The declaration as amended was in four counts. The third count was a statutory count for the death of the plaintiff’s intestate “by reason of the negligence and carelessness of the defendant and the unfitness and gross carelessness of its agents and servants while engaged in its business ”; and the fourth count was at common law for conscious suffering caused by the negligence and carelessness of the defendant and its agents and servants. The plaintiff put in his case and rested. When he rested the counsel for the plaintiff stated to the presiding judge that he relied on the third and fourth counts only and that he waived the first and second. In reply to a question by the judge the plaintiff conceded that up to that point there was *19no evidence of the unfitness of the servants and agents of the defendant. Thereupon the defendant rested as to the gross negligence and carelessness of the defendant’s agents and servants as alleged in the statutory count. The judge then ruled that there was no evidence of the gross negligence or carelessness, or of the unfitness of the defendant’s servants and agents, and declined to submit the case to the jury on those issues and limited the plaintiff under the third count to the questions of the negligence of the corporation itself. The plaintiff duly excepted, and the first question relates to the correctness of the rulings thus made.
The plaintiff relies on the doctrine of res ipso loquitur, as applied to the circumstances of this case, to show that there was evidence warranting a finding that the accident was due to gross negligence on the part of the defendant’s servants and agents. An accident may no doubt happen under circumstances which, in the absence of any explanation, without anything more, would warrant a finding that it could not have occurred except for gross negligence and carelessness on the part of the defendant’s servants or agents. See McNamara v. Boston & Maine Railroad, 202 Mass. 491. But negligence to be gross must include an element of carelessness so great that the court or jury can say that there was not only an absence of the due care that should have been exercised, but also a degree of negligence materially greater than that which would constitute ordinary negligence. No doubt what would be gross negligence under one set of circumstances might not be so under another; and no doubt, also, the highly dangerous consequences to be apprehended in one case might contribute to render that gross negligence which would not be such in another case.
In the present case the plaintiff introduced no independent evidence to show that there was anything defective or improper in the construction or operation of the car. On the contrary the uncontradicted testimony of the plaintiff’s witnesses was that, down to the instant of the explosion, the car had been running smoothly and that it had stopped and started in the ordinary way, and that there had been nothing unusual about it. Under such circumstances it cannot be said that the explosion of itself furnished evidence of such conduct on the part of the de*20fendimt’s servants and. agents as to constitute gross negligence. The plaintiff has not argued that there was any evidence of the unfitness of the defendant’s servants or agents. We think that the rulings excepted to were correct.
The plaintiff also excepted to certain rulings in regard to matters of evidence. The defendant called as a witness one Campbell, who testified that he was foreman of the electrical equipment of the defendant during a period which covered the time of the accident; and after stating what his duties were he went on to describe the construction and operation of the cars used by the defendant. He also testified that he examined the car in question on the night of the accident, and after describing certain tests that he made in regard to the controller and the result of them, he was permitted to answer without objection that the conclusion to which they led him was that the controller was “ O. K.” He further testified as to the condition in which he found other parts of the mechanism, and what he did in the way of causing repairs to be made. On cross-examination the plaintiff sought to use him as an expert, and for that purpose, after the witness had testified that the insulation was scorched on some of the wires, asked him, assuming that the insulation was worn off, what effect that would have upon the use and operation of the controller. This was objected to and excluded on the ground that the witness had not been put on as an expert. After some further questions and answers in regard to the principles and operation and results in certain cases of electric power, which were evidently put to bring out the knowledge of the witness in regard to such matters the witness was asked, “ How from your study of this case and from your familiarity with the principle of the resistance box did you form any opinion as to when that was burned out, or blown out ? ” And again, “ Did you form an opinion as to what was the cause of the' burning of the panel?” Upon objection both questions were excluded,' the presiding judge stating in substance, "later, that anything in the nature of facts could be shown by the witness, but anything in the nature of an opinion was excluded.
It is no doubt true, as contended by the plaintiff, that while the general rule is that the question whether a witness is quali*21fled as an expert is for the trial court, nevertheless, when the facts upon which the decision of the question depends are undisputed, the question becomes one of law, and the decision of the trial court may be reviewed. Muskeget Island Club v. Nantucket, 185 Mass. 303. It is also no doubt true that the fact that a witness is not offered as an expert by the party calling him will not prevent the other side from using him as such if it turns out that he has the necessary qualifications. In the present case, while the witness showed great practical familiarity with the equipment and operation of electric cars, and might well have been allowed to express his opinion, we do not think that the facts in regard to his qualifications were so clear and undisputed that it can be said as matter of law that the presiding judge was wrong in excluding the questions which it did.
We do not understand that any ruling was asked for or any exception saved in regard to the' witness’s testimony at the former trial.
Exceptions overruled.