GREANEY, J.

The defendant was charged, in a four-count indictment, with giving perjured testimony before a grand jury. G.L.c. 268, § 1. He waived trial by jury and, after a bench trial in the Superior Court, was found guilty on all counts. On each count, he was sentenced to a one-year term in a house of correction, the terms to run concurrently and with the sentences suspended and probation imposed for one year.

On appeal, the defendant argues four claims of error, only one of which has substantial merit. That argument presents the question whether the defendant has been subjected to multiple punishment in violation of the double jeopardy clause. Specifically, the defendant argues that the four statements charged as separate perjuries so overlapped in content as to bar conviction on all four counts.

The facts are not in dispute. In November, 1978, a special grand jury was convened to investigate allegations of fraud by parties providing services to the Medicaid program of the Department of Public Welfare (Department). One provider under investigation was Bay State Management Company, Inc. (Bay State), which owned and operated eight long term care facilities in Massachusetts, including the Quincy Nursing Home (Quincy). Since at least 1969, Quincy had paid wages to one Emma Boynton as a kitchen employee. The grand jury had information, however, that Boynton did not actually work at Quincy for a number of years when she was on its payroll. Rather, it was alleged that she worked during those years at the personal residence of one Michael Minkin, a director of Bay State.

The vice of this arrangement arises from the fact that Quincy was being reimbursed by the Department for wages paid to its employees. Under regulations of the Rate Setting Commission (Commission), a nursing home providing services for Medicaid is required to file an annual financial report on a form denominated RSC-1. 114.2 Code Mass. Regs. § 2.03 (1978). The Commission uses these reports to determine the rate at which the nursing home will be reimbursed by the Department. See generally Commonwealth v. Cerveny, 373 Mass. 345, 348-349 (1977). Although several factors enter into the calculation, that rate is largely determined by the operating expenses, including wages, reported by the nursing home each year. 114.2 Code Mass. Regs. § 2.06(1) (1978). These expenses are apparently reimbursed on a dollar for dollar basis in most instances.

Commission regulations, however, forbid reimbursement of any "[e]xpenses which are not directly related to the provision of patient care." 114.2 Code Mass. Regs. § 2.06(5)(f) (1978). Thus, if Emma Boynton did not actually work at Quincy for a number of years when she was paid as an employee, the expenses reported by Quincy, and consequently the payments made by the Department, would have been improperly inflated for those years. If established, these facts would have been grounds for initiating prosecutions under G.L.c. 266, § 30(1) (larceny by false pretense), G.L.c. 268, § 1A (perjury by written instrument), and G.L.c. 6A, § 35 (falsifying information required to be filed with the Commission). See Commonwealth v. Cerveny, supra at 346-347 nn. 2-4.

On April 10, 1979, the defendant, accompanied by counsel, appeared before the grand jury. He first testified that he had worked at Quincy since May, 1971, that he was head chef and kitchen supervisor, and that he scheduled the hours which Emma Boynton worked. The assistant attorney general (prosecutor) then asked the defendant a series of questions directed at various periods of Boynton's employment. In substance, the defendant was asked whether Boynton worked at Quincy:

(1) from January 1 through December 31, 1972;

(2) from January 1 through December 31, 1973;

(3) from January 1, 1972, through December 31, 1975;

(4) from May, 1971, through the present (i.e., April 10, 1979). The defendant answered each question in the affirmative. Each numbered response formed the basis for the perjury charged in the count similarly numbered in the indictment.

At trial, the defendant stipulated that the prosecutor's questions were material to the grand jury's investigation. See, e.g., Commonwealth v. Borans, 379 Mass. 117, 135-137 (1979). The defendant also stipulated that the preliminary elements required to prove perjury were present. See Commonwealth v. Geromini, 357 Mass. 61, 63-64 (1970). The case was tried on the issues whether the four statements were false, and whether any falsity was wilful and intentional. The defendant does not question the sufficiency of the Commonwealth's proof on those elements.

1. The defendant's principal argument is that the convictions on all four counts are flawed on the ground of multiplicity. This argument proceeds on the view that the substance of the perjuries charged in counts 1 and 2 are included within count 3, and the substance of counts 1, 2 and 3 are included within count 4. Because of this, the defendant urges that the convictions on three of the counts should be vacated, leaving one conviction on either count 3 or count 4.

