This is an appeal pursuant to G. L. c. 278, § 33B, following a Superior Court jury verdict that the appellant, a juvenile, is a delinquent by reason of manslaughter. The facts are essentially those recited in our previous decision in this case.1
*423Six grounds for reversal were argued. We will deal first with the issues surrounding the trial judge’s denial of the juvenile’s pre-trial motions for the admission of polygraph, or “lie detector” test results. From the record it is clear that substantial advances have been made in the field of polygraphy since we rejected the admission of such evidence in Commonwealth v. Fatalo, 346 Mass. 266 (1963).
I.
In a written motion to the trial court, the juvenile stated that on May 26, 1970, a polygraph examination was administered to him by two polygraph experts of his own choosing, and that the results indicated that he was telling the truth when he denied having caused, directly or indirectly, the death of the victim in this case. He wished to “offer testimony of qualified experts at trial to demonstrate the scientific reliability of the polygraph, the scientific acceptability of the polygraph with particular attention to the increased acceptability of the polygraph since 1963 when its admissibility was last ruled on by the Supreme Judicial Court... Commonwealth v. Fatalo, 346 Mass. 266, the manner in which the test was administered to the defendant, the physiological, psychological, and technological manner in which the test is effective, and the opinion of the test examiners and the specific basis for the opinion, regarding the truthfulness of defendant’s answers to questions which are extremely relevant to the case in that they relate to the substance of the crime alleged by the complaint against the defendant.” Attached to the motion were three memorandum opinions by trial courts, two Federal and one State, allowing polygraph results in evidence in criminal cases. United States v. Ridling, 350 F. Supp. 90 (E. D. Mich. 1972). United States v. Zeiger, 350 F. Supp. 685 (D. D. C. 1972), revd. 475 F. 2d 1280 (D. C. Cir. 1972). People v. Cutler (Superior Ct. of Cal. for L. A. County, November 6, 1972) (unreported).
*424The trial judge conducted a preliminary hearing at which the juvenile introduced the expert testimony described in his written motion. At the conclusion of the hearing, the juvenile made a supplemental oral motion requesting that the court order an additional polygraph examination by a court appointed examiner, whose results would be admissible together with or independent of those of the juvenile’s expert, or that the Commonwealth be ordered to conduct an examination by an expert of its own choosing, and have those results admissible together with those of the juvenile’s expert.
The trial judge denied the juvenile’s motions, with expressed reluctance. He said, “Polygraphic tests are now generally and widely accepted in thé scientific community. The machine has proven to be a reliable instrument for detecting deception. Since the year 1963, polygraphic testing has become more reliable, and scientific acceptance thereof has increased. Advances have been made both to the machine itself and in the ways of administering the test. When conducted by competent polygraph examiners under proper examination conditions, polygraphic testing possesses a high degree of reliability and scientific acceptability. [The] polygraphic test of the juvenile was conducted by a qualified and highly competent polygraph examiner. Notwithstanding the foregoing findings and though counsel has cited some instances where the results of polygraphic tests have been admitted into evidence, I am not convinced that the courts in general have given widespread acceptance to this type of evidence, nor is there any indication that state legislatures have passed legislation permitting such tests or the results thereof as evidence. In any event, I do not feel that a favorable determination of the admissibility, if indeed it is warranted, should be made in the first instance by the trial judge. If any change in this direction is at all indicated, then it is a matter that is better left to an appellate court, particularly where our Supreme Judicial Court has already expressed its views regarding the acceptability of this type of evidence .... In conclusion, *425the written motion and the supplemental oral motion . . . [are] denied.”
