I dissent.
It is my considered opinion that the giving of the two improper instructions caused a miscarriage of justice and that the judgment should be reversed.
The ephemeral constitutional standard for identifying reversible error has not been rendered concrete by judicial effort. Certainly the people of California did not intend to nullify the right to a jury trial guaranteed by article I, section 7, of the California Constitution by adding article VI, section 4½, which requires a miscarriage of- justice to justify a reversal.* A proper construction would be consonant with the purpose of the amendment which is to relieve the judiciary of the burden of retrying cases merely because of technical errors. It does not license appellate courts to weigh evidence except where it is so massive on one side as to remove the issue from any doubt. The statement of this court in Herbert v. Lankershim, 9 Cal.2d 409 at 476 [71 P.2d 220], is pertinent: That article VI, section 4½ may dispel error only if the justice of the case preponderates so obviously that none of the errors could have contributed to the findings below.
To affirm this case because the errors committed were nonprejudicial, this court has been forced to make factual determinations from the record and effectively deprive appellant of his right to a jury trial. The majority has determined that the inference of negligence raised by the doctrine of res ipsa loquitur and by statutory violation is rebutted by defendant’s own testimony.
In Phillips v. Noble, ante, p. 163 [323 P.2d 385], the court instructed the jury that the happening of an accident does not necessarily mean there was negligence. In dissenting (p. 92) I suggested the following tests for determining prejudicial error:
(1) If there is a conflict in the evidence concerning defendant’s negligence and weak or nonexistent evidence of plain*627tiff’s contributory negligence, the giving of this instruction is prejudicial.
(2) If the evidence of defendant’s negligence is weak and there is substantial evidence of contributory negligence, the error is probably nonprejudicial.
(3) If plaintiff makes out a prima facie case based on res ipsa loquitur applied as a matter of law, it is always prejudicial error to give the questioned instruction.
This ease clearly falls within tests (1) and (3) above stated.
The Effect of the Instructions Upon the Jury
The trial court instructed the jury that if defendant violated the statutory duty to have proper brakes, then he was presumed negligent. The court previously gave the instruction that the occurrence of an accident does not necessarily imply negligence and the unavoidable accident instruction. Although res ipsa loquitur applies to this case as a matter of law, no instruction on this doctrine was requested.
The inference arising from defendant’s conduct forced him to produce evidence powerful enough to convince the jury that it was not probable that he was negligent. The effect of the instructions was to confuse or erase this impression in the jurors’ minds. (Butigan v. Yellow Cab Co., 49 Cal.2d 652 [320 P.2d 500] ; Jensen v. Minard, 44 Cal.2d 325 [282 P.2d 7].) This alone has been designated prejudicial error. (Davenport v. Stratton, 24 Cal.2d 232 [149 P.2d 4] ; Hyman v. Market Street Ry. Co., 41 Cal.App.2d 647 [107 P.2d 485] ; Scandalis v. Jenny, 132 Cal.App. 307 [22 P.2d 545].) The instruction in the instant ease is stronger than in Butigan because it omitted the cautionary statement that the defense of unavoidable accident may not be used by a defendant who did not use ordinary care. The addition of the instruction that a collision between two automobiles does not necessarily imply negligence made the error more damaging than was the case in Butigan.
These instructions probably confused the jury because:
(1) There could be no evidence of unavoidable accident in this case under the Butigan rule. A conscientious juror, reasonably expecting only pertinent instructions, would naturally search his memory for facts which might fit this pattern. The phrase “unavoidable accident” strongly suggests an undefinable area of activity between defendant’s nonnegligence and his slight negligence. In the instant case the evidence suggests defendant was not grossly negligent. Such negligence *628as the jury might have found could easily be swept under the carpet of unavoidable accident. Where the issue of negligence is a close one, such an alternative is tempting. The confusion caused by the unavoidability instructions was magnified here by the instruction that an accident of this character does not necessarily imply negligence.
(2) The inferences arising out of facts relating to this collision establish negligence on the part of defendant unless he proves otherwise. The jury must begin its reasoning from the side of plaintiff, not from a neutral position. These instructions tell the jury a contrary story and may effectively have eliminated the inferences from the minds of the jurors. To say they did not is to make a finding of fact by judicial prescience. To say it is not clear they did is to place on appellant the burden of showing they did. Just how any appellant is to prove the effect of these instructions upon each juror’s trend of thought is a mystery. But by deciding arbitrarily that an appellant must do so the court is taking away the right to trial by jury from appellants with justifiable complaint. This has been held prejudicial. (Russell v. Andersen, 101 Cal.App.2d 684, see 697 [226 P.2d 350] ; Bieser v. Davies, 119 Cal.App. 659, see 664 [7 P.2d 388].)
Because the inferences were obliterated by the instructions the jury did not have to examine defendant’s evidence. If the jury did not think the mere malfunctioning of brakes or defendant's sole control of the vehicle was sufficient evidence of his negligence, defendant needed no justification in their eyes. This court, however, has determined for them that defendant’s testimony was true and his actions reasonable even though the Constitution says the plaintiff may have this determined by a jury of his peers. The majority decision here is an excellent example of the mischief perpetrated by this court by taking upon itself the job of fact finding.
Dependant’s Testimony Does Not Explain the Failure op His Brakes
According to defendant’s own testimony:
(1) During the five months he owned the car its brakes always worked;
(2) He had his clutch repaired at Newton’s Garage two to four weeks before the collision. Defendant testified that the employees of the garage did not then recommend any repair of the brakes. There was no testimony that the brakes were even tested at that time!
*629(3) About two months before the collision defendant had his ear lubricated. The service station gave defendant a service receipt and guarantee which indicated by cheek marks that the wheel brake cables and master cylinder had been inspected and lubricated in accordance with the company’s lubrication guide. No service or replacement were recommended at that time.
All of this was self-interested testimony of defendant and it is open to suspicion for that reason. No inference can be drawn from number (2) as to the condition of the brakes at that time. The value of testimony under (3) is open to these questions:
(a) How thorough was the station’s inspection?
(b) How qualified were the personnel to judge the condition of the whole brake system ?
(c) Did defendant inspect the brakes when he bought the used car? Were his later inspections frequent and thorough enough ?
(d) Assuming the master cylinder and cables were in good condition, was the whole system tested? What part of it failed and caused the collision?
The latter is a vital point. The theory of res ipsa loquitur is that the defendant must show what caused the injury because only he knows. In this ease defendant did not present this evidence. It was incumbent upon him to show his lack of negligence in respect to the very cause of the accident if he was able to do so. (Dierman v. Providence Hospital, 31 Cal.2d 290 [188 P.2d 12].) He made no effort to do so nor to explain why he didn’t. His evidence is to be viewed with distrust (Code Civ. Proc., § 2061, subd. 7).
It is the jury’s function to determine the truthfulness of testimony and it may reject evidence it disbelieves. Therefore the fact that it was uncontradicted does not mean it would have to be believed. It is also a jury function to determine whether particular acts constitute negligence by applying the reasonable man test. The processes of a court are legal, not mechanical. In this case the majority has usurped all of those functions and determined facts from the record. Article VI, section 4½, and article I, section 7, do not permit us this privilege.
I would therefore reverse the judgment.
I have discussed this at length in two dissents: Buckley v. Chadwick, 45 Cal.2d 183 at 208 [288 P.2d 12, 289 P.2d 242], and People v. Tarantino, 45 Cal.2d 590 at 604 [290 P.2d 505].