In the law of evidence no principle is more familiar than that which ordinarily excludes the opinion of a nonexpert witness. One who is called to testify is generally restricted to proof of facts within his personal knowledge, and is not permitted to express his opinion concerning matters which the jury are required to decide. Omne sacramentum debet esse de certa scientia. McKelvey says, “Upon the question of the. existence or nonexistence of any fact in issue, whether a main fact or evidentiary fact, the opinion of a witness as to its existence or nonexistence is inadmissible.” Evidence, 172. The principle is abundantly sustained by our decisions. Mullinax v. Hood, 174 N. C., 607; Deppe v. R. R., 154 N. C., 523; Gilliland v. Board of Education, 141 N. C., 482; Pump Co. v. R. R., 138 N. C., 301; Cogdell v. R. R., 130 N. C., 314.
In Mule Co. v. R. R., 160 N. C., 253, Dr. McMackin, an expert veterinarian, was asked to state his opinion as to the cause of a mule’s death, based upon His knowledge and experience and his post mortem examination. He answered, “My opinion is that the mule was jammed up in the ear.” The Court said: “This evidence was improperly admitted. The question required him to testify not only as to the condition of the mule when he examined him, which was proper, but to go further and give his opinion as to the existence of a fact which was almost, if not quite, the equivalent of the one directly involved in the issue. It would have been competent to have asked him if the death of the mule could have been caused by being jammed in the car, or, if the jury should find from the evidence that the mule had been jammed in the ear - and had received no other injury, could the death, in his opinion, be attributable to the jamming as its cause — that is, was it sufficient of itself to cause the death. A question similar to the one admitted in this case by the court was asked in Summerlin v. R. R., 133 N. C., 551, and excluded by the court, and we sustained the ruling, upon the ground that the witness was called upon to state a fact of which he had no personal or competent knowledge, and not merely the opinion of an expert. The opinion of the witness should be based upon facts admitted or found, or upon his personal knowledge, and not upon the assumption of the fact. The question should, therefore, be hypothetical or rather supposititious, in form, following the precedents as settled by our decisions. S. v. Bowman, 78 N. C., 509; S. v. Gole, 94 N. C., 958; S. v. Wilcox, 132 N. C., 1120, and Summerlin v. R. R., supra. The Court, in Hitchcock v. Burgett, 38 Mich., 501, held that “a physician cannot be asked his opinion as to the cause of an injury, judging merely *478from the condition in which, he found the patient, and without any knowledge as to how it took place.” See, also, National Union v. Thomas, 10 App. Cases (D. C.), 277; Carpenter v. E. T. Co., 71 N. Y., 574; Van Zandt v. Ins. Co., 55 N. Y., 179; Lumber Co. v. R. R., 151 N. C., 217, and cases cited at page 222.”
It is clear that the evidence excepted to was admitted through inadvertent disregard of this rule, and that the witnesses were permitted to make known their opinion and judgment on questions which should have been submitted exclusively to the determination of the jury. Other exceptions present serious questions which may not arise again, and we refrain from discussing them. For error in the admission of evidence, the defendants are entitled to a
New trial.