It is evident that the judge was convinced of the polygraph’s reliability and evidentiary value but felt that as a trial judge he should wait for our prior approval before admitting such evidence. In Commonwealth v. Fatalo, supra, we held that the results of polygraph tests were not admissible as evidence in a criminal case because the test had not yet achieved general acceptance by the scientific community as a reliable method for determining whether an individual is telling the truth. While not establishing universal scientific approval of a demonstration of infallibility as prerequisites to admissibility of polygraph test results, we felt that the results could not be admitted until the “substantial doubts which presently revolve about the polygraph test” were resolved. 346 Mass, at 270. The juvenile, in attacking the validity of the trial judge’s denial of his motions, asserts that developments in the field of polygraph testing since the Fatalo case and the recent acceptance of polygraph results as evidence by a few trial courts, demonstrate that the doubts which troubled us in 1963 can no longer be called substantial enough to deny admissibility to the results of tests conducted on a criminal defendant by experts under proper conditions. We do not accept that argument in full force. Although we acknowledge that these scientific and legal developments indicate that the polygraph is making progress in a hoped for evolution toward complete evidentiary recognition, we nevertheless are unwilling to say at this time that the standard in the Fatalo case has been met and that the polygraph test results should henceforth be subject to the same rules of evidence applicable to other forms of acceptable expert scientific evidence. We do, however, think that polygraph testing has advanced to the point where it could prove to be of significant value to the criminal trial process if its admissibility initially is limited to carefully defined circumstances designed to protect the proper and effective administration of criminal justice. Accordingly, we hold for *426reasons stated below 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 thé 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 binding or conclusive evidence, but to be considered with all other evidence as to innocence or guilt. As a prerequisite the judge would first make sure that the defendant’s constitutional rights are fully protected.
Engaging at this point in an exhaustive and lengthy treatment of the subject of polygraphy would to a large extent be but a rehash of what has already been effectively said elsewhere.2 We will instead, based mainly on the testimony before the trial judge, limit ourselves to a discussion of the polygraph and the associated scientific and legal problems to the extent it is necessary to explain the conclusions reached by us. The polygraph machine is a scientific device which through measurement and recording of involuntary bodily responses — blood pressure, pulse rate, respiration, and skin resistance to electricity — seeks to determine whether an individual is telling the truth. The fundamental assumptions of polygraphy are that (1) there is a regular relationship between lying and emotional states and (2) there is a regular relationship between these emotional states and measurable physiological changes in the body. See Skolnick, Scientific Theory and Scientific Evidence: An Analysis of Lie-Detection, 70 Yale L. J. 694, 700 (1961). In short, the polygraph machine is said to be capable of determining an individual’s subjective state of *427mind through analysis of objective criteria which cannot be manipulated by the individual.
Equal to the importance of the machine itself is the competence, experience, and education of the test examiner. “[I]t is the examiner who must screen out the ‘unfit’ examinee, conduct the important pre-test interview (which is essential to the proper preparation of the actual test questions), and supervise the environment of the test to eliminate possible distortive influences, as well as ask the questions and interpret the resulting polygrams.” United States v. DeBetham, 348 F. Supp. 1377, 1385 (S. D. Cal. 1972).3 Overall, the training and background of polygraph examiners have become more sophisticated in recent years, and the “practice has acquired the usually accepted indicia of a profession, such as a national professional organization, training schools, qualification standards, yearly seminars, and specialized publications.” United States v. Zei-ger, supra, at 688. Nevertheless, as a profession, polygraphy has yet to achieve a uniform minimum level of competence. As one court said, “[T]he polygraph, the theory, the technique and the hardware seem to have outstripped the general acceptance of polygraph personnel in development. Although the profession of polygraph experts is becoming standardized and professionalized, it has not yet developed adequate ways and means to police itself. Although the profession has adopted a code of ethics and machinery exists in the professional organization to discipline the unqualified and unethical, the chance of serious impropriety on the part of polygraph examiners must be considered.” United States v. Ridling, supra, at 96.
