Eggshell skull
The eggshell skull doctrine is a doctrine applied in both tort law and criminal law under which a defendant will be held responsible for all the consequence of his action, even if the plaintiff in a civil case or the victim in a criminal case had a preexisting medical condition or other vulnerability, such as if the plaintiff's skull is as fragile as an eggshell. This doctrine is often used in battery litigation.
A famous case that invoked the eggshell skull doctrine is Vosburg v. Putney, decided by a Wisconsin court in 1891, which a student kicked another student in the shin, causing serious injury that he did not foresee because the victim had a preexisting condition. The court decided that the student was fully liable even if he did not intend to cause serious harm. In 2001, an Oregon case Fuller v. Merton ruled that if eggshell skull doctrine is applicable in a case the presiding judge must inform the jury about the doctrine.
It is controversial whether the eggshell skull doctrine should be applied to severe mental distress ("eggshell psyche"), due to that psychological injury can manifest in physical injury, and purely mental injury can be faked. The past cases on this issue have been inconclusive.