In Hays v. Viscome (1953) 122 Cal.App.2d 135, "the critical question in the case was whether plaintiff had suffered an injury which resulted in nerve pressure"--a type of injury with serious consequences--or an injury that did not result in nerve pressure, which would not have had those consequences. (Id. at p. 140.) The defense retained a physician and, after he examined the plaintiff, decided not to call him as a witness. Instead, it retained another physician who examined the plaintiff again and testified that there was nothing wrong with her. (Id. at p. 137.) The jury awarded the plaintiff only $ 700. (Id. at p. 136.) The Court of Appeal held that the trial court erred when it excluded evidence that the defense had obtained the first doctor's examination and then failed to call him as a witness and when it failed to instruct the jury that the failure to call him could support an inference that he would have given adverse testimony. (Id. at pp. 138-139.) In sum, the holding in Hays was that the the court's ruling prevented the jury from receiving evidence and instructions on which it could have based an inference that the defense hid evidence which could have led to a different verdict.