Opinion by

Two of the jurors called in this case were challenged by the Commonwealth for cause. The first two complaints of the appellant are that the challenges were sustained. The first juror, when examined on his voir dire by counsel for the prisoner, stated that, though he had formed an opinion as to the guilt or innocence of the accused, he could and would render a verdict according to the evidence, if sworn as a juror in the case; but, in answer to a question Toy the court, before he was passed over to the Commonwealth, he said it would require strong evidence to change that opinion, and that he could not lay it aside until he had heard evidence enough to remove it. Upon Ms examination by counsel for the Commonwealth, he said he would take his formed opinion with Mm into the jury box, and would keep it until he heard evidence to contradict or offset it. He was thereupon challenged for cause, and excused. What his opinion was, does not appear; but it did clearly appear out of Ms own m outh that if he had been sworn as a juror, he would have taken his seat in the box with a formed opinion that he could not lay aside until he had heard “evidence enough to remove it.” In the trial of cases, and especially capital cases, the great *413concern of counsel as well as of courts, should always be to secure jurors free from feeling, prejudice or opinions formed as to the questions at issue; for only such jurors can be safely trusted to return verdicts based upon evidence alone. The challenge of a juror for cause is addressed to the trial judge, and much weight must be given to his judgment in passing upon it. In exercising his discretion as to the fitness of a juror to serve, he has the juror before him, and much latitude must be left to him; and the weight to be given to the answers of a juror when examined on his voir dire is not to be determined exclusively by his words as we read them in the printed record. They are first to be weighed by the trial judge who sees and hears the juror, and, in the exercise of a wide discretion, may conclude that he is not competent to enter the jury box for the purpose of rendering an impartial verdict, notwithstanding his words to the contrary: Ortwein v. Com., 76 Pa. 414; Clark v. Com., 123 Pa. 555; Com. v. Roddy, 184 Pa. 274; Com. v. Eagen, 190 Pa. 10; Com. v. Spahr, 211 Pa. 542; and nothing short of palpable error will justify a reversal of a trial judge in passing upon a challenge for cause: Com. v. Crossmire, 156 Pa. 304. No such error is disclosed by the first assignment, and it is therefore dismissed. The second juror was challenged by the Commonwealth because he stated that he would not convict of murder of the first degree on circumstantial evidence, adding “Circumstantial evidence could not be strong enough for me to convict a man of murder in the first degree.” The second assignment is so utterly without merit that it is dismissed without comment.

By the third, fourth and fifth assignments the court is charged with error in not directing that alleged improper remarks of the district attorney be placed upon the record, in not directing a juror to be withdrawn after they were made, and in not instructing the jury to disregard them. It is sufficient to say that it does not appear from the record what the remarks were, nor that *414any request wás . made for the withdrawal of a juror, and the said assignments are therefore dismissed.

No complaint is made of the inadequacy of the charge, nor of any error in it as to the defense of insanity, except that portion of it complained of by the eighth assignment. The court was therefore not required to affirm defendant’s fourih and fifth points. The answers to them, in view of what was said in the general charge, were sufficient: Com. v. McManus, 143 Pa. 64; Com. v. Danz, 211 Pa. 507. A s to the- defense of insanity the jury were instructed that the burden of proving it was upon the defendant, and that evidence which created only a mere doubt or seasonable doubt as to sanity was insufficient to justify acquittal. This instruction is the subject of the eighth assignment. . We are again called upon to say that such instruction was correct, though we ought not to be required to do so after what was distinctly said upon a review of well considered cases, in Com. v. Molten, 230 Pa. 399. In referring to the defense of insanity set up in chat case, we said: “It is not, however, sufficient that the evidence had merely raised a doubt as to his insanity, for to doubt is to not believe, and nothing but belief that the prisoner was actually insane at the time ol the commission of the offense charged against him could have justified the jury in acquitting him on that ground. Such a belief under the humane rule of our eases, is one that results from a fair preponderance of the evidence.” The language of the trial judge complained, of in the present case, was, “With this burden of proof upon the defendant, evidence which creates only a mere doubt, or a reasonable doubt, as to his sanity, is insufficient to justify his acquittal. The jury must be satisfied by fairly preponderating evidence.” We need not now review the cases cited in the Molten casé as sustaining this instruction. A brief reference to two or'three of them will suffice. In Ortwein v. Com., supra, the chioi: question in the case arose under the fifth point of the prisoner, which was, “If the jury *415have a reasonable doubt of the sanity of the prisoner at the time of the killing, they cannot convict.” This was refused by the court below, and in holding that the refusal of the point was correct it was said, “A reasonable doubt of the fact of insanity cannot, therefore, be a true basis of the finding of it as a fact and as a ground of acquittal and of legal custody. To doubt one’s sanity is not necessarily to be convinced of his insanity....... Merely doubtful evidence of insanity would fill the land with acquitted criminals. The moment a great crime would be committed, in the same instant, indeed often before, would preparation begin to lay ground to doubt the sanity of the perpetrator. The more enormous and horrible the crime, the less credible, by reason of its enormity, would be the evidence in support of it; and proportionately weak would be the required proof of insanity to acquit of it. Even now the humanity of the criminal law opens many doors of escape to the criminal. Then a wider door would be opened by the doubtful proof of insanity made still more open by the timidity of jurors, their loose opinions on the subject of punishment, and their common error that the punishment is the consequence of their finding of the truth of the facts, instead of the consequence of the commission of the crime itself. The danger to society from acquittals on the ground of a doubtful insanity demands a strict rule. It requires that the minds of the triers should be satisfied of the fact of insanity.” This rule was reannounced shortly afterwards in Meyers v. Com., 83 Pa. 131, where it was said, through Mr. Chief Justice Agnew : “A reasonable doubt of the fact of insanity, on the other hand, is not sufficient to acquit upon a defense of insanity. This has been held in several cases: Ortwein v. Com., 26 P. F. Smith 414; Lynch v. Com., 27 Id. 205; Brown v. Com., 28 Id. 122. Sanity being the normal condition of men, and insanity a defense set up to an act which otherwise would be a crime, the burden rests upon the prisoner of proving his abnormal condition. But the *416evidence of this need Toe only satisfactory — and the conclusion such as faiiily results from the evidence.” Another case to whicib reference may he made is Com. v. Gerade, 145 Pa. 289. In the comparatively recent case of Com. v. Lee, 226 Pa. 283,. we said, through our Brother Stewart : “A reasonable doubt of the fact of insanity will not operate to acquit when this defense is set up.” The correct rule was followed by the court below in that portion of the charge complained of by the eighth assignment, and it is therefore dismissed.

In referring to Ms notes of testimony the trial judge distinctly told the j ury that they were to he guided by their own recollection of it, and not by his reference to it, if he erred in quoting it. This leaves the ninth, tenth, eleventh and twelfth assignments without merit. Upon consideration of the -whole record, no error is discoverable. It remains, therefore, only to say that the judgment is affirmed and that the record he remitted to the court beloW for the purpose of execution.