Notwithstanding the present inconsistencies in abilities to be found among examiners as a whole, increasing numbers of individuals are receiving the type of training necessary to prepare them for this role. Moreover, the equipment itself has undergone technical refinements. As *428these developments have coincided, polygraph testing has come to be regarded as reliable in a growing number of circles, governmental, scientific, legal and private.4 In what must be regarded as one of the leading studies on the question of polygraph reliability, the authors, who had earlier recommended against the use of polygraph results as evidence, concluded that while “[w]e profess no infallibility for the Polygraph technique ... we can sincerely report it to be a very reliable aid in the determination of truth or deception.” Reid and Inbau, Truth and Deception (preface) (1966). The percentage of known errors with the technique in the laboratories of John E. Reid and Associates is “less than 1 per cent. Of the remainder no diagnosis at all is attempted in about 5 per cent of the cases, because of such factors as the physiological or psychological impairment of the subjects.” Id. at 234. But since this and other similar studies5 were conducted under optimum conditions by highly sophisticated examiners, they cannot be seen as wholly accurate predictions of test results in general, where there are many variables involved, most notably in the sophistication of the examiners. Additionally, besides these essentially practical problems, there still remains in certain portions of the scientific community resistance to polygraphy’s basic assumptions as to the relationship between lying and certain emotional states, and the relationship of those emotional states to measurable physiological changes in the body. See Skolnick, supra; Heckel and others, Polygraphic Variations in Reactivity between Delusional, Non-Delusional, and Control Groups in a “Crime” Situation, 53 J. of Crim. L., Criminology and Police Science, 380 (1962). These assumptions are disproved to a certain extent by the undisputed fact that some persons *429can tell undetectable lies, e.g., pathological liars, emotionally unresponsive subjects who have rationalized their behavior, children with an active imagination unable to distinguish between reality and fantasy, and others. See Highleyman, The Deceptive Certainty of the “Lie Detector,” 10 Hastings L. J. 47 (1958). Floch, Limitations of the Lie Detector, 40 J. of Crim. L., Criminology and Police Science, 651 (1950).
In sum, despite very significant progress in recent years, the field of polygraphy is still challenged forcefully on theoretical grounds and has yet to achieve a predictable level of consistency among examiners. For these reasons we do not believe that at this time polygraph test results should be generally admissible in evidence in criminal trials. Commonwealth v. Fatalo, supra. Yet we cannot ignore completely the potential value of polygraph testing (when requested by the defendant as stated above) as an aid to determining whether an individual is telling the truth when conducted by an examiner found to be well qualified in all aspects of testing and in the screening of the subject.
We believe that the proper determination of reliability and competence of examiners can be achieved through close scrutiny by the trial judge of an examiner’s qualifications, and by requiring the defendant to agree in advance (with all proper safeguards) to the admissibility of the results of a polygraph test. Dealing first with the question of examiner qualification, we do not think it wise at this time to limit the trial judge’s discretion on matters of expert testimony by formulating strict minimum standards as prerequisites to qualification of polygraph experts,6’ but we wish to emphasize that in light of the crucial importance of the examiner’s ability in relation to the *430polygraph’s reliability, it is essential that the trial judge exercise a high degree of care in assessing an examiner’s credentials. Special attention should be given to an examiner’s experience, a factor which is at least as important as the amount and type of formal training. By way of illustration, we think that the expert offered by the defendant in this case is amply qualified,7 though we do not wish to be understood as saying that his credentials establish minimum standards for qualification. It is the combination of training, experience, and demonstrated ability that should be determinative.
Secondly, we believe that in view of the possibly damaging consequences of an agreement to admit the results of a yet to be taken polygraph examination, a defendant who has entered into such an agreement may be highly motivated to assure that the examiner is well qualified and that the test is conducted under proper conditions. Of course it is possible that in some cases a defendant might select an examiner with minimal qualifications on the assumption that he could be more easily discredited if the results are adverse to him. We think, however, that the trial judge’s power to rule on an examiner’s qualifications, especially in light of our expressed concern for demonstrated excellence, effectively minimizes such a possibility.
There are four situations within this framework for admissibility which we consider to come within the judge’s discretion: (1) where the defendant moves that he be allowed to submit to an examination conducted by an examiner of his own choosing; (2) where the defendant moves that he be allowed to submit to an examination *431adminstered by an expert chosen by the Commonwealth; (3) where the defendant moves to be allowed to submit to an examination conducted by a jointly selected examiner, or by examiners designated by .the defendant and by the Commonwealth; or (4) where the defendant moves that the court appoint an examiner. In all four instances, the defendant would agree in advance that the results would-be admissible irrespective of the outcome of the tests.8 Once an acceptable motion has been made and is allowed by the court, after written findings as to the voluntariness and understanding by the defendant, the test can be administered. Before admitting the results, the judge should engage in the type of voir dir.e inquiry we have referred to above. After making appropriate findings, he may then, in his discretion, admit the examiner’s testimony concerning the test results as evidence to be considered with all other evidence. The Commonwealth would, of course, be entitled to a copy of the polygraph test results.