We have found no Massachusetts case which addresses the problem of multiple punishments in the context of perjury. There is considerable case law elsewhere, both Federal and State. Proper analysis of the case calls for a review of those decisions first, followed by discussion of the parties' contentions seeking (improperly in our opinion) to apply jeopardy principles involving lesser included offenses under the "same evidence" test. We then look to the statute itself to determine whether it was the Legislature's intent to allow separate convictions for the perjuries here (concluding that it was and that the prosecutor's choice of questions did not result in improper fragmentation of the offenses). We conclude that, since each count involves a lie about a period of time which is separate and distinct, the four perjuries are not substantially identical and the convictions can stand.

A. Cases on Multiplicity of Perjury Convictions.

The defendant relies on the leading case of Gebhard v. United States, 422 F.2d 281 (9th Cir. 1970), which states the prevailing view as follows: "If [the defendant] in fact told separate lies, each of which could have hindered the grand jury in its investigation, then he could properly be separately charged for each lie. On the other hand, we do not think it proper that the government bludgeon a witness who is lying by repeating and rephrasing the same question, thus creating more possible perjury counts. . . . [By so doing,] a prosecutor could run up a possible perjury sentence indefinitely merely by repeating the same question. Single punishment for a single lie should suffice." Id. at 289-290.

The Commonwealth concedes that "[t]he offense of perjury may not be compounded by the repetitious asking of the same question." Masinia v. United States, 296 F.2d 871, 880 (8th Cir. 1961). See also Brown v. Ohio, 432 U.S. 161, 169 (1977); Commonwealth v. Winter, 9 Mass. App. Ct. 512, 526 (1980). It maintains, however, that the four convictions are not based on the same perjury, as the defendant's answer to each successive question involved a new lie about a different period of Boynton's employment. In this view, the defendant told four "separate and distinct lies," and "the proof of each falsehood required the establishment of different facts." United States v. Nixon, 634 F.2d 306, 313 (5th Cir. 1981). For that reason, it is argued, "each answer constituted a separate incident of perjury." United States v. Masters, 484 F.2d 1251, 1253 (10th Cir. 1973).

As to the overlapping portions of the periods charged, the Commonwealth relies on United States v. Doulin, 538 F.2d 466, 471 (2d Cir.), cert. denied, 429 U.S. 895 (1976), which viewed a similar circumstance as follows: "In situations such as this where the grand jury is focusing its attention upon a series of related acts occurring over a period of time, it is inevitable that its questions will overlap to a certain degree. [See Bursey v. United States, 466 F.2d 1059, 1079 (9th Cir. 1972) (some repetition inevitable, even desirable, if not excessive).] But such overlapping alone is not enough to require that the allegedly false responses of the witness be consolidated into a single perjury count where, as here, each of the critical inquiries was directed to a separate facet of the overall transaction being investigated."

Based on these and other cases, the rule which emerges is a strict one. As a practical matter, it appears that individual lies will only constitute the same perjury, thereby barring multiple convictions, where they involve facts which are "substantially identical." Masinia v. United States, supra. Likewise, close analysis reveals that multiple convictions will be allowed to stand even where the factual difference between the perjuries is slight. In sum, it appears from these cases that convictions for perjury will only be held reversible on the ground of multiplicity where individual falsehoods are "so related . . . [in] subject-matter . . . [and] so linked and blended together in point of time, as to constitute but one act or transaction, and therefore constitute but one offense." Commonwealth v. Davenport, 255 Pa. Super. 131, 146 (1978), quoting State v. Anderson, 35 Utah 496, 503 (1909).

The application of these principles is best illustrated in decisions which vacate one or more convictions on the ground of multiplicity while affirming others as involving distinct perjuries. These cases are set out in the margin. It is significant that the majority of cases find no multiplicity among the convictions. While none of these decisions is dispositive of this case, the general principles stressed therein are not supportive of the defendant's position on the present facts.

