Opinion by
Hoffman, J.,Appellant contends that the trial judge committed reversible error when in reviewing the evidence he stated that appellant failed to call her husband in support of her alibi.
Appellant was charged with illegal sale of narcotic drugs. Appellant took the stand and testified that her husband and several other persons were with her in Allentown on the date of the alleged sale. None of these witnesses was ever called to testify in support of appellant’s alleged alibi. In reviewing the evidence, the trial judge stated: “The Commonwealth says . . . that these records do not establish an air-tight alibi and points out not one person was called to testify that the defendant was in Allentown that night — not her husband, not her friend, ...” (Emphasis added).
Generally, if a defendant raises an alibi and testifies as to the existence of named alibi witnesses, and if these witnesses are not called, it is permissible for the jury to draw the inference that the testimony of such witnesses would be adverse to the defendant. Commonwealth v. Wright, 444 Pa. 536, 282 A. 2d 323 (1971). If the uncalled witness is the spouse of the defendant, however, the inference is not permitted, Commonwealth v. Moore, 453 Pa. 302, 309 A. 2d 569 (1973), because the eviden-tiary inference is in conflict with the common law and the 'Pennsylvania statutory rule on incompetency of spouses to testify against each other in a criminal trial. Act of May 23, 1887, P.L. 158, §2(b), as amended, 19 *166P.S. §683. “It is clear the purpose of the statute is to bar, either husband or wife, from testifying against the other, and this is a rule which is not waivable by the parties. If the inference is allowed to operate, the whole purpose and effect of the statute would be negated. The statute by its very terms stops either spouse from adversely affecting a criminal case against the other; ... If the inference is allowed to operate, the very fact the spouse is not called adversely affects the other spouse.” Commonwealth v. Moore, supra, at 307 (footnote omitted).
The Commonwealth argues that no error was committed because the trial judge merely mentioned appellant’s failure to call her husband as a witness and did not instruct the jury as to any adverse inference that could be drawn. Comment on the failure of a defendant to call a spouse as a witness, however, also operates to negate the statutory purpose, since the judge invited the jury to draw an impermissible inference.
The lower court’s comment was not harmless beyond a reasonable doubt. Chapman v. California, 386 U.S. 18 (1967). Although the trial judge did not instruct the jury that they could draw an adverse inference from appellant’s failure to call her husband, the statement did go to the heart of the appellant’s alibi defense. The Commonwealth’s evidence consisted wholly of identification testimony of a police officer. While the officer had seen the appellant on previous occasions, the identification on the night in question took place in a cocktail lounge after dark. Thus, the jury had to decide whether the Commonwealth’s witness was more or less credible than the appellant. Because the trial judge’s comment damaged the appellant’s credibility, it cannot be declared harmless error.
Judgment of sentence reversed.