opinion: MAGENAU, ADMINISTRATOR, v. AETNA FREIGHT LINES, INC.
  No. 439.
  Argued May 18, 1959.—
  Decided June 15, 1959.
  Harry L. Shniderman argued the cause for petitioner. With him on the brief were M. Fletcher Gornall, Jr. and William W. Knox.
  William F. Illig argued the cause for respondent.'. With him on the brief was' John E. Britton.
  Mr. Justice Clark
  delivered the opinion of the Court.
  This is a diversity case for wrongful death of petitioner’s decedent, who was killed when a tractor-trailer leased by respondent crashed off a Pennsylvania highway. The action was tried to a jury on a negligence theory and judgment went for petitioner. 161 F. Supp. 875. The Court of Appeals reversed, finding that under Pennsylvania law the decedent was an employee of respondent and that the Pennsylvania Workmen’s Compensation Act, Purdon’s Pa. Stat. Ann., 1952, Tit. 77, provided the exclusive remedy. 257 F. 2d 445. We granted certiorari, 358 U. S. 927, on the question whether, in the light of Byrd v. Blue Ridge Rural Electric Cooperative, Inc., 356 U. S. 525 (1958) (decided after this case was argued, in the Court of Appeals), the matter of the relationship of the decedent to respondent was a jury question. We have concluded that Byrd does control that issue and that the judgment must therefore be reversed.
  Respondent is an interstate motor carrier of freight certificated under the Interstate Commerce Act. It had leased a tractor-trailer, complete with driver,, from one Fidler, an' independent contractor. Its lease contract, which had been in effect for four years, required Fidler to furnish the driver as well as to keep the leased equipment in repair. In this connection the evidence indicates that Fidler had authorized his driver, where circumstances required, to hire services and purchase necessities on trips of this kind. • The vehicle and driver leased by respondent were en route from Syracuse, N. Y., to Midland, Pa., with 36,000 pounds of steel'when the mishap leading to decedent’s death occurred! The trip from. Syracuse had been so beset with difficulties, such as tire replacements, battery trouble and brake failure, as well as bad weather, that it had already consumed 7 days’ time. Under ordinary conditions 20 hours .of elapsed time would have been sufficient. During a stop at a tavern near Waterford, Pa., the driver, Schroyer, was talking to the tavern keeper about his truck troubles when decedent and his cousin entered the place. Schroyer offeréd the cousin $25 to accompany him for the remainder of the trip and, upon, refusal, made the same offer to decedent. .The latter accepted.. While the evidence is weak on the point, the indications are that decedent’s job was to aid the driver in the event further trouble with the truck was encountered. Decedent was experienced with cars and had worked for a short time as a mechanic. Schroyer and decedent proceeded in the truck-trailer toward their destination, with the former driving. Some hours later the vehicle was found off the road on the downside of an embankment. Both men were dead.
  This action ensued, in which petitioner alleged neglir gence on the part of Fidler and respondent for continuing to operate the vehicle with knowledge. of its defective brakes. Liability, of respondent was rested upon the rule that its status as a certificated carrier made it liable for the negligence of Fidler, its independent contractor, whose motor equipment was operated under the former’s I. C. C. certificate. ■ This is the law of Pennsylvania, Kissell v. Motor Age Transit Lines, 357 Pa. 204, 209, 53 A. 2d 593, 597. Petitioner’s theory was that his decedent was an invitee on the tractor-trailer, and that Fidler and his driver, Schroyer, therefore, owed decedent a duty of due care for breach of which respondent was liable under its I. C. C. certificate. Respondent claiméd that decedent was a trespasser and, under Pennsylvania law, that it was therefore liable only for wanton misconduct. After discovery had been exhausted, respondent moved for summary judgment on the ground that the circumstances of decedent’s engagement by Schroyer created an employer-employee relationship between, it and decedent under the State workmen’s compensation statute. The motion was denied and the case went to trial. It was submitted to the jury on special interrogatories covering the issues as to liability and a general charge as to the damages. The trial judge entered judgment on the special issues and the damage verdict for $76,500.
  Interrogatory No. I, the meaning of which is now in controversy, inquired as to whether it was “reasonably necessary for the protection of defendant’s [respondent’s] interests” to engage decedent. The Court of Appeals held that the affirmative answer of the jury classified decedent as respondent’s employee bringing him within the general definition of § 104 of the Pennsylvania Workmen’s Compensation Act. It' noted that respondent had conceded that decedent was its “casual” employee but that this was not enough to take him out of the Act’s coverage for, in addition, such casual employment must ■“not be in the regular course of business” of respondent. This, the Court of Appeals said, was a question of law under Pennsylvania practice and open to review. It held that the finding under Interrogatory No. 1 put decedent “into the regular business” of respondent. This holding would call for the dismissal of this suit, as petitioner’s exclusive remedy would be under the Pennsylvania Workmen’s Compensation Act.
