Torts. Under the eggshell-skull rule, or thin-skull rule, a defendant is liable for all injuries caused by his tortious conduct, even if the plaintiff suffers an unusually high level of damage (e.g., due to a pre-existing vulnerability). The rule is supported by the axiom that “a defendant must take a plaintiff as he finds him.”
Vosburg v. Putney, 80 Wis. 523 (1891) is the seminal case on the eggshell-skull rule. In Vosburg, a school boy kicked another boy in the shin, in circumstances that made the kicking a battery. The kick would not have seriously injured a normal person, but the victim had an infection in his tibia and the kick aggravated the infection, causing serious injury. The court held the defendant liable for the entire damages. See also Cobige v. City of Chicago, 651 F.3d 780, 782 (7th Cir. 2011) (“A tortfeasor takes his victim as he finds him, and if a special vulnerability . . . leads to an unusually large loss, the wrongdoer is fully liable.”); Schmude v. Tricam Industries, Inc., 556 F.3d 624, 628 (7th Cir. 2009) (“If a tortfeasor inflicts a graver loss on his victim than one he would have expected because the victim had some pre-existing vulnerabiliy, that is the tortfeasor’s bad luck; you take your victim as you find him. That is the famous ‘eggshell skull’ rule of tort law.”); Prosser, Handbook the the Law of Torts § 43, at 261 (4th ed. 1987) (“[A] defendant is held liable when his negligence operates upon a concealed physical condition, such as pregnancy, or a latent disease, or susceptibility to disease, to produce consequences which he could not reasonably anticipate.”); Restatement 3d of Torts: Liability for Physical and Emotional Harm, § 31 (“When an actor’s tortious conduct causes harm to a person that, because of a preexisting physical or mental condition or other characteristics of the person, is of a greater magnitude or different type than might reasonably be expected, the actor is nevertheless subject to liability for all such harm to the person.”).