Here it is important to emphasize the relationship between our holding and the defendant’s Fifth Amendment to the United States Constitution right against self-incrimination, and its waiver. The polygraph results are essentially testimonial in nature and therefore a defendant could not be compelled initially to take such an examination on the Commonwealth’s motion.9 Thus, if the defendant on his own initiative requests an examination *432and agrees (knowingly and with understanding) to the admission of the results regardless of outcome, he has to that extent waived his Fifth Amendment rights. Therefore, as we have previously indicated, before granting a defendant’s motion that he be allowed to submit to a polygraph examination, the court must inform him of his constitutional rights. Next, if the defendant wishes to waive that right, the court must assure (with appropriate findings) that the waiver is made “voluntarily, knowingly and intelligently.”10
Another important question concerns the right of cross-examination. We wish to make it clear that by selecting or agreeing to an expert to administer a polygraph examination, a defendant does not in any way preclude himself from cross-examining that expert if his testimony turns out to be unfavorable to the defendant’s position when the expert’s testimony is offered by the Commonwealth. Moreover, the possibility of vigorous cross-examination by a defendant in this context, in addition to protecting a defendant’s basic right to confront witnesses against him, may serve as an incentive for an examiner to make every effort to assure that his examination is properly and thoroughly conducted. In this regard we think it important that both parties, depending on the outcome of the polygraph results and by whom the expert is called as a witness, have an equally broad scope of cross-examination available to them at trial regardless of who originally selected the expert.
Professor Wigmore has stated that “[i]f there is ever devised a psychological test for the valuation of witnesses, the law will run to meet it.” Wigmore, Evidence (2d ed.) § 875 (1923). Admittedly, our holding today (rather than “running to meet it”) is but a cautious first step toward the acceptance of polygraph testing. The guidelines we have laid down are not intended to be all inclusive. The benefit of time and the experience gained under the new practice we *433have established may, in the future, indicate the desirability of a more detailed and comprehensive set of court rules in the area of polygraphy testing and the admissibility of its results in evidence. In view of the extensive debate and controversy which still exist as to the use of polygraphy as an aid to the truth-finding function of the courts, we believe that further learning, experimentation and experience are necessary before more comprehensive and all encompassing rules are considered for adoption.
On the record before us it is clear that the defendant’s motions concerning polygraph tests were not denied by the trial judge as a matter of discretion but rather as a ruling of law.11 In any event, the defendant is entitled to the benefit of the doubt on this score, especially when it is remembered, as we noted in the first appeal, supra, that the case against him is “very largely circumstantial.” The defendant may file within thirty days a motion for a new trial in the Superior Court. The motion for a new trial will be limited to and dependent on the single issue of whether the judge will allow, as a matter of discretion, consistent with our holdings, the defendant’s motion for a polygraph test. See Earl v. Commonwealth, 356 Mass. 181 (1969).
II.
In the circumstances, following established precedent in the United States Supreme Court, and in this connection speaking for myself and not necessarily for the concurring Justices, I believe it is appropriate to make brief comment on the dissenting opinions. They show unusual and pre*434mature concern about alleged problems which time may resolve. From Justice Quirico’s dissent one might conclude that the trial courts will immediately be overwhelmed with polygraph testimony. I do not believe this will happen. Only under shárply defined and limited circumstances and conditions may the trial judge, in his discretion, permit such evidence to-be admitted. It is reasonable to suppose that a careful and experienced judge will consider the admission of the evidence, in a very close case,12 when unusual facts and circumstances warrant such a procedure, and in the interests of justice. It is also reasonable to conclude that such circumstances will not arise with great frequency.
