The individual defendant and the corporate defendant were found guilty in February, 1976, after a jury waived trial, on all counts of indictments charging them with having possession of obscene matter in June, 1975, with intent to disseminate it. While these appeals were progressing to this court,2 we decided three cases involving the obscenity statute which was enacted in June, 1974 (see St. 1974, c. 430), after this court’s holding in Commonwealth v. Horton, 365 Mass. 164 (1974), that our previous obscenity statute was unconstitutional. See Commonwealth v. 707 Main Corp., 371 Mass. 374 (1976); Commonwealth v. Thureson, 371 Mass. 387 (1976); District Attorney for the N. Dist. v. Three Way Theatres Corp., 371 Mass. 391 (1976). The appellants ask us to reconsider certain of our holdings in those cases, and they challenge the judge’s exclusion of a public opinion survey from evidence. We affirm the judgments.3
*7981. In Commonwealth v. 707 Main Corp., supra at 383-384, we held that G. L. c. 272, §§ 28C-31, were not unconstitutionally vague under either the Constitution of the United States or the Constitution of the Commonwealth. The appellants grant that the material which they possessed for sale portrayed sexual conduct as defined in G. L. c. 272, § 31, and concede that the definition of sexual conduct is not vague. They argue, however, that the statutory definition of obscene matter is unconstitutionally vague because of that language in G. L. c. 272, § 31, as appearing in St. 1974, c. 430, § 12, which requires that the matter, taken as a whole, must appeal “to prurient interest of the average person, applying the contemporary standards of the commonwealth” and must depict or describe “sexual conduct in a patently offensive way . . . .” In Commonwealth v. 707 Main Corp., supra at 384, we noted that the statutory definition met the requirements expressed by a majority of the Supreme Court of the United States in Miller v. California, 413 U.S. 15, 24-27 (1973). We concluded that, in the typical case, the trier of fact must use an average citizen of Massachusetts as the standard for determining whether particular matter appeals to the prurient interest of the average person and for determining whether the matter depicts or describes sexual conduct in a patently offensive way. 371 Mass, at 384.
The appellants argue that the statutory standard of a hypothetical average person is vague and difficult to apply. They contend, without any proof on the record, that there is no Statewide standard concerning obscenity and argue that, even if there were such a standard, a distributor of sexually oriented material must identify that standard at his peril. The Supreme Court of the United States has concluded that language substantially equivalent to our statutory definition of “obscene” is not unconstitutionally vague. See Ward v. Illinois, 431 U.S. 767, 771-773 (1977); Smith v. United States, 431 U.S. 291, 308-309 (1977), and cases cited. The only question before us is whether the Constitution of the Commonwealth should be construed to require *799greater specificity. We rejected any such claim in Commonwealth v. 707 Main Corp., supra, and see no reason to change that conclusion at this time. If material displays “sexual conduct” as precisely defined by § 31, the person is adequately warned that the material may also fall within the other statutory elements of obscenity. There are numerous situations in the criminal law where conduct which fails to meet the standard of reasonableness is criminal. The trier of fact in such an instance must assess the defendant’s conduct in terms of the way in which a reasonable person should have acted. The use of a standard of reasonableness has never been held unconstitutionally vague under our Constitution, and the statutory standard in this case has not been shown to be significantly different in its concept from a measure of reasonableness. See Smith v. United States, supra at 308; Hamling v. United States, 418 U.S. 87, 104-105 (1974). Granting that the standard is incapable of precise articulation, we do not consider the definition of “obscene” unconstitutionally vague as applied to the appellants.
2. The appellants next urge us to reconsider our holdings that, without the introduction of expert evidence on Commonwealth norms, the material itself may be sufficient evidence for the trier of fact to find obscenity. District Attorney for the N. Dist. v. Three Way Theatres Corp., 371 Mass. 391, 393-394 (1976). Commonwealth v. Thureson, 371 Mass. 387, 389 (1976). Commonwealth v. 707 Main Corp., 371 Mass. 374, 384-385 (1976). See Jenkins v. Georgia, 418 U.S. 153, 159-160 (1974); Hamling v. United States, 418 U.S. 87, 104 (1974); Kaplan v. California, 413 U.S. 115, 121 (1973); Paris Adult Theatre I v. Slaton, 413 U.S. 49, 56 (1973). We see no reason to change our view on the subject.
