I concur with my brother HOGAN, but desire to add a few observations on the question whether we should disregard what we all agree was an error of law in admitting the testimony of the witness Snyder.
Our sole function in this case is to decide questions of law with which the unanimous affirmance by the Appellate Division has nothing to do. Of course, we are to consider the facts to determine the bearing of the law points and whether any errors of law committed on the trial were prejudicial to the defendant; but under our system of jurisprudence the determination of the defendant's guilt or innocence is the sole province of the jury. It is the defendant's right to have that determination made on legal evidence wholly uninfluenced by matters which the law says may not be considered to his prejudice. For us to convict the defendant upon conflicting evidence and thus to say that he was not harmed by prejudicial error is to disregard the forms of law, to *Page 88 assume arbitrary power, and to deprive the accused of his liberty upon our varying individual judgments instead of the judgment of the law.
There was a sharp conflict at the trial on the important question of fact, whether the words claimed to have been forged were written upon the defendant's typewriter. The People's case in that respect depends almost wholly on expert evidence, offered to show that certain alleged defects in the defendant's typewriter corresponded with defects in the typewritten words; and that evidence, so far as it was visualized for the jury, consisted of exhibits prepared by the People's expert. Of the thirteen similar defects testified to by him, two were variable and concededly may be eliminated, one was the slant of the letter "t," which the People's witnesses admitted was a common occurrence, and ten were due to alleged defects in the type. The People's expert witnesses who examined the type of the defendant's machine with a microscope were able to name five defects, which their testimony on cross-examination tended to show were common on used machines. Those defects existed in three letters most generally used. The photographs, ten diameters enlarged, are claimed to show five other defects, consisting of the letter "s" being heavy in the upper and lighter in the lower parts, the letter "a" being heavy in the lower and lighter in the upper parts, and an almost imperceptible swerve in one of the down strokes of the letter "m." Each of the defects alleged varies in the disputed writing and the two standards of comparison; and there are other differences between the standards and the disputed writing, which together with the differences in the defects in dispute may have resulted from defects in different typewriters, from different ribbons, from the way in which the writing was done, and conceivably even from the manner in which the enlarged photographs were produced. I do not say that to criticise or in any way to reflect upon the People's experts, but only to point out *Page 89 the extreme importance of confining the expert testimony within proper limits in a case admitting of such opportunity to err, and upon a question in the decision of which the jury had to depend almost wholly on such testimony both for the particular facts and for most of the conclusions therefrom.
Even assuming that the alleged eleven defects, variable as they were in extent and character in the disputed writing and the standards, had some resemblance to defects in the defendant's typewriter, the likelihood of similar defects in type recurring in another typewriter would depend on the dies from which they were made, on the process of manufacture, on the greater likelihood of particular parts, such as serifs, being broken by use, on the material composing the type, on the way in which the machine had been used, and doubtless on many other things which do not now occur to me; and yet the problem was sought to be determined by a so-called law of mathematical probability regardless of actual experience, physical facts or the element of human agency, and on the assumption manifestly false that a given thing was as liable to happen as not to happen. Upon selected data, which may or may not have been the ones involved in the problem, it was computed that the same slant of the letter "t" would occur once in 256 times, like computations were made as to each of the alleged defects and by compounding the results it was computed that all would occur in combination once in 4,000,000,000 times. Thus the happening of a past event was sought to be established not by witnesses of the fact, not by proof of the circumstances surrounding it or the causes contributing to it, but by an abstract doctrine of chances, which was put before the jury as a demonstration to a mathematical certainty.