Both Justices Quirico and Kaplan urge that the entire matter be sent to a commission for study. The analogy made to the recent study of ci /il rules of procedure is, indeed, mixing apples with oranges. The civil procedure study dealt with matters wholly within the expertise of trained lawyers and judges. Polygraphy simply does not fit into this category. Moreover, polygraphy has, for decades, been the subject of study, debate and controversy. It is too late in the day for just another study. Rather, the time is ripe for cautious judicial examination and evaluation. The experience gained may well lead to a total rejection of the concept. On the other hand, it could develop into a very *435useful tool in the administration of criminal justice. Actual testing in the courts is necessary before this determination can be made.13
The argument is made that only a few jurisdictions have seen fit to admit polygraphic evidence. I agree that it is much easier to wait until the majority of the States have done the arduous spadework in resolving novel, difficult, and complex questions of law, and then fall in line. However, our preference should be to work out our own destiny.
The dissenters urge that more detailed guidelines for the benefit of trial judges are needed. Here, we should not underestimate the resourcefulness and the ingenuity of experienced trial judges in dealing with novel situations where exact blueprints have not been provided. Nor should trial judges be unduly shackled in the exercise of their judgment. It is not the legitimate function of the courts of last resort to provide complete and detailed plans and specifications in anticipation of all possible problems and situations. The experienced trial judge can usually cope with them as they arise. Moreover, I do not believe that appellate judges are necessarily better informed or equipped to formulate in advance all inclusive guidelines for the trial judges. We have had ample experience on this score in recent years with the Supreme Court’s efforts in dealing (or rather attempting to deal) with pornography, arrest, and search and seizure. In many instances, the guidelines have created more problems than were resolved. Our primary job is to decide whether the trial judge is right or wrong and then state sound reasons (hopefully) for our decisions. For many generations the trial judges have *436provided the cutting edge for much of the law’s progression. From their decisions, together with the overview of the appellate courts and the process of trial and error, the common law has evolved and progressed. In the main, this practice should be followed.
In the instant case, it is not necessary or wise to try to anticipate all procedural problems which may eventuate. Here' a limited and cautious step is being taken, permissible only on motion of the defendant and subject to the exercise of the judge’s discretion. Apart from the general guidelines provided in the opinion, it is wiser to let actual experience provide the learning for possible future guidelines.
Thus, if in the first instance, an experienced and courageous trial judge makes the decision to admit polygraph evidence, it would be best to let him exercise his judgment, subject to our review for possible error. Most trial judges are fully capable of meeting with and resolving the hypothetical problems raised in the dissenting opinions.
In any event, the last thing that should be considered is the formation of still another commission to undertake still another study to gather still more dust. Rather than take this dubious road, it would be far better to do nothing and wait for the courts in other jurisdictions to establish the merits and demerits of polygraphy through the time-tested adversary process.
HI.
In light of this disposition of the polygraph issue, which creates the possibility that the juvenile’s motion may again be denied, it is necessary for us to deal with other grounds for reversal argued by the juvenile. The first concerns testimony by a Dr. Osgood, the medical examiner who performed the autopsy on the body of the victim. The juvenile contends that the trial court erred in allowing Dr. Osgood to state that in his opinion the blade of a knife, introduced in evidence as the alleged instrumentality of the *437crime, could have inflicted the fatal wound. The blade was approximately three and one-half inches long; the handle was missing. The depth of the knife wound causing the victim’s death was (a) between three to five centimeters from the outer skin to the heart, plus (b) approximately seven centimeters into the heart itself, or a total of between approximately four and five inches. From these facts, and from his observations that the victim had a “penetrating wound through his skin, chest wall, into his heart,” Dr. Osgood concluded that the blade could have caused the fatal wound, and that the reason for the wound’s depth was that the victim was probably “folded over” at the time the blade was inserted, causing the knife to penetrate more deeply. The juvenile objects to the characterization of the victim’s possible position when the knife was allegedly inserted, contending that it is pure conjecture and is an unjustified assumption used to buttress the doctor’s conclusion that the blade in question caused the victim’s death. We disagree. A physician who has performed an autopsy may testify that the injuries which he observed could have been caused in a particular way or by a specified instrumentality. Commonwealth v. Belenski, 276 Mass. 35, 44 (1931). Commonwealth v. LePage, 352 Mass. 403, 418 (1967). Commonwealth v. Boudreau, 362 Mass. 378, 381 (1972). He is qualified to give such testimony because he is experienced in anatomy and in the study of the effects of blows and wounds inflicted on a body. Therefore, his opinion on a matter such as the position of a body during or after a knife stab, based on his medical knowledge and observations, is not a mere speculative assumption and was properly admitted.