The appellants concede that the weight of authority supports the conclusion that expert testimony is not required as part of the prosecution’s proof in the typical obscenity case.4 *800Of course, absent favorable expert testimony, the Commonwealth risks that the trier of fact will be unable to arrive at a conclusion concerning Statewide standards. A defendant is entitled to rulings or instructions that, if the trier of fact cannot determine Commonwealth norms, the defendant is entitled to a finding in his favor, and that the trier of fact must apply, not personal views, but the views of an average person in the Commonwealth as a whole. Although the defendant may offer his own evidence concerning Statewide standards (Commonwealth v. 707 Main Corp., supra at 384), the burden of proving a violation of those standards beyond a reasonable doubt remains on the Commonwealth.
We leave to another occasion, if it should ever arise, resolution of any challenge to the statute by proof that there is no such thing as (1) a “prurient interest of the average person,” (2) sexual conduct which is patently offensive with reference to contemporary Commonwealth norms, or (3) “contemporary standards of the commonwealth.” The appellants have not met their heavy burden of demonstrating the unconstitutionality of the Commonwealth’s obscenity statutes. We are not persuaded that there is no rational basis for the Legislature to conclude that there are ascertainable Statewide standards, even though the citizens of the Commonwealth differ from each other in numerous ways, including upbringing, place of residence, age, education, religion, and sex. The existence of Statewide standards lies at the heart of the Commonwealth’s obscenity statute because such universal standards must exist if a jury selected from only one county is to apply them. Of course, if such standards do not exist, the statute must fail for unconstitutional vagueness.
3. We see no occasion to change our views, expressed in Commonwealth v. 707 Main Corp., supra at 382, concerning the nature of the proof of a defendant’s knowledge necessary for a conviction under G. L. c. 272, § 29. Section 29 requires proof that the defendant possessed matter which was obscene, “knowing it to be obscene.” Section 31 of *801G. L. c. 272, as appearing in St. 1974, c. 430, § 12, defines “knowing” as “a general awareness of the character of the matter.” In our opinion in Commonwealth v. 707 Main Corp., supra at 383, we said that “knowledge of legal obscenity is not required,” and noted that the statute comported with “the constitutional requirement that a defendant have knowledge of the matter’s contents and general character before a criminal conviction . . . may be obtained.” Id., citing Hamling v. United States, 418 U.S. 87, 123 (1974). Commonwealth v. Thureson, 371 Mass. 387, 389-390 (1976). In adhering to this position, we discern no violation of a defendant’s right to due process under the Declaration of Rights.
4. We come finally to an issue with which this court has not dealt previously. The appellants argue that the judge improperly excluded a public opinion survey from evidence. Although, as will be seen, public opinion surveys are admissible in certain circumstances, we agree with the judge’s decision to exclude the appellants’ public opinion survey.
A properly conducted public opinion survey, offered through an expert in conducting such surveys, is admissible in an obscenity case if it tends to show relevant standards in the Commonwealth. We see no meaningful distinction between a properly conducted piiblic opinion survey offered to show community norms and the testimony of an expert who states his views on the opinion of the public concerning the portrayal of certain allegedly obscene conduct. We have already recognized the admissibility of expert testimony of the latter type. We have said, citing Paris Adult Theatre I v. Slaton, 413 U.S. 49, 56 (1973), that triers of fact “may consider expert testimony on the subject of Statewide standards, if any is offered in evidence, but also may disregard such evidence because the matter at issue may be per se sufficient evidence for a finding of prurience in most cases.” Commonwealth v. 707 Main Corp., 371 Mass. 374, 384-385 (1976). Although expert testimony may be excluded, in the judge’s discretion, if a subject is within the common knowledge of the average juror, the line between matters of com*802mon knowledge and matters beyond common knowledge often is not precise. If such expert testimony may give the jury appreciable assistance in resolving a fact question, it is admissible in the judge’s discretion. Commonwealth v. Fournier, 372 Mass. 346, 350 (1977). Commonwealth v. Boyd, 367 Mass. 169, 182 (1975). Where the question is whether portrayals of sexual conduct are “obscene” under the statutory definition, it would be a rare case in which testimony from a qualified expert should be excluded on the ground that it would not be helpful to the trier of fact. Similarly, a properly conducted public opinion survey should be admitted. The question then is what is a properly conducted public opinion survey.