B. Putting Aside Jeopardy Arguments About "Lesser Includeds."

The defendant contends that counts 1-3 are, in a factual sense, lesser included charges within count 4. In the defendant's view, the evidence required to prove the first three counts is also required to prove the fourth, and the application of the "same evidence" test would bar multiple punishment. See Commonwealth v. Gallarelli, 372 Mass. 573, 577-579 (1977) (rejecting "same transaction" test). At first glance, these arguments have a certain appeal, particularly in view of the recent emphasis placed on the factual "realities of the offenses" in double jeopardy analyses. Commonwealth v. St. Pierre, 377 Mass. 650, 661-663 (1979), and cases cited. Commonwealth v. Jones, 382 Mass. 387, 393-394 (1981). But see Commonwealth v. Crocker, 384 Mass. 353, 359-361 (1981) (overruling in relevant part Commonwealth v. Cerveny, 373 Mass. 345). On the other hand, the Commonwealth argues that the same evidence test is satisfied because each of the four perjuries involved a new lie about a different period of time. As a result, the Commonwealth maintains that the trial judge could have found the defendant "innocent on one [count] and guilty on the other[s] without creating any . . . conflict." United States v. Tyrone, 451 F.2d 16, 18 (9th Cir. 1971).

In our view, however, both parties are incorrect in their assumption that the same evidence test controls the result in this case. Whatever bearing factual "realities" may have on the analysis, it is now reasonably settled that the test ultimately focuses on the "elements of the statutory offenses charged." Commonwealth v. Crocker, supra at 358. Cepulonis v. Commonwealth, 384 Mass. 495, 501 n. 5 (1981). For that reason, the test has been stated to apply ordinarily only in cases involving "offence[s] against two [different] statutes." Morey v. Commonwealth, 108 Mass. 433, 434 (1871). Kuklis v. Commonwealth, 361 Mass. 302, 306 (1972). Commonwealth v. Gallarelli, supra at 577. Commonwealth v. Crocker, supra at 357. Contrast Gallinaro v. Commonwealth, 362 Mass. 728, 733 (1973).

It appears, then, that the same evidence test "has no application here since a single statute is involved and the issue is whether two [or more] discrete offenses were proved under that statute rather than a single continuing offense." Commonwealth v. Winter, 9 Mass. App. Ct. at 527 n. 16. Cf. Commonwealth v. Levia, 385 Mass. 345, 350 (1982). Rather, the test has itself been viewed as a "rule of statutory construction" which merely aids in answering the "dispositive question," i.e., whether the Legislature intended to authorize multiple convictions in a given situation. Albernaz v. United States, 450 U.S. 333, 337, 344 (1981). See Commonwealth v. Crocker, supra at 359-361, and authorities cited. Since the same evidence test cannot aid us in a case involving a single statute, we look to the statute to determine whether convictions for the four perjuries here comport with the "allowable unit of prosecution" intended by the Legislature for that offense. Bell v. United States, 349 U.S. 81, 81 (1955). See Commonwealth v. Levia, 385 Mass. at 347-348. See also Sanabria v. United States, 437 U.S. 54, 69-70 (1978); Commonwealth v. Winter, supra at 524.

C. Unit of Prosecution Authorized by G.L.c. 268, § 1.

Under G.L.c. 268, § 1, "[t]he crime of perjury in a judicial proceeding occurs whenever one `willfully swears or affirms falsely in a matter material to the issue or point in question.'" Miaskiewicz v. Commonwealth, 380 Mass. 153, 158 (1980), quoting from Commonwealth v. Geromini, 357 Mass. at 63. The quoted portion of the statute has been in its present form since the turn of the century, see R.L.c. 210, § 1 (1902), and statutes punishing perjury as a crime have been in force in this Commonwealth since colonial times. See generally Commonwealth v. Giles, 350 Mass. 102, 105-109 (1966). The penalties permitted under these statutes have consistently been severe, and the present statute is no exception.

The statute manifests a strong legislative policy against perjury in judicial proceedings. The reasons underlying this policy are obvious. Perjury strikes at the heart of our judicial system and constitutes, in fact, "an obstruction of justice," the "perpetration [of which] well may affect the dearest concerns of the parties before a tribunal." United States v. Norris, 300 U.S. 564, 574 (1937). See Bronston v. United States, 409 U.S. 352, 357 (1973). In short, it is elementary that in a system which strives after truth as the predicate for doing justice, nothing is more pernicious than the deliberate introduction of falsehood. Our statute, like its Federal counterpart, was "enacted in an effort to keep the course of justice free from the pollution of perjury." Id., quoting from United States v. Williams, 341 U.S. 58, 68 (1951).

