What is the standard for a tortfeasor to bring a claim of intentional indifference to the medical needs of a prisoner under the Eighth Amendment?

Estelle v. Gamble (1976) 429 U.S. 97, 97 S.Ct. 285, 50 L.Ed.2d 251, set forth the standards applicable to a claim that the medical needs of a prisoner have been ignored. In that case the United States Supreme Court held that "deliberate indifference to serious medical needs of prisoners constitutes the 'unnecessary and wanton infliction of pain' ... [citation omitted] proscribed by the Eighth Amendment." (Estelle v. Gamble, supra, 429 U.S. at p. 104, 97 S.Ct. at p. 291.) The court went on to state, however, that not every claim of inadequate medical care rises to the level of cruel and unusual punishment. Specifically, "a complaint that a physician has been negligent in diagnosing or treating a medical condition does not state a valid claim of medical mistreatment under the Eighth Amendment." (Id., at p. 106, 97 S.Ct. at p. 292.)