The juvenile’s next argument relates to testimony of another medical expert, Dr. Luongo. He was asked by the Commonwealth, “[P] resuming,... that if the jury finds as a fact that when this wound was inflicted, it had attached to it a handle similar in size and shape to the handle which is affixed to Commonwealth’s Exhibit No. 11 — Doctor, would you now have an opinion as to — with that handle attached, could that blade, which is Commonwealth’s *438Exhibit No. 8, cause the injury which you and Dr. Osgood observed in the upper left chest of . . . [the victim]?” The juvenile contends that this was an improper hypothetical question in that there was no independent evidence which supported the assumption that the blade was ever in fact attached to a handle like that attached to the blade introduced as exhibit 11. No handle was ever found. The alleged murder weapon, the juvenile argues, may never have been attached to a handle, or may have been attached to a different handle, or may have become separated from its handle before the time the stabbing allegedly took place. We believe that the existence of these possibilities did not make the hypothetical question improper. A medical expert may testify, in response to a hypothetical question, that the type of injuiy he has observed is consistent with the Commonwealth’s theory of how the wound was inflicted, so long as that theory is based on other evidence already introduced. Commonwealth v. Burke, 339 Mass. 521, 530 (1959). The knife introduced as exhibit 11, complete with handle, and with a blade similar in size and description to the blade which the Commonwealth maintained was the instrumentality of death, was admitted without objection and was clearly intended to raise the inference that the alleged murder weapon at one time was attached to a handle. It is a matter of common knowledge that knives have handles. Counsel for the juvenile asked Dr. Luongo, “You know knives generally have handles; do they not?” Of course the juiy could ultimately reject the inference that the blade had a handle at the time of the crime, and along with it Dr. Luongo’s response to the hypothetical question, but we perceive no reason why the Commonwealth should have been prevented from pursuing its basic theory as to how the crime was committed. See Commonwealth v. Moore, 323 Mass. 70, 74-75 (1948).
On other grounds, the juvenile contends that he was entitled to a mistrial. The victim’s father, in a nonrespon-sive answer, remarked on the witness stand that “I saw him [the juvenile] abusing Jimmy [the victim]” on an occasion before the murder took place. There can be no question that *439the remark was improper. The trial judge properly struck that comment, and with clear and forceful language instructed the jury not to consider it.14 The juvenile contends that a mistrial should have been declared. This is a matter for the judge’s discretion, and in light of the fact that the judge took other appropriate measures to negate the possible prejudice stemming from the witness’s remark, we cannot say that his decision not to grant a mistrial was reversible error.
The juvenile also contends that the judge erred in allowing a young friend of the juvenile to testify that the juvenile appeared “scared” on the evening when the victim was allegedly murdered. The juvenile contends that this answer was not admissible because the Commonwealth had not previously established that the witness was familiar with the juvenile’s normal behavior. We disagree. Familiarity with a defendant, although it may go to the weight of the evidence, is not a prerequisite to admission of a witness’s conclusory description based on observation of a defendant’s “condition of mind” on a particular occasion. Commonwealth v. Bonomi, 335 Mass. 327, 339 (1957). Even if it were, such familiarity was circumstantially demonstrated by the witness’s additional testimony that he knew the juvenile for a period of years and saw him on a weekly basis.