In view of these concerns, the deterrent purpose of the statute, and the severity of the penalties which it provides, we conclude that, where the other elements of the offenses are present, a separate perjury is committed each time a wilful false statement is made, see Commonwealth v. Geromini, supra at 63-64, except where such statements are "substantially identical," Masinia v. United States, 296 F.2d at 880. "[I]nsofar as each count is based on a separate act, i.e., a false answer to a question concerning a different material fact or point, then each count is a distinct offense of perjury as defined by the statute." People v. Guppy, 30 Ill. App.3d 489, 494 (1975) (affirming ten of thirteen convictions for perjury before grand jury over claim that statements constituted a single offense). See Model Penal Code § 208.20, Comment 2, at 115-116 (Tent. Draft No. 6, 1957) (recommending that perjurious "statement" be construed to connote "any single item of information communicated in one sequence of declarations or responses to questioning"). See also State v. LaBarre, 114 Ariz. 440, 442-443 (Ct. App. 1977); Commonwealth v. Davenport, 255 Pa. Super. at 145-146.

Our conclusion is consistent with the result reached in other Massachusetts cases involving multiple convictions for perjury, and with the reasoning of cases dealing with crimes of similar ilk, which hold that separable criminal acts may be punished as discrete offenses rather than as a single transaction. See Commonwealth v. Beal, 314 Mass. 210, 224-227 (1943) (bribery); Commonwealth v. DeVincent, 358 Mass. 592, 594-595 (1971) (attempted extortion); Matter of DeSaulnier (No. 3), 360 Mass. 769, 777-780 (1971), habeas corpus granted sub nom. Baker v. Eisenstadt, 456 F.2d 382, 389-395 (1st Cir.), cert. denied, 409 U.S. 846 (1972) (contempt). See also Commonwealth v. Levia, 385 Mass. at 347-351 (armed robbery while masked).

It is also consistent with the view that where the lies are only broadly related to a particular area of inquiry the Legislature did not intend to punish multiple perjuries as a single offense. "To adopt [that] position would permit witnesses, who lie once, to escape punishment for an unlimited number of additional false statements." People v. Guppy, 30 Ill. App.3d at 494. The sounder rule is that "[t]he commission of perjury as to one matter [should] not absolve the witness or afford him immunity as to all other matters covered by his testimony at the same hearing. The obligation to testify truly and the penalty for false swearing is present as to every material answer given by him." Id. at 493; United States v. Masters, 484 F.2d at 1253. United States v. Cason, 39 F. Supp. 731, 734-735 (W.D. La. 1941). State v. LaBarre, supra at 442 (all quoting from Seymour v. United States, 77 F.2d 577, 581 [8th Cir. 1935]).

Applying these principles, in light of the cases, we conclude that the defendant's convictions for four perjuries must stand. Although it is true that the extended periods involved in counts three and four create some overlap, each count involves a new lie about a period which is separate and distinct from the others. We are satisfied that the four perjuries are not "substantially identical," and that the overlap may properly be treated as immaterial to the result. Cf. Gallinaro v. Commonwealth, 362 Mass. at 732-733; Commonwealth v. Peretz, 212 Mass. 253, 256 (1912).

Finally, we reject the defendant's suggestion that the prosecutor improperly fragmented what might have been a single perjury into multiple separate offenses by the manner in which he asked his questions. The generally broad discretion a prosecutor possesses with respect to examination before a grand jury is limited by the rule that he may not break down an inquiry in order to "run up a possible perjury sentence indefinitely." Gebhard v. United States, 422 F.2d at 290. The fact that some questions overlap will not, standing alone, establish impermissible fragmentation. It is unquestioned that separate prosecutions for each year in which Quincy submitted fraudulent reports would be justified (see Commonwealth v. Cerveny, 373 Mass. at 346-348), and that the defendant's testimony was material to the grand jury's scrutiny of each particular year. Id. at 352. See Commonwealth v. Borans, 379 Mass. at 135. In these circumstances the prosecutor had the right, if not the duty, to pin down the facts of Boynton's employment one year at a time. Indeed, if the prosecutor thought the defendant was likely to perjure himself, detailed inquiry was appropriate since "[p]recise questioning is imperative as a predicate for the offense of perjury." Bronston v. United States, 409 U.S. at 362. Had he continued the inquiry there is no doubt that the defendant could have been convicted on a separate count for each of the six years as to which his testimony was false. In the absence of any indication that the questioning was conducted in bad faith, or indication that the prosecutor called the defendant before the grand jury merely for the purpose of extracting perjuries for which to indict him (see Brown v. United States, 245 F.2d 549, 554-555 [8th Cir. 1957]; contrast Commonwealth v. Borans, supra at 138-139), we see no basis for concluding that the questioning was improperly fragmented.