If the universe surveyed is relevant, if the sample questioned is representative of the relevant universe, if the questions are in a form appropriate to obtain unbiased answers within a reasonable margin of error, and if the pollster is qualified, the weight of authority supports the admission of a public opinion survey tending to prove a fact relevant to a material issue. See the leading, oft-cited case, Zippo Mfg. Co. v. Rogers Imports, Inc., 216 F. Supp. 670, 682 et seq. (S.D.N.Y. 1963). See also Randy’s Studebaker Sales, Inc. v. Nissan Motor Corp. in U.S.A., 533 F.2d 510, 520 (10th Cir. 1976); Grotrian, Helfferich, Schulz, Th. SteinwegNachf. v. Steinway & Sons, 523 F.2d 1331, 1341 (2d Cir. 1975); President of Colby College v. Colby College-N.H., 508 F.2d 804, 809 (1st Cir. 1975); Holiday Inns, Inc. v. Holiday Out in America, 481 F.2d 445, 447 (5th Cir. 1973); Sample, Inc. v. Porrath, 41 App. Div. 2d 118, 123 (1973), aff’d on this opinion, 33 N.Y.2d 961 (1974); 6 J. Wigmore, Evidence § 1704 n.l (Chadbourn rev. 1976); 2 S. Card, Jones on Evidence, Civil and Criminal § 10:8, at 278-279 (6th ed. 1972); Annot., 76 A.L.R.2d 619 (1961); Manual for Complex Litigation, 104-106 (West Pub. Co. 1977), discussing the admissibility of the results of polls; Zeisel, The Uniqueness of Survey Evidence, 45 Cornell L.Q. 322 (1960); Sorensen and Sorensen, The Admissibility and Use of Opinion Research Evidence, 28 N.Y.U.L. Rev. 1213 (1953). However, where *803the methodology of the survey is deficient, the trial judge should exclude it. See, e.g., Bank of Utah v. Commercial Security Bank, 369 F.2d 19, 27 (10th Cir. 1966), cert, denied, 386 U.S. 1018 (1967) (unrepresentative sample used); People v. Thomas, 37 Ill. App. 3d 320, 325-326 (1976) (inadequate foundation for survey in obscenity case); Regina v. Times Square Cinema Ltd., 4 C.C.C.2d 229 (Ont. Ct. of App. 1971) (improper universe).
We are not inclined to pause long to resolve whether a survey of people’s opinions is hearsay and, if it is, whether it is admissible under the state of mind exception to the hearsay rule. Numerous authorities have admitted particular surveys under that hearsay exception. See Zippo Mfg. Co. v. Rogers Imports, Inc., supra at 683; Holiday Inns, Inc. v. Holiday Out in America, supra at 447; Morelli v. Board of Educ., Pekin Community High School Dist. No. 303, 42 Ill. App. 3d 722, 730-731 (1976); 2 S. Card, Jones on Evidence, Civil and Criminal supra, § 10:8 at 278-279; Regina v. Prairie Schooner News Ltd., 1 C.C.C.2d 251, 266 (Man. Ct. of App. 1970).5 The focus should be on the techniques employed rather than on whether hearsay is involved. See Fed. R. Evid. 703 and Note of the Advisory Committee, 56 F.R.D. 183, 283 (1972). A properly conducted public opinion survey itself adequately ensures a good measure of trustworthiness, and its admission may be necessary in the sense that no other evidence would be as good as the survey evidence or perhaps even obtainable as a practical matter. See Zippo Mfg. Co. v. Rogers Imports, Inc., supra at 683-684; American Luggage Works, Inc. v. United States Trunk Co., 158 F. Supp. 50, 53 (D. Mass. 1957). Of course, the judge will have to determine in his discretion whether *804the methodology of the survey was adequate to justify its admission.6 In certain instances, any weaknesses in the manner in which a poll was conducted might affect only the weight to be accorded the survey results rather than the admissibility of the survey in evidence.
In light of these principles, we consider the public opinion survey prepared for the defendants in this case. The defendants made an offer of proof of the testimony and exhibits relating to their survey. Two hundred adults, all residents of Boston, divided evenly by sex, were obtained from all sections of Boston by telephone solicitations conducted evenings, and each was interviewed. Each was offered $10 to come to an office in downtown Boston for an interview on an undisclosed subject relating to a pending court case. Trained personnel conducted the interviews shortly before trial. The defendants intended to introduce the results of the survey through an expert experienced in conducting public opinion surveys, who would have testified that the margin of error in the survey ranged from 6 % to 10%.
The questions largely sought the personal views of each person interviewed: whether, in particular circumstances, he or she would be willing to have motion picture films shown or magazines sold depicting human sexual conduct. One question asked, for example, whether the individual would “personally be willing to have motion picture films or magazines showing human sexual intercourse between members of the opposite sex (sic) shown or sold” in (a) residential neighborhoods of Boston, (b) general commercial or business areas in Boston, (c) Boston adult entertainment districts, (d) under conditions where minors were excluded, or (e) in places clearly marked so that anyone not wanting to see them could avoid them. The interviewer sug*805gested three answers: would be willing, would not be willing, or “ [djon’t care one way or the other.” If other answers, such as no opinion or a qualified approval, were given, those answers also were tabulated. Similar questions were asked concerning each subject’s willingness to allow the sale or showing of films or magazines depicting human masturbation, oral sex, or homosexual acts. Two other questions inquired into each subject’s willingness to allow the sale of particular magazines which were shown to him or her. One of those magazines was the subject of one count in an indictment in this case.
As would be expected, the willingness of the subjects interviewed to have such films shown, or magazines sold, increased as the suggested place of the showing or sale moved from residential to adult entertainment areas, when minors were excluded from involvement, and when the nature of the material to be shown or sold was plainly indicated. In general, males were more willing to allow the showing or sale of such materials than females.
It is important to note certain facts not set forth in the offer of proof. There was no indication that the method of selection of the subjects to be interviewed assured a representative sample of the citizens of Boston. One might suspect that certain persons would decline to participate because of the method by which they were approached or because of their unwillingness or inability to take the time to participate in such interviews. The selection process was not shown to be free from producing a bias in the survey results.
The interrogation of residents of only Boston raises the question whether the survey results are competent to prove the standards of the Commonwealth as a whole. However, because the obscenity statute assumes the existence of a uniform, Statewide standard, we should not reject a representative and otherwise valid survey limited to a population as large as that of Boston.
Finally, and most significantly, we note the absence of any indication that the willingness, the lack of willingness, or the indifference of a group to the sale of sexually explicit *806magazines or the showing of sexually explicit films has any relevance to any issue material to this case. The survey results apparently were offered as bearing on the question whether the films and magazines involved in this case displayed sexual conduct in a patently offensive way. The offer of proof made no attempt to connect an acceptance of, or an indifference to, the showing or sale of that material with whether the particular sexual conduct involved in this case was depicted or described in a patently offensive way. Perhaps many people would not object to others’ seeing such material, although they themselves regard that material as patently offensive. The offer of proof did not explain the relationship of the offered evidence to this fundamental factual question of patent offensiveness.
Because the offer of proof failed to demonstrate the representativeness of the persons interviewed and failed to show that the survey results were relevant to any material issue in the case, the judge was warranted in excluding the survey and expert testimony concerning it.
Judgments affirmed.
We granted the defendants’ application for direct appellate review.
The appellants do not argue here, and explicitly waived at trial, any claim that these criminal proceedings must be dismissed because in rem proceedings were not commenced first under G. L. c. 272, §§ 28C, 28D, 28E, 28G, 28H. On the defendants’ insistence, such proceedings could have been required as to the publications involved here if they were “books.” The statute does not apply by its terms to films. Although the contrary has been suggested (see Liacos, J., concurring in Commonwealth v. Zone Book, Inc., 372 Mass. 366, 378 [1977]), the absence of a showing of the commencement of a previous civil proceeding is not a jurisdictional defect. It is a matter which may be raised by the defendant, but need not be considered otherwise. Commonwealth v. Ferro, 372 Mass. 379, 384-386 (1977).
We recognize that expert testimony may be necessary where the appeal is to a deviant group. See Paris Adult Theatre I v. Slaton, 413 U.S. 49, 56 n.6 (1973).
In Canada, where the definition of obscenity is founded on “the undue exploitation of sex,” the courts have considered the admissibility of survey evidence. Lamont, Public Opinion Polls and Survey Evidence In Obscenity Cases, 15 Crim. L.Q. 135 (1972). The author of this article notes that “community standards” are considered in such cases and that “[cjriminal obscenity is an area of the law which is peculiarly suited to the use of survey evidence because of its very definition.” Id. at 136.
In Commonwealth v. Beneficial Fin. Co., 360 Mass. 188, 215 (1971), cert, denied sub nom. Farrell v. Massachusetts, 407 U.S. 910, and sub nom. Beneficial Fin. Co. v. Massachusetts, 407 U.S. 914 (1972), we held that the judge did not abuse his discretion in excluding tables based on interviews with persons not before the court.