A civil-law concept defining a rule, doctrine, or procedural mechanism used to resolve private disputes. It applies when its legally specified conditions are satisfied and produces defined consequences in adjudication or settlement. It does not apply where required elements or prerequisites are not met. It materially affects rights, obligations, or available remedies in civil controversies. The concept is generally stable, though statutory and doctrinal refinements may occur over time.

Principle

The responsible actor is accountable for all foreseeable and unforeseeable harm once his wrongful act is a substantial factor in producing injury; preexisting fragility does not reduce the defendant’s obligation to compensate.

Demonstration

A driver negligently rear-ends a bicyclist who, unknown to the driver, has a preexisting bone disease; the bicyclist suffers a catastrophic fracture far worse than an average person would have had — the defendant remains liable for the full damage.

Misapplication

Using the rule to claim full liability where the plaintiff’s preexisting condition was the sole cause of harm and the defendant’s act was only a trivial or unrelated contribution.

Consequence

Victims with heightened vulnerability receive complete compensation for harms caused by another’s wrongful act, preventing defendants from escaping responsibility by citing plaintiffs’ frailties.

Reversal

Treating plaintiffs as if they had typical resilience and reducing damages because a ‘normal’ person would not have suffered as much; this inversion shifts loss to the injured party.

Boundary

Applies in negligence and intentional-tort contexts where the defendant’s conduct is a legal cause of injury; it does not convert wholly independent illnesses into defendant-caused harms nor apply where causation is absent.

Semantic Tension

Tension exists between this rule and proximate cause doctrines that limit liability to foreseeable harms; courts reconcile by asking whether the type of harm was a consequence of the defendant’s act even if its extent was unforeseeable.

Synthesis

The Eggshell Plaintiff Rule integrates causation and liability: once wrongful conduct materially contributes to harm, a defendant bears full responsibility for the real-world outcome, including amplified injury due to the plaintiff’s preexisting vulnerability.