury was unknown or unforeseeable. In essence, it means that a defendant must take the plaintiff as they find them, regardless of any unusual or fragile condition that may increase the severity of harm suffered. The rule is based on the principle that defendants should be held accountable for the full extent of their wrongful actions, regardless of the particular vulnerability of the plaintiff. Thus, if a defendant’s negligent conduct causes harm to a plaintiff with a pre-existing medical condition or susceptibility to injury, the defendant is still liable for the resulting damages, even if the harm is more severe than it would be to an average person.

Eggshell skull, In criminal law and the law of tort, the thin skull rule states that you must take your victim as you find him. It means that the defendant cannot escape liability if the victim suffers more harm than would otherwise be expected due to, for example, an underlying medical condition, or unusually sensitive disposition. In legal causation, the thin skull rules operates in such circumstances to prevent the chain of causation from being broken.

In the case of Smith v. Leech Brain & Co., an employee in a factory was splashed with molten metal. The metal burned him on his lip, which happened to be premalignant tissue. He died three years later from cancer triggered by the injury. The judge held that as long as the initial injury was foreseeable, the defendant was liable for all the harm.

The term implies that if a person had a skull as delicate as the shell of an egg, and a tortfeasor who was unaware of the condition injured that person’s head, causing the skull unexpectedly to break, the defendant would be held liable for all damages resulting from the wrongful contact, even if such damages were not reasonably foreseeable, or the tortfeasor did not intend to cause such a severe injury.

An intervening cause is typically an exception to the Eggshell Skull rule. If an injury is not immediate, but a separate situation agitates the injury, the tortfeasor is not liable. For example, if A assaults B, and B is hauled away on a stretcher, where he is struck by lightning, even though A’s actions had caused B to be at the place and time of the bolt of lightning, the Eggshell Skull rule does not apply.

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This glossary post was last updated: 29th March, 2024.