"The law has grown, and even if historical mistakes have contributed to its growth, it has tended in the direction of rules consistent with human nature. Many respectable writers agree that, if a man reasonably believes that he is in immediate danger of death or grievous bodily harm from his assailant, he may stand his ground, and that, if he kills him, he has not exceeded the bounds of lawful self-defense. That has been the decision of this Court. Beard v. United States, 158 U. S. 550, 158 U. S. 559. Detached reflection cannot be demanded in the presence of an uplifted knife. Therefore, in this Court at least, it is not a condition of immunity that one in that situation should pause to consider whether a reasonable man might not think it possible to fly with safety or to disable his assailant, rather than to kill him. Rowe v. United States, 164 U. S. 546, 164 U. S. 558.
Moreover, if the last shot was intentional and may seem to have been unnecessary when considered in cold blood, the defendant would not necessarily lose his immunity if it followed close upon the others while the heat of the conflict was on, and if the defendant believed that he was fighting for his life."
Brown v. United States, 256 U.S. 335 (1921) (opinion by Justice Holmes).