"LAW AND FACT IN JURY TRIALS. 1 55 expert witnesses to fact. What is their function? It is just this, of judging facts. They are called in because they are men of skill and can interpret phenomena which other men cannot, or cannot safely interpret. They judge the phenomena, the appear- ances, or facts which are presented to them, and testify to that which in truth these signify or really are; or they estimate quali- ties and values. We say that they testify to opinion. In truth, they are judging something, and testifying to their judgment of fact. It is perfectly well settled in our law that such opinions or judgments are merely those of a witness, they are to aid the jury or the judge of fact, and not to bind them ; the final judgment is for the jury,^ and, unquestionably, the judgment is one of fact. This is clearly expressed in Germany, where the expert appears to have the final authority which we allow only to the jury: " Experts judge only as to the relation of phenomena perceived by the senses to general rules of their art or science, but not at all as to the relation of a fact to legal truths (Rechtswahrheiten) ; that is merely the judge's affair. ... In contrast with his judgment, what the expert decides is simply a fact, no more nor less than a mere witness's declaration, and this fact, like every other, the judge has to refer to the appropriate rule of law. For this reason experts are called judices facti, — judices as opposed to ordinary witnesses, judices facti, because they do not judge as to the law, but their judgment or opinion only gives as its result a fact." ^ The nature of the operation and the true character of the result are evidently just the same, whether it be the judgment of the witness or of the jury that is final. It is in either case a judgment of fact. We have thus noticed a tertium quid, the process of reasoning, which we have set aside as relating to method. A further thing was brought to notice in the passage from Littleton's Case,^ viz., " matter of evidence." The jury, it was there said, " ar^ not [by a special verdict] to leave matter of evidence to the court to adjudge ; " they are themselves " to adjudge upon that evidence concerning matter of fact." 1 Head v. Hargrave, 105 U. S. 45 ; 3 Harv. Law Rev. 301-2 ; and so in modern times in France; Bonnier, Preuves, 4th ed. sect. 119. 2 Dr. W. H. Puchta in Zeitschrift fiir Civilrecht und Prozess, iii. 57. Compare Das Archiv. fiir die Civilistische Praxis, xxvi. 255-6. For these references I am indebted to my friend, Mr. Fletcher Ladd. See also Bonnier, Preuves, ubi supra. 8 Ante, p. 150.
