(with whom Wilkins, J., joins, dissenting). In my view the defendant was fairly tried, and his conviction should be affirmed. I therefore dissent.
In Commonwealth v. A Juvenile, 365 Mass. 421, 426 (1974), we held that "if a defendant agrees in advance to the admission of the results of a polygraph test regardless of their outcome, the trial judge, after a close and searching inquiry into the qualifications of the examiner, the fitness of the defendant for such examination, and the methods utilized in conducting the tests, may, in the proper exercise of his discretion, admit the results, not as *466binding or conclusive evidence, but to be considered with all other evidence as to innocence or guilt.”
Pursuant to that holding, the defendant moved that the Superior Court allow him to take a polygraph examination at the expense of the Commonwealth "for the purpose of introducing its results into evidence at this trial.” The defendant personally signed an agreement "to allow the results of his polygraph examination to be admitted into evidence even if the results are unfavorable to him,” and a waiver of "his right against self-incrimination.” The judge allowed the motion, and there is no contention that he did not make the required "close and searching inquiry.”
The defendant took the examination, and the results were unfavorable to him. Relying on our decision, the prosecutor offered the results in evidence, the judge exercised his discretion to admit them, and the jury found the defendant guilty. Now the court holds that we did not mean what we said, and that the defendant should be relieved of his agreement, largely on the basis of considerations advanced in the dissenting opinions in Commonwealth v. A Juvenile, supra.
My disagreement is on a narrow ground. I fully agree that there are often difficulties with the reliability of polygraphic evidence, as indeed there are with many of the types of evidence on which we customarily rely. If the trial judge had excluded the evidence, there would of course have been no appellate review, whatever the outcome of the trial. Likewise, if he had limited the evidence to impeachment of the defendant’s testimony, as the defendant requested, there would be no reversible error. But the judge did neither. In my view we act unwisely when we substitute our judgment for his on a matter that he understood far better than we can. Even more unwise is the substitution of an arbitrary rule for the exercise of sound judgment, particularly when the arbitrary rule rests on factual considerations of dubious standing, deduced from selected fragments of the highly controversial *467literature on the subject, unsupported by anything in the record.
Particularly troublesome is the implicit suggestion that the defendant, as matter of right, must be relieved of his agreement because the "limited probative value” of the evidence is outweighed by "confusion and prejudice of the jury; intrusion into jury function; and use of trial resources.” The evidence in question is evidence of the pretrial words, conduct, and condition of the defendant, relevant to his guilt. Such evidence is traditionally admissible against him on the issue of guilt or innocence, once he has waived his privilege not to be a witness against himself. It is not ordinarily the function of an appellate court to balance the probative value of the defendant’s relevant admissions against possibilities of confusion and the like in deciding whether evidence of the admissions is admissible. Such balancing on appeal is not only likely to produce confusion and uncertainty; it invades the province of the jury and the trial judge.