The plaintiff was injured by the negligence of the defendant Tweedy in the operation of an automobile which was owned by the named defendant, and from the refusal of the trial court to set aside a verdict in his favor and from the judgment on that verdict she has appealed, claiming in the latter appeal errors in the charge. The complaint alleged that she was liable upon the basis of the family car doctrine; but the case was tried and has been presented to us on the broader ground of a presumption of agency growing out of the fact that she was the owner of the car. We shall follow the theory adopted by the parties and determine the issues on the latter ground. Conn. App. Proc., 22. The basic question involved is the effect of the presumption created by 1661c of the Cumulative Supplement of 1935, which is printed in the footnote.1 The language of this statute is quite similar to that of 1658c of the Cumulative Supplement of 1935, which provided that proof that the operator of a motor vehicle is related to the owner in certain specified degrees shall raise a presumption that the car is being operated as a family car and shall impose upon the defendant the burden of rebutting the presumption; and we have treated the two as having like effect. Both go further than merely establishing a presumption in that they definitely place the burden of rebutting it upon the defendant. But that burden is restricted to rebutting the presumption; it does not shift to the defendant the burden of proving *Page 188 that the car was not a family car or that the operator was not the agent of the owner, as the case may be. The presumption ceases to be operative when the trier finds proven facts which fairly put in issue the question, and the burden of proving that the car was a family car or was operated by an agent of the owner, as the case may be, then rests upon the plaintiff; if no evidence relevant to the issue is produced, or, if countervailing evidence is produced but the trier does not believe it, the presumption applies, and the plaintiff is entitled to have the issue found in his favor. O'Dea v. Amodeo, 118 Conn. 58, 64, 170 A. 486; Leitzes v. F. L. Caulkins Auto Co., 123 Conn. 459, 462,196 A. 145; Lockwood v. Helfant, 126 Conn. 584, 587,13 A.2d 136. These statutes do not go so far as does 1399e of the Supplement of 1939, which places upon the defendant the burden of pleading and proving contributory negligence, for, under the former, the burden is merely to rebut the presumption. On the other hand, because they do place that burden upon the defendant, they go further than the common-law presumption adopted in many states that one operating a car owned by another is presumed to be his agent acting within the scope of his employment, which has been held to be overcome when substantial countervailing evidence is produced. Potts v. Pardee,220 N.Y. 431, 433, 116 N.E. 78; McIver v. Schwartz,50 R.I. 68, 70, 145 A. 101; Echols v. Hurt,116 Okla. 43, 45, 243 P. 493; and see O'Dea v. Amodeo, supra, 63.
The statute before us does not establish that the operator of the car is an agent of the owner, acting within the scope of his employment, but only creates a presumption capable of rebuttal. We cannot hold that there is such a lack of rational connection between the fact of operation by a person to whom the *Page 189 statute applies and the facts to be presumed as to make it arbitrary or unreasonable. The legislature might reasonably have considered that in the great majority of cases the operator of a car owned by another is his agent acting within the scope of his employment, that the facts are usually peculiarly within the knowledge of the defendant and that it is peculiarly within his power to produce evidence as to them. Kolensky v. DeFrancesco, 102 Conn. 660, 662, 129 A. 777. It is a commentary upon the reasonableness of the statute that, as we have noted already, many courts, without the benefit of any statute, have applied a similar presumption; see, in addition to the cases previously cited, Gehloff v. Kandler, 204 Wis. 464, 466,234 N.W. 717; Ferris v. Sterling, 214 N.Y. 249, 253,108 N.E. 406; Crowell v. Padolsky, 98 N.J.L. 552, 120 A. 23; Birch v. Abercrombie, 74 Wash. 486, 489,133 P. 1020; 9 Blashfield, Cyclopedia of Automobile Law, 6065. The statute falls within the decisions of Mobile, J. K. C. R. R. v. Turnipseed, 219 U.S. 35,43, 31 Sup. Ct. 136, and Atlantic Coast Line v. Ford,287 U.S. 502, 53 Sup. Ct. 249, rather than, as claimed by the defendant, within that of Western Atlantic R. Co. v. Henderson, 279 U.S. 639, 49 Sup. Ct. 445. The statute is not invalid on constitutional grounds.
