The defendant appeals from his conviction, after a jury trial in the Superior Court, of conspiracy to commit automotive insurance fraud, in violation of G. L. c. 266, § 11 IB. Specifically, he complains that (1) the judge erred when he denied the defendant’s motion for a required finding of not guilty; (2) the judge should have given a specific unanimity instruction; (3) the Commonwealth’s expert overstepped the proper bounds of expert testimony; and (4) there was prosecutorial error in the Commonwealth’s closing argument. We affirm.
Background. We recite the facts in the light most favorable to the Commonwealth. Some facts are reserved for discussion of the issues. The defendant, an attorney with a busy personal injury practice, was accused of agreeing to participate in submitting fraudulent insurance claims. The law office was very busy, taking in fifty to seventy-five new clients every week. More than ninety-five percent of the cases involved “auto claims,” and these clients were all “referred by someone.” It seemed that only the defendant’s office manager, Josefina Diaz, was allowed to speak to the people referring clients, and on Mondays and Wednesdays, she made cash payments to the “referrers,” but only after she met with the defendant in his office. Diaz kept a notebook of the referrals that other people in the office were prohibited to open or examine.
Carlos Finales participated in and staged collisions. Finales became interested in referring clients to the defendant, and sometime prior to June 3, 2003, he approached the defendant alighting from his vehicle outside his law office. Finales, who was unknown to the defendant, told the defendant that he could “bring him clients.” Without further discussion, the defendant directed Finales to Diaz, who arranged a referral payment of $150 per client that Finales brought in.
On June 3, 2003, Finales brought three men who allegedly were injured in an automobile accident (Efxain Palma, Melvin Morales, and Nelson Valdera) to the defendant’s law office.1 The three men met first with an intake secretary who brought them individually to an associate attorney, Deborah Cuomo, who worked for the defendant. Thereafter, consistent with the arrangement *568made with Diaz, Piñales was paid $150 for each of these referrals.2 The purported accident victims testified that they never met or spoke with the defendant. In addition, Piñales admitted that he never told the defendant that this or any other accident had been staged or was fraudulent, although he testified that it was in fact staged.
Piñales testified that every Monday for about three or four months in 2003, he went to the defendant’s office around 4:30 or 5:00 p.m. to collect his money. Although Diaz would distribute the cash, payment always required the defendant’s presence in the office. Sometimes, Piñales saw other friends of his who were involved in staging accidents also waiting at the defendant’s law office.
In September of 2003, a woman died in a staged accident in Lawrence. This “accident” drew significant media attention, and by early 2004, the police had made a number of arrests. In either January or February, 2004, the police attempted to speak with the defendant at his law office; they were told to leave. The next day, the defendant called the Lawrence police department asking to speak to the chief of police, John Romero. Romero suggested that the defendant make an appointment, but the defendant insisted on seeing him immediately. After the defendant arrived at the police station, he asked Romero to accompany him on a walk. Romero insisted that they speak in his office and the defendant was reluctant, fearing the conversation would be “taped.” Romero responded, “[Y]ou as an attorney know we can’t do that.”
In Romero’s office, the defendant, who was nervous, said, “I know you are conducting an investigation of my office .... I know it is going on. ... I didn’t do anything wrong. . . . [W]hat if I was willing to close my practice and give up my license, would this stop[?]” When asked why he would do that, the defendant then said, “What if I told you I paid runnersf?]”
1. Sufficiency of the evidence. The defendant was charged with conspiracy, a crime prohibited by G. L. c. 274, § 7. While no definition of conspiracy is provided by statute, a definition exists at common law: conspiracy is a “combination of two or *569more persons, by some concerted action, to accomplish some criminal or unlawful purpose.” Commonwealth v. Beneficial Fin. Co., 360 Mass. 188, 249 (1971), cert. denied, 407 Mass. 910, 914 (1972), quoting from Commonwealth v. Hunt, 4 Met. 111, 123 (1842).
The Commonwealth offered sufficient evidence to show the defendant’s knowledge of, and agreement with, a fraudulent scheme. The Commonwealth concedes that there was no direct evidence from the defendant or from Piñales that they expressly had agreed to submit false insurance claims; indeed, there was evidence of only one meeting between the defendant and Piña-les, during which Piñales said, “[H]e could bring [the defendant] clients.” The defendant did not converse with Piñales, merely telling him to see Diaz, his office manager.
The Commonwealth is not limited, however, to direct evidence. “A conspiracy may be proved by circumstantial evidence, and this is the usual mode of proving it, since it is not often that direct evidence can be had. The acts of different persons who are shown to have known each other, or to have been in communication with each other, directed towards the accomplishment of the same object. . . may be satisfactory proof of a conspiracy.” Commonwealth v. Pratt, 407 Mass. 647, 653 (1990), