The accused, who had separated from his wife, Ida Marie Thiele, saw her pass the house in Villisca at which he was stopping. He immediately ran across the street and stabbed her with a knife three times. From the wounds so inflicted she died within a few minutes.. At the trial, the defense of insanity was interposed.
*661i. insanity: proof. *660The evidence tended to show that, for some time previous, the defendant acted peculiarly and talked ■ incoherently; would get excited without cause, and frequently cry; was often dejected, and would look wild out of his eyes sometimes, and at others foolish; would run in doing ordinary work, and exercised no judgment in accomplishing what he undertook; had frequently claimed the Bible gave him the right to kill his wife; and the physicians testified that there was a depression in his skull which caused a derangement in the action of the brain. Nine nonexpert witnesses and three physicians expressed the opinion that he was insane. As bearing on this defense,, the court instructed the jury that: “In considering this question of the insanity of the accused, you are to bear in' mind that the presumption of the law is that he was sane. The burden is upon him to establish that at the time of the killing of said Ida Marie Thiele, if he did kill her, he was in such a state of insanity as will excuse the act. And if the evidence goes no further than to show that such a state of mind was possible or even probable, it is not sufficient. It must be sufficient to overcome the legal presumption of sanity, and satisfy you by a fair preponderance of the evidence that he was not sane. The defense of insanity is one which should be thoughtfully, thoroughly,, and dispassionately considered by you. You should indulge in no prejudice against it, but you should give it a candid and fair consideration, with an honest design to-reach the very truth of the matter.” That the burden was upon the defendant to establish his insanity at the *661time of the killing by a preponderance of the evidence is not questioned, nor could it be in this stare. State v. Fetter, 32 Iowa, 49; State v. Geddis, 42 Iowa, 264; State v. Bruce, 48 Iowa, 530; State v. Trout, 74 Iowa, 545; State v. Mewherter, 46 Iowa, 88; State v. Van Tassel, 103 Iowa, 11; State v. Robbins, 109 Iowa, 650.
The critcism of the instruction is (1) that in effect it treats the presumption of sanity as having some weight as evidence, and (2) that the degree of proof exacted is more than a mere preponderance of the evidence. A similar instruction, from which the objectionable part of this may have been copied, was condemned-in State v. Jones, 64 Iowa, 349. Indeed, a comparison of this with the instruction in the Jones Cuse indicates that the very defect pointed out in the latter is here emphasized by omitting “merely” before “probable.” When analyzed, what might the jury reasonably have understood from the language used? If the evidence made it appear that the defendant might possibly have been insane, this would not entitle him to an acquittal, for, at most, only a reasonable doubt would thereby be raised as to his sanity. This was correct under the decisions of this state, though contrary to the conclusion reached by the Supreme Court of the United States in Davis v. U. S., 160 U. S. 469 (16 Sup. Ct. Rep. 353, 40 L. Ed. 499), a case of first impression.
a. insanity: instmction. In saying he was not entitled to an acquittal if the evidence proved him probably insane, there was error. The existence of disease in the brain of a living being is seldom the subject of demonstrated or direct pr00f. Of necessity, reliance must be placed on outward manifestations, and from these the inference drawn as to the condition of the brain. The conduct and speech of a party are not always the true index of mental capacity or incapacity. Cases of feigned insanity • are not infrequent, and about all courts are able to do in most cases is to speak from the evidence as to the probability or *662improbability of the accused having been insane at the time under investigation. By saying insanity is probable is meant, as .understood in common parlance and from the definition of lexicographers, that there is more evidence of insanity than against it, or better reason to believe the defendant insane than to suppose him sane. State v. Jones, supra; State v. Trout, 74 Iowa, 545; Kelch v. State, 55 Ohio St. 146 (45 N E. Rep. 6, 39 L. R. A. 737, 60 Am. St. Rep. 680.)
3. Same. But the court in effect told the jurors that, even if it were made to appear probable that defendant was insane, he must be held accountable for his act. And more, that such probability would not alone overcome the presumption of sanity. The defendant must have gone still farther and introduced evidence to overcome this presumption, and -then, in addition thereto,, satisfy the jury of his insanity by a fair preponderance of the evidence. Even if the presumption were to be accorded some probative force rather than treated as a mere rule concerning the burden of proof, it ought not to be offset in this way against evidence establishing the probability of defendant’s insanity. Sanity is the normal condition, and the presumption that it exists goes no farther than the assumption, for the purposes of the trial, that the accused is not different in this respect from other men. The Jaw does not undertake to measure the precise amount of evidence which, when undisputed, will rebut this assumption and justify the conclusion that a person is abnormal, save that it must be enough to convince the understanding: But the jury are not to be told that the presumption is of no consequence in weighing evidence, or, as was requested by appellant, that it is not “to weigh the presumption of defendant’s sanity against any measurable amount of evidence of insanity”; for an appreciable weight of evidence is required to establish the existence of an abnormal condition of the mind. Not until the evidence indicates that *663the existence of insanity is probable, that is, is such as to render this conclusion more reasonable than a contrary inference, has the assumption that the party under investigation was in a normal state been overcome. The particular vice of the instruction is that it negatives this proposition, and tells the jury that even evidence producing this effect does not overcome the bare presumption of sanity; that still more must be introduced to accomplish this, and, in addition thereto, the defense established by ■ a preponderance of evidence. The error is too manifest to require further elucidation. But the state urges that the fault found is purely technical, and not likely to have prejudiced the defendant. Our learned predecessors twenty years ago were unable to agree upon this point, or upon a proper construction of a like instruction in the tTones Case. This fact alone is sufficient warrant for thinking that the jurors might have construed the charge logically and as it was written.
There is nothing in the presumption of sanity demanding special explanation. Any juror of ordinary comprehension understands what is meant by it, and it is sufficient if, in simple and direct language, the jury are advised upon which side is the burden of proof, and the quantum exacted by the law. Because of the error in this instruction, the judgment is reversed and the cause remanded.