Eggshell Plaintiff Rule

The eggshell plaintiff rule (also called the thin skull rule or eggshell skull rule) is a well-established tort principle that a defendant takes the plaintiff as they find them. If the defendant's tortious conduct causes harm to a plaintiff who has a preexisting condition or vulnerability that makes the resulting injury more severe than it would be for an ordinary person, the defendant is liable for the full extent of the injury — not just the injury that would have occurred to a normal person.

The doctrine's name comes from a hypothetical: if a defendant negligently bumps a person whose skull is as thin as an eggshell, and the person suffers a fatal skull fracture rather than a minor bruise, the defendant is liable for the death. It does not matter that a normal person would have suffered only a bruise.

The rule operates as a limit on the proximate cause defense. While proximate cause generally limits liability to foreseeable harms, the eggshell plaintiff rule holds that the extent or severity of the harm need not be foreseeable — only that some harm to the plaintiff was foreseeable. Once the defendant's conduct creates a foreseeable risk of harm, the defendant is liable for all resulting harm, even if unexpectedly severe.

The rule applies to physical conditions (hemophilia, brittle bones), psychological conditions (preexisting PTSD that is exacerbated), and financial circumstances (a plaintiff who loses more income because they had a higher-paying job). The policy rationale is that it would be unjust to reduce a plaintiff's recovery simply because they happened to be more vulnerable.

This rule is frequently tested alongside proximate cause on torts exams. When an exam question describes a plaintiff with an unusual susceptibility, students should immediately think of the eggshell plaintiff rule and explain that foreseeability of the extent of harm is not required.