The truth of the facts assumed by the ques tion is, in doubtful cases, a question for the jury, and if they find that the assumed facts are not proved, they should disregard the opinions based on such hypothetical ques tions, and the court will so instruct them; People v. Foley, 64 Mich. 148, 31 N. W. 94; Turnbull v. Richardson, 69 Mich. 400, 37 N. W. 499 ; but the court is not required to sub mit the matter to the jury unless there is some substantial evidence tending to estab lish the hypothesis ; Nave v. Tucker, 70 Ind. 15. If there is no testimony in the case tending to prove the facts assumed in the question, it is improper ; the facts must be proved or proof of them must be offered ; Turnbull v. Richardson, 69 Mich. 400, 37 N. W. 499; Hovey v. Chase, 52 Me. 304, 83 Am. Dec. 514; Muldowney v. R. Co., 39 Ia. 615 ; Reber v. Herring, 115 Pa. 599, 8 Atl. 830 ; Williams v. Brown, 28 Ohio St. 547; Quinn v. Higgins, 63 Wis. 664, 24 N. W. 482, 53 Am. Rep. 305 ; Woolner v. Spalding, 65 Miss. 204, 3 South. 583; Haish v. Payson, 107 Ill. 365.
The length of the question is to be regu lated, largely, by the discretion of the trial judge; Forsyth v. Doolittle, 120 U. S. 73, 7
Sup. Ct. 408, 30 L. Ed. 586; it has been held an error to permit it to be so long and com plicated as to confuse the witness or baffle his memory ; People v. Brown, 53 Mich. 531, 19 N. W. 172; Haish v. Payson, 107 Ill. 365; but to obviate this difficulty the court may require the question to be reduced to writ ing; Jones v. Portland, 88 Mich. 598, 50 N. W. 731, 16 L. R. A. 437. If unfair and mis leading, hypothetical cases assumed in fram ing questions are to be considered in deter mining whether or not a fair trial has been had; McFall v. Smith, 32 Ill. App. 463; but it cannot be expected that the interrogatory will include the proofs or theory of the ad versary, since this would require a party to assume the truth of that which he generally denies; Goodwin v. State, 96 Ind. 550. Hypo thetical questions cannot be asked of an or dinary observer; State v. Klinger, 46 Mo. 224; Russell v. State, 53 Miss. 367; Appeal of Dunham, 27 Conn. 192. And, as to this, a professional man, in a matter of which he has not made special study is doubtless re garded as an ordinary observer.
See EXPERT ; OPINION ; EVIDENCE.