ROLAPP, District Judge,
after stating the facts, delivered the opinion of the court.
The errors assigned upon this appeal are all based upon testimony admitted into the record over defendant’s objection, and which appellant claims constituted prejudicial error. During the trial, Dr. Anderson, a witness for plaintiff, was asked the following hypothetical question: “Q. I would ask you, if a person during the major portion of her lifetime had been in the enjoyment of good health, except at times of confinement, and in case of suffering for some time with milk leg in the opposite leg to the one that may be injured; if a person in the enjoyment of health under such circumstances, should be on a train, and two trains collided, and if that person under those circumstances, in that collision, is thrown violently to the floor, with another person on her, and afterwards begins to menstruate, and a week later passes a. mass of substance about the size of an egg, after some days’ slight and then heavy menstruation — what, in your opinion, would that substance be, and what, in your opinion, would be the cause of its discharge from the patient? In addition, doctor, to those conditions which I have stated, a patient, *245having but a slight show of menstruation, rests a couple of nights and a day, and takes a drive of twenty-five miles in a buggy, and then rests another night, and returns that twenty-five miles in a buggy, and then rests another night and a portion of the following day, travels a couple of hours in a train, takes rest until 3:30 in the morning, takes train again and makes another run of about three hours, rides three or four miles in a street car, and rests all day, returns this three or four miles in a street car and takes train for probably another half hour, rides in á carriage a couple of miles, and rests all night, and the following day drives before dinner five miles, and in the afternoon back home, five miles, and finds during this time that menstruation has increased, goes to bed, and on the following day has a' miscarriage — what, in your opinion, doctor, has been the cause of that miscarriage?” This question was objected to because it did not contain all the material facts relating to the matter inquired 1 about. The objection was overruled, and the witness was permitted to answer. In this we think the trial court erred. This question omits several material facts which should have been made part of the question, and without which no fair expert answer could be expected. The question omitted to make any mention df plaintiff’s walk of a mile and a half, or of the fact that, notwithstanding her known pregnancy, she was menstruating on the evening of the accident, and that the same was daily getting worse, and accompanied with increasing pain, or that she concealed the fact, not even permitting her husband to be informed, although he was in her presence all the time, or of the fact that she was so weak that two or three days .after the accident, and two or three days before her miscarriage, she could hardly sit up in the wagon in which she then took a drive of fifty miles. We think that all these circumstances were very material ingredients of a hypothetical question, the purpose of which was to ascertain from a medical expert the causes which had produced plaintiff’s then very serious condition. At the time *246the question was asked, tbes© facts were all proven, were undisputed, and dearly material. Under sueb circumstances, a party is not permitted to select facts which, may be advantageous to him, and omit proven facts equally material, but not so beneficial to Ms cause, and upon such partial facts frame a hypothetical question to be submitted to an expert witness. The purpose of all judicial investigation is the ascertainment of truth. Such purpose is wholly frustrated if a party is permitted to exdude from a hypothetical question material undisputed facts.
“In a civil case all the undisputed facts of the case must be included in a hypothetical question, both as a matter of sound principle and of reason and justice. Neither party has a right to discard an important undisputed fact because the insertion of such fact may alter or vary the answer or opinion of the witness to the prejudice of such party.” People v. Vanderhoof, 71 Mich. 158, 39 N. W. 28; Levinson v. Sands, 81 Ill. App. 578; Davis v. State, 35 Ind. 496, 9 Am. Rep. 760; Vosburg v. Putney, 80 Wis. 523, 50 N. W. 403, 14 L. R. A. 226, 27 Am. St. Rep. 47.
We also think the court erred in permitting Mrs. Hansen, a non-expert witness for plaintiff, to answer the following question over the defendant’s objection: “Q. Mrs. 2 Hansen, why did you think that Mrs. Nichols was unable' to sleep much during the time you slept with her ?” The witness had already testified to the fact that the plaintiff did not sleep much or well. Thereafter her opinion as to the cause of such sleeplessness was wholly immaterial and incompetent. The question, in effect, required the witness to draw her conclusion from the facts and circumstances known to her, and concerning which she had already testified. Such question is improper, and the answer prejudicial error, because it invades the province of the jury, besides giving an opportunity to draw an erroneous conclusion, prompted by motives of friendly interest. Hamer v. Bank, 9 Utah 215, 33 Pac. 941; Saunders v. Southern Pac. Co., 15 Utah 334, 49 Pac. 646.
*247During the trial, Dr. Givens, a witness' for defendant, testified to the treatment plaintiff should have received after the accident, and which, in his opinion, would have promoted her recovery, and which course of treatment differed from that which plaintiff’s witnesses had testified she had in fact received. This evidence was evidently introduced for the purpose of showing the plaintiff’s present condition was not the result of defendant’s negligence, but caused or aggravated by plaintiff’s own subsequent want of care. Upon cross-examination, plaintiff’s counsel ashed the witness the following question, which was permitted to be answered ovér the defendant’s objection: “And if these conditions prevailed!, and those methods have all been applied, is it not possible that it might have been that these extreme conditions might have been caused directly by that nervous shock received in the collision and not have been the result of some inadvertent care?” This hypothetical question was objected to upon the ground that it included and assumed that all the things which the witness had testified as necessary to the proper treatment 3 of the plaintiff had been administered to her, when in fact a contrary state of facts had been shown by the testimony to exist. We think this objection should have been sustained. The hypothetical question thus submitted assumed facts which indisputably had neither been proven, nor in truth existed. Says the court in the case of Association v. Woodson, 12 C. C. A. 392, 64 Fed. 689: “It is a proposition too simple to require any citation of authorities that the material facts assumed in a hypothetical question must be proven on the trial, or, rather, that there must be evidence on the trial tending to prove them; otherwise it is error to allow them to he answered. How can we say that either the answers to the questions or the verdict of the jury would have been the same if the statements contained in the question, and not proved, had been omitted?” Had the question been in the negative, instead of the affirmative — as to whether the absence of this treatment would have affected plaintiff’s present condi*248tion — then the question would have been proper, and in line with the examination allowed by the court upon the part of defendant.
We see no other errors in the record, but, for the reasons above stated, we think the trial court should have granted a new trial. It is therefore ordered that the case be reversed, with costs, and that the cause be remanded to the lower court, with directions to grant a new trial.
BASKIN, J., concurs; BARTCH, J., concurs in result.