  Since the keystone of the Court of Appeals’ holding depends on its interpretation of Special Interrogatory No. 1, we note the views of the trial judge on that issue. In his opinion on the motion of respondent for judgment non obstante verdicto, he observed that “the interrogatory . . . was not. so phrased as to require the jury to determine whether decedent was an employe'e of Aetna.” Rather, it “was simply to secure a finding from the jury as to the reasonable necessity of Schroyer engaging decedent.’’ 161 F. Supp., at 878. Likewise during the trial, in a colloquy with counsel as to this interrogatory, he advised: “[Y]ou notice there I refrain from saying just what his [decedent’s] status is. I don’t think it necessary to have the jury find whether he was employed or not; I think that is a question for the law.” On balance we believe that an examination of the record supports this interpretation of Interrogatory No. 1, although it must be admitted that the apparently inadvertent use of the. words in “protection of the defendant’s interest” in the interrogatory may have been taken in a different light by the jury.
  Be this as it may, however, not only the question of the relationship of the decedent to respondent should have been submitted to the jury but, in order to meet § 104’s definition, it should likewise have passed upon whether the employment, if any, Was “casual” and not “in the regular course” of respondent’s business. Our opinion in Byrd came down subsequent to argument in the Court of Appeals. As we said in that case “An essential characteristic of [the federal system] is the manner in which, in civil common-law actions, it distributes trial functions between judge and jury . . . [assigning] the decisions of disputed questions of fact to the jury.” Byrd v. Blue Ridge Rural Electric Coop., supra, at 537. We found there that the South Carolina rule in compensation cases, permitting courts to decide such factual issues without the aid of juries, was not “announced as an integral part of the special relationship, created by the statute.” Id., at 536. We held that under such circumstances “the federal court should. not follow the state rule.” Id., at 538. The same reasoning applies here. We have been given no reason for the distinction in the Pennsylvania practice of trying ¡Aich disputed factual issues to the court. Respondent does not claim that the rule is an “integral part of the special relationship” created by its statute but rather that the disputed issue of employment was in fact submitted to the jury. It cannot be gainsaid that all of the disputed issues' were not so submitted. In order to determine whether the Pennsylvania Act bars recovery here the court must have a full answer as to the status of the decedent as an employee under § 104 of the Act. If the jury, under proper instructions, finds facts which show that, under § 104, the decedent was respondent’s employee and that such employment Was “casual” and not “in the regular course” of respondent’s business, then it can find for petitioner.
  We are therefore of the opinion that a new trial, on the. whole case is necessary, since these-disputed issues are so interrelated with the ultimate issues of liability and damages that a limited hearing would not be in the interest of fairness and efficiency in judicial administration. If the evidence on that trial is such as to justify with reason different conclusions on the factual issues as to the relationship of decedent as an employee, under § 104 of Pennsylvania’s Act, of either respondent or its contractor, Fidler, resolution of those issues, along with others that arise from'the evidence; will be for the jury. The jury’s verdict at that trial will determine if as well as in what amount petitioner may recover in this action.
  Reversed and remanded.
  Also see 49 Stat. 557, as amended, 49 U. S. C. § 315, which provides that a certificate holder must carry insurance to satisfy any final judgment for injuries due to the “negligent . . . use of motor véhicles under such certificate.”
  “Interrogatory Number 1. Under the evidence in this case, do you find that an unforeseen contingency arose which made it reasonably necessary for the protection of the defendant’s interests that the driver Charles Schroyer engage the decedent Norman Ormsbee, Jr. to accompanying him for the remainder of the trip?”
  Section 104 of the Pennsylvania Workmen’s Compensation Act, Purdon’s Pa. Stat. Ann., 1952, Tit. 77, § 22, Cum. Supp., provides:
  “The term ‘employe,’ as used in this act is declared to be synonymous with servant, and includes—
  “All natural persons who perform services for another for a valuable consideration, exclusive of persons whose employment is casual in character and not in the regular course of the business of the employer, and exclusive of persons to whom articles or materials are given out to be made up, cleaned, washed, altered, ornamented, finished, or repaired, or adapted for sale in the worker’s own home, or on other premises, not under the control or management of the employer. Every executive officer of a corporation elected or appointed in accordance with the charter and by-laws of the corporation, except elected officers of the Commonwealth or any of its political subdivisions, shall be an employe of- the corporation.”-