So far from being a trivial incident to which no importance was attached at the trial, the evidence covers many pages of the record and in fact consisted of the *Page 90 entire testimony of a witness learned in the higher mathematics, summoned from a great university to testify. To the credit of the district attorney it should be said that he does not make the argument, too often made in this court by counsel, who against strenuous objection have succeeded in getting improper evidence before the jury, that no attention was paid to it. He asserts that it was proper to be considered by the jury and states the reason for its introduction as follows: "A large part of the cross-examination by appellant's counsel of the practical typewriter men called by the People as witnesses was devoted to an effort to establish by them that the several defects shown to exist in the type on appellant's typewriter were frequently found in typewriter type. * * * It was obviously intended to argue from this, that exactly the same condition as existed in the typewriter in question might reasonably be expected to be found with some frequency in other typewriters. There was thus brought into the case by the appellant the very proposition which the People sought to rebut by the testimony of Professor Snyder, namely, that the fact that the particular defects which existed here occurred in typewriter type with some degree of frequency, indicated a fair probability that other typewriters would show the same condition as existed in the appellant's typewriter." The evidence then based on actual experience and observation, that the defects in the defendant's typewriter discoverable by a microscopic examination were common in such machines, was to be overthrown by the testimony of a witness, who knew nothing on the subject from observation and experience, that to a mathematical certainty they would not recur with certain other assumed defects in another machine once in 4,000,000,000 times.
Of course, the combination of particular defects in one machine, if it existed, was the damaging fact against the defendant and if it were established that the eleven assumed defects actually existed in the defendant's typewriter *Page 91 and corresponded with the defects in the disputed writing, I should be prepared to agree that the fact in issue was so conclusively established as to render the error harmless; but a careful examination of the exhibits convinces me that upon this branch of the case the jury must have relied largely upon the conclusions of the experts and that in all probability they were profoundly impressed by the conclusion of Prof. Snyder that the assumed defects would not recur in another machine once in 4,000,000,000 times. Whilst the existence of the defects was merely assumed in the question put to the witness, it is going too far to assume that the jury so carefully analyzed the evidence as to distinguish between defects assumed in the abstract and those actually found to exist and to note the precise relation between the defects in the defendant's typewriter and those appearing in the disputed writing and the standards of comparison. The vice of the testimony consisted in its being purely an abstract theory having no relation to actual experience. The minds of the jury were thus diverted from the actual facts in issue and led into a maze of abstract theory and speculation, and it is not to be supposed that they perceived, what escaped the notice of the court and the district attorney, that there was no relation between the facts and the theory.
It cannot fairly be charged that the defendant's counsel have attempted to magnify a trivial circumstance, or an unimportant incident of the trial. They vigorously protested at the trial against the introduction of the evidence concerning the so-called law of mathematical probability and persisted in their objection to the very verge of showing disrespect for the court's ruling, and the effect of the adverse ruling upon the jury was heightened by such colloquies as the following:
"Defendant's Counsel: Isn't this purely speculation without any basis? *Page 92
"The Court: We have the testimony of this witness that it is a matter of mathematical accuracy." and later:
"Defendant's Counsel: I don't want to be too strenuous about this, but I do want to object to this testimony on the further ground that there is no foundation whatever for it; it is perfectly obvious that it rests entirely on speculation. If there was one machine in existence this rule would not apply at all; if there was more than one machine in operation, it might apply in some way; if there were ten thousand in operation —
"The Court: The suggestion is upon the very line I indicated a moment ago. It may appear it is too ridiculous for consideration, but the People claim everything from it. I think it is competent. As to the weight of the evidence, it is for the jury. I think I better hear it."
I am not certain what any intelligent person would have concluded without the aid of expert testimony or that the jury had such common sense and keen perception as to ignore the entire testimony of a witness of distinction introduced by the district attorney in the manner described for the purpose avowed, allowed over strenuous objection and characterized by a learned judge as competent but am of the opinion that the admission of this testimony was prejudicial to the defendant.
The trend of popular thought may be in favor of having the courts disregard the rules and forms of law in deciding appeals in criminal cases; but although we may seem to be far removed and secure from the arbitrary exercise of power, it should not be forgotten that it is the very essence of our boasted freedom that the citizen holds his life, liberty and property subject to the law only and not at the discretion of any individual, be he judge, executive or legislator.
I have not intended to suggest or countenance the view that erroneous rulings are per se cause for reversal or *Page 93 that new trials should be granted for technical, trivial or unsubstantial errors. Being convinced that the defendant has not had what the law accords him, a trial free from prejudicial errors of law, it is not for us to express any opinion as to his guilt or innocence, which must be determined by another jury.