The juvenile’s final argument concerns the judge’s refusal to charge the jury in accordance with requested instructions. Some background information is necessary to an understanding of the basic issue. The complaint against the juvenile specified that he committed homicide “with a Grant Maid Stainless U. S. A. table knife.” At trial, the Commonwealth introduced the blade of such a knife. Before the judge charged the jury, the juvenile requested a specific instruction that the jury must find, beyond a reasonable doubt, that this particular blade had actually *440caused the victim’s death. The judge denied that request and the juvenile claims that the ruling was erroneous and prejudicial. The thrust of the argument is that in response to the language of the complaint the juvenile directed his defence to disproving that the particular knife was used, and that therefore it would be unfair to allow the jury to consider any other possible instrumentalities of death. Such an argument has been raised, and rejected, before. See Commonwealth v. Jordan, 207 Mass. 259, 267 (1911). The judge was correct in denying the juvenile’s request. The means by which a murder is committed do not constitute an essential element of the crime of murder under G. L. c. 265, § 1. Language in an indictment or complaint specifying the means of death is therefore superfluous. A defendant is not entitled to an acquittal by reason of the Commonwealth’s failure to prove unnecessary allegations in the description of a crime. G. L. c. 277, § 35. In any event, we find no prejudice. The complaint in this case clearly informed the juvenile that he was being charged with murder under c'. 265, § 1. As such, he was on notice that if the Commonwealth were to prove all the essential elements of that crime, he would be convicted. Therefore, it cannot be said that as a result of the superfluous language of the complaint the defendant did not understand the crime charged, or was unable to prepare a proper defence. While as a matter of strategy the juvenile might have felt it best to focus his efforts on the question whether the particular knife was used, he was not forced or misled by the Commonwealth to take that approach.
Having considered and disposed of the juvenile’s (non-polygraph) arguments we hold as follows: If the juvenile fails to file a motion for a new trial within thirty days or if the motion is filed and after a hearing thereon it is denied as a matter of discretion, the judgment shall be affirmed. In the alternative, if the defendant’s motion for a new trial is allowed, the judgment shall be reversed, the verdict shall be set aside, and the case shall be remanded for a new trial.
So ordered.
At the previous trial there was a jury verdict of delinquency by reason of murder in the second degree which was vacated by us in Commonwealth v. A Juvenile, 361 Mass. 214 (1972).
See, e.g., United States v. DeBetham, 348 F. Supp. 1377 (S. D. Cal. 1972), affd. 470 F. 2d 1367 (9th Cir. 1972), cert. den. 412 U. S. 907 (1973); United States v. Ridling, 350 F. Supp. 90 (E. D. Mich. 1972); United States v. Zeiger, 350 F. Supp. 685 (D. D. C. 1972), revd. 475 F. 2d 1280 (D. C. Cir. 1972); States. Valdez, 91 Ariz. 274 (1962). Helpful commentaries include Reid and Inbau, Truth and Deception (1966); Kaplan, The Lie Detector: An Analysis of its Place in the Law of Evidence, 10 Wayne L. Rev. 381 (1964); Skolnick, Scientific Theory and Scientific Evidence: An Analysis of Lie-Detection, 70 Yale L. J. 694 (1961); note, 20 Drake L. Rev. 330 (1971); note, 53 B. U. L. Rev. 375 (1973).
See also Reid and Inbau, at 4 (fn. 2, supra), who consider “the ability, experience, education, and integrity of the examiner” to be “the most important factor” involved in the use of any polygraph.
See Reid and Inbau, at 226-232 (fn. 2, supra).
Horvath and Reid, the Reliability of Polygraph Examiner Diagnosis of Truth and Deception, 62 J. of Crim. L., Criminology and Police Science, 276 (1971). Raskin, An Experimental Study of Field Techniques in “Lie Detection,” in Zimmerman, The Polygraph in Court, at 94 (1972).
Reid and Inbau, for example, suggest that a polygraph expert should have the following credentials before being permitted to testify: (1) a college degree; (2) at least six months of internship training under an experienced, competent examiner or examiners with a sufficient volume of case work to afford frequent supervised testing in actual case situations; (3) five years’ practical experience. Truth and Deception, supra, at 257 (1966).
