the
offense of carnal knowledge, under RCW 9.79.020, and were found guilty by a jury. On appeal, they allege several errors in the proceedings. For the most part, the allegations are lacking in any merit and do not warrant discussion, but *414one of the contentions has such a substantial basis that a new trial must be ordered.
In this assignment of error, the appellants contend that the court erred in not granting a mistrial, which was requested by the appellants after the following incident had transpired:
The respondent put on the stand as its witness a doctor who had examined the complaining witness on the night following the attacks which she alleged had been made upon her by the appellants. The doctor testified that he did not find any pelvic abnormality or any visible foreign substance. He further testified that he took a vaginal smear and left it, together with a routine laboratory slip upon which the slide was identified, to be taken to the laboratory by a nurse. The doctor later received a report on the slide, he said. He had no knowledge of the number of people who had handled the slide after he put it aside for the nurse.
The laboratory technician was then called, and after his qualifications were established, he described the procedure for determining the presence of spermatozoa, and testified that he had performed such a test in response to a requisition from the doctor who had earlier testified. He was then asked what notation he made after the test, but the objection of the appellants was sustained. Although the court ruled that the witness could not testify further concerning the results of his test until the slide was properly identified, it refused to grant the appellants’ motion for a mistrial.
The respondent did not call the nurse who was supposed to have taken the slide, made out the requisition for the analysis, and presented it to the laboratory technician. No further evidence was offered to identify the slide on which he made his report.
It is the contention of the appellants that, at this point, the jury had received a clear impression that spermatozoa were found in the vaginal smear, although there was no direct testimony that such was the case, and we think this can hardly be gainsaid. Undoubtedly the jury must have reasoned that the answer of the technician, had he been allowed to testify, would have been that spermatozoa were *415found, as the state surely would not have called the witness if this were not the expected answer. It is also unlikely that they would doubt that the slide was the one submitted by the doctor who examined the complaining witness.
Since the slide which was examined by the laboratory technician contained no identifying marks and was handled by at least one other person before he received it, a person who was not present to identify the slide and was not available for cross-examination, the court properly refused to allow testimony as to the results of the test. See San Juan Cy. v. Hage, 54 Wn. (2d) 419, 341 P. (2d) 872.
However, the court was not obliged to declare a mistrial at that point, since the respondent was entitled to an opportunity to produce the witness or witnesses who could complete the identification. When it failed to do so, however, we think a mistrial should have been granted, for this reason: The evidence was in considerable conflict, and the jury could well have found the uncorroborated testimony of the complaining witness implausible. It could well have been that the inference which the jury most probably drew from the testimony of the laboratory technician was the determining factor which convinced it of the guilt of the appellants.
If it were reasonable to suppose that an instruction to disregard this testimony would have removed its effect from the minds of the jury, the appellants, having failed to request such an instruction, would be foreclosed at this point. But we think the impression created by this evidence was ineradicable from the minds of reasonable men. So compelling was the inference which it called forth that the members of this court find it difficult, if not impossible, to disregard it. We must conclude that an instruction, no matter how framed, could not have prevented the mischief. In such a case, a new trial is the only adequate remedy. A similar question was thus determined in State v. Albutt, 99 Wash. 253, 169 Pac. 584.
We have no doubt but that the prosecutor acted in good faith in presenting this witness and that he was taken by surprise when it developed that the laboratory technician *416was unable to identify the slide. But a holding that no prejudice to the appellants resulted from the introduction of his testimony might well encourage another to think that this is a convenient device for implanting a conviction in the minds of the jurors without the necessity of producing legally sufficient evidence. We do not, however, decide the appeal in favor of the appellants simply to discourage the use of such a device, but because we are convinced that a fair trial was impossible, once the testimony had been admitted, in view of the fact that the slide was never identified.
The judgment is reversed and the cause remanded for a new trial.
Finley, C. J., Donworth, Weaver, and Hunter, JJ., concur.