U.S. Supreme Court
Davis v. United States, 160 U.S. 469 (1895)
Davis v. United States
Submitted October 30, 1895
Decided December 16, 1895
160 U.S. 469
If it appears on the trial of a person accused of committing the crime of murder that the deceased was killed by the accused under circumstances which, nothing else appearing, made a case of murder, the jury cannot properly return a verdict of guilty of the offense charged if, upon the whole evidence, from whichever side it comes, they have a reasonable doubt whether, at the time of killing, the accused was mentally competent to distinguish between right and wrong or to understand the nature of the act he was committing.
No man should be deprived of his life under the forms of law unless the jurors who try him are able, upon their consciences, to say that the evidence before them, by whomsoever adduced, is sufficient to show beyond a reasonable doubt the existence of every fact necessary to constitute the crime charged.
The plaintiff in error was indicted for murder, tried in the court below, and convicted. In the opinion of this Court, the issue brought here for decision is stated as follows:
court below instructed the jury that the defense of insanity could not avail the accused unless it appeared affirmatively, to the reasonable satisfaction of the jury, that he was not criminally responsible for his acts. The fact of killing being clearly proved, the legal presumption, based upon the common experience of mankind, that every man is sane, was sufficient, the court in effect said, to authorize a verdict of guilty although the jury might entertain a reasonable doubt upon the evidence whether the accused, by reason of his mental condition, was criminally responsible for the killing in question. In other words, if the evidence was in equilibrio as to the accused's being sane -- that is, capable of comprehending the nature and effect of his acts -- he was to be treated just as he would be if there were no defense of insanity or if there were an entire absence of proof that he was insane. "