Charles Zimmerman was trained in polygraph techniques while serving in the United States Army under a Department of Defense Program. Subsequently , he served for five years as a polygraph examiner at the Military Police Crime Laboratory. Thereafter he was an adviser for lie detection to the Headquarters, European Command for the United States Army. While in this capacity, he conducted polygraph tests for the CIA, CIC, CID and Interpol. He has lectured at various universities on the polygraph, and participates regularly in various seminars and refresher courses. He is the author of four works on the polygraph. Throughout his career, he has performed between 22,000 and 30,000 polygraph examinations.
In the instant case, the juvenile was aware of the favorable polygraph results before making his motion. He would therefore be restrictedto options (2), (3), and (4) unless he makes a new selection of another expert and agrees in advance to the admissibility of the test results.
See Schmerber v. California, 384 U. S. 757, 764 (1966), where the court, in dicta, offered these very pertinent remarks: “There will be many cases in which ... [the distinction between testimonial evidence and real or physical evidence] is not readily drawn. Some tests seemingly directed to obtain ‘physical evidence,’ for example, lie detector tests measuring changes in body function during interrogation, may actually be directed to eliciting responses which are essentially testimonial. To compel a person to submit to testing in which an effort will be made to determine his guilt or innocence on the basis of physiological responses, whether willed or not, is to evoke the spirit and history of the Fifth Amendment. Such situations call to mind the principle that the protection of the privilege ‘is as broad as the mischief against which it seeks to guard,’ Counselman v. Hitchcock, 142 U. S. 547, 552.” See also Bowen v. Eyman, 324 F. Supp. 339 (D. Ariz. 1970); note, 53 B. U. L. Rev., supra, at 392-396 (1973).
Miranda v. Arizona, 384 U. S. 436, 444 (1966).
Justice Quirico’s dissent argues the contrary on the basis of a truncated version of the trial judge’s ruling denying the juvenile’s motion. With all deference, that excerpt does not reveal the full character of the judge’s position. Other more pertinent remarks clearly indicate that the judge was personally convinced that the juvenile had established a very convincing case for the admission of polygraph results (“When conducted by competent polygraph examiners under proper examination conditions, polygraphic testing possesses a high degree of reliability and scientific acceptability. [The p]olygraphic test of the juvenile was conducted by a qualified and highly competent polygraph *434examiner.”) However, he felt that such a ruling “should [not] be made in the first instance by the trial judge.”
In any event, our holding today will not preclude the judge, if he so desires, from exercising his discretion on remand to deny the juvenile’s motion. Therefore, if that was his initial intention, under our opinion he may do so again. On the other hand, our decision today leaves it open in the future for other judges to allow such motions in cases wherein they deem it desirable and proper. Finally, the majority opinion makes its intention clear not to overrule Commonwealth v. Fatalo, supra, and not to make polygraphic evidence generally admissible.
Recently, a Superior Court judge with long prior experience (and an outstanding reputation) as a trial lawyer, at the conclusion of the evidence, offered the defendant the opportunity to take a polygraph test with the stipulation that the case would be dismissed if the defendant successfully passed the test. The test was taken with success and the case was dismissed to the complete satisfaction of all parties. This is cited not as an example to be followed routinely but only as an indication that, on occasion, wise and experienced judges welcome additional help in resolving very close factual issues.
We recently had occasion in Commonwealth v. McAlister, post, 454 (1974), to comment on the value of out-of-court studies as an aid to judicial decision making. Although the studies referred to in that case are dissimilar (they were directed to the question whether “death-qualified” jurors are conviction-prone), the analogy is not lost, and the point made in that case bears repeating here. “The most serious difficulty, of course, is that all of these studies were outside of actual trials. No such simulated cases can reproduce the great responsibility which exists when ‘in the solemnity of a court room a defendant is tried and his reputation and his liberty or his life are at stake.’ ” Id. at 461, quoting in part from Commonwealth v. Blackburn, 354 Mass. 200, 204 (1968).
From the record it is clear that the judge reduced the reference to “abusing” to a parent’s nervous account of a possible scuffle or pushing between the two boys. He thus attempted to remove from the case any suggestion of “extreme physical treatment” or “sexual misconduct.”