The defendant does not, in her brief, urge any specific objections to the charge, which followed the decisions of this court to which we have referred, and there is no occasion to consider further the appeal from the judgment. We are handicapped in our consideration of the ruling refusing to set the verdict aside because, by agreement of counsel, all testimony offered by the plaintiff was deleted from the transcript before it was printed for the record except a statement made out of court by the defendant's son, offered to contradict certain testimony given in court. There seems to be no *Page 190 dispute as to the following facts: The plaintiff, a pedestrian, at about 1 o'clock on a Sunday morning was injured because of the negligent operation of the car in question by the defendant Tweedy. The car was owned by the named defendant, whose home is in New Jersey, where it was registered in her name. Her son Donald was a student at Yale, and the car was kept by him at the university. Tweedy lived in the same dormitory as Donald Gregg. Another young man who lived in the same dormitory was a passenger in the car.
The only evidence as to the circumstances under which Tweedy came to be in possession of the car was apparently offered by the defendants. Tweedy and Gregg testified that on the night of the accident the former borrowed the car, paying $1 for its use in accordance with a custom among the students. Tweedy testified that his purpose was to go on a party to which he had been invited and Gregg testified that Tweedy made the situation seem urgent enough so he loaned the car. Both testified that Tweedy had never before borrowed it. Gregg testified that he had to some extent loaned the car at other times. Both he and his mother were questioned as to the purposes for which he was keeping the car in New Haven, as to any instructions she had given him in regard to loaning it and as to her knowledge of his loaning it to others, and in the testimony of these witnesses in regard to these matters there are certain inconsistencies and contradictions; but both agreed that in general the use of the car was left to Gregg's judgment and discretion. Mrs. Gregg testified that she had no knowledge that the car was loaned to Tweedy until informed later of the accident, that she could not recall whether her son telephoned her about the accident on the Sunday on which it occurred and that in using it Tweedy was not *Page 191 on any errand for her or doing anything for her benefit; and it is implicit in her testimony that she was not in New Haven on the night when the car was borrowed.
Ordinarily it is the exclusive function of a jury to determine whether they will believe or disbelieve the testimony of witnesses, and, however mistaken a court may think they are, it cannot override their conclusion; Conn. App. Proc., 113, 114; and this rule applies under statutes like the one before us, as regards a conclusion by a jury that facts sufficient to rebut the presumption have been proved. O'Dea v. Amodeo, supra, 67; Lockwood v. Helfant, supra, 587. But that conclusion may be so unreasonable that it will constitute an error in law, and where such a situation exists it is the duty of the court to interfere. Roma v. Thames River Specialties Co., 90 Conn. 18, 20,96 A. 169; Baril v. New York, N. H. H.R. Co., 90 Conn. 74,76, 96 A. 164; Dudas v. Ward Baking Co.,104 Conn. 516, 518, 133 A. 591; Levy v. Bromberg,108 Conn. 202, 204, 142 A. 836. It may be that in this case the jury could properly have disregarded all the testimony which tended to limit Gregg in the use or loaning of the car, leaving the situation as one where the borrowing of it could not be found to be without the implied consent of Mrs. Gregg. But consent on her part to its use by Tweedy would not in itself determine the question of her liability for his negligence, for that would depend upon the fact that in using it he was doing something in the execution of her business. Adomaitis v. Hopkins, 95 Conn. 239, 241,111 A. 178; Mastrilli v. Herz, 100 Conn. 702, 704,124 A. 835; Turoff v. Burch, 60 App. D.C. 221,50 F.2d 986; 5 Blashfield, op. cit., 3005, 3023. It would not be enough to establish Mrs. Gregg's liability that she left the use of the car while it was in New Haven to *Page 192 the discretion of her son and knew that he at times loaned it to others; or even that she might be pleased to have him do so because it might give him a better standing among his fellow students; the law does not, in determining agency, take account of indefinite considerations and possible motives of such a nature. Whiteman v. Al's Tire Service Garage, Inc.,115 Conn. 379, 382, 161 A. 519. In this case the jury could not reasonably reach any other conclusion than that Mrs. Gregg was not in New Haven on the night the car was borrowed, that, with that as a basis, she did not know that Tweedy had borrowed it, and that, in using it, he was not doing anything in her behalf. With these facts in the case, the presumption would be rebutted; and, as the record discloses no evidence sufficient affirmatively to prove that Tweedy, in using her car, was her agent acting within the scope of his authority, a verdict could not properly be rendered against her. The trial court should have set the verdict aside.
There is error, the judgment is set aside and a new trial is ordered.
In this opinion JENNINGS, ELLS and DICKENSON, Js., concurred.