2. The defendant argues three additional issues, each of which lacks substantial merit.

A. The defendant claims that the trial judge should have excluded certain testimony given by the Commonwealth witnesses Bardon and Vogel on the ground that it was "recently fabricated," and that without this testimony there is no evidence that the defendant's perjuries were wilful and intentional. The fact that these witnesses did not give this testimony before the grand jury more than a year earlier did not establish that the testimony was recently fabricated since there was no showing that they were asked about the matter at that time. Moreover, the doctrine upon which the defendant relies is not a rule which would require the exclusion of the testimony. See Commonwealth v. Zukoski, 370 Mass. 23, 26-27 (1976). See also Liacos, Massachusetts Evidence § 9(D), at 168-169 (5th ed. 1981). Compare Proposed Mass.R.Evid. 801(d) (1) (B) (1980), noted in Liacos, supra § 13(A), at 264. The claim of recent fabrication bore on the credibility of the witnesses and the weight to be given their testimony. The judge "could not properly have . . . [excluded the testimony] on the ground that it was incredible as a matter of law." Commonwealth v. Lewis, 12 Mass. App. Ct. 562, app. 574 (1981).

B. The defendant contends that the Commonwealth violated the pretrial conference agreement, see Mass.R.Crim. P. 11, 378 Mass. 862 (1979), by failing to make timely disclosure of statements made by Bardon and Vogel to the Commonwealth's investigator. The Commonwealth concedes that the agreement required it to disclose written statements of its witnesses, and that the information obtained from Bardon and Vogel was reduced to writing in the investigator's reports, but argues that these reports do not constitute "statement[s]" as defined by Mass.R.Crim.P. 14(d), 378 Mass. 881 (1979). Compare Commonwealth v. Lewinski, 367 Mass. 889, 902 (1975), quoted in Commonwealth v. Borans, supra at 151 (stating prior definition). We do not reach the merits of the Commonwealth's argument, however, since the defendant has failed to show that he was prejudiced by any failure to make timely disclosure of the reports.

The Commonwealth first received the information relevant here from Vogel on a Friday and from Bardon on the following Monday. The trial commenced on Tuesday. Bardon testified on Wednesday, and defense counsel received a copy of the report containing his statements at the conclusion of his direct testimony. Cf. Commonwealth v. Lewinski, supra. Although the judge then offered counsel an opportunity "to defer . . . cross-examination of the witness," apparently until the following morning, counsel read the report and chose to proceed with his examination. Vogel was the next witness. Although counsel apparently did not receive a copy of the report containing her statements prior to cross-examination, the Commonwealth had previously summarized her testimony in its trial brief, which counsel acknowledged receiving. In addition, the substance of Vogel's testimony on the point relevant here was identical to that given by Bardon. On these facts, the defendant has failed to show that he was prejudiced by any violation of the pretrial conference agreement. See Commonwealth v. Gilbert, 377 Mass. 887, 895-896 (1979); Commonwealth v. Cundriff, 382 Mass. 137, 150-151 (1980); Commonwealth v. Spann, 383 Mass. 142, 149-150 (1981).

C. The defendant argues that the thirteen days which elapsed between the end of the trial and the formal entry of the guilty findings manifests that the judge harbored uncertainty inconsistent with findings of guilt beyond a reasonable doubt. On the first day following the trial, however, the judge reported to counsel that he had reviewed the evidence and was "satisfied beyond a reasonable doubt that there has been perjury" as charged. The judge then continued the case for the express purpose of considering, and allowing the parties to research, the question of multiplicity. It is quite clear from the transcript that defense counsel understood the posture of the case at that time and in several subsequent hearings. We are satisfied that the judge harbored no uncertainty as to the defendant's guilt beyond a reasonable doubt.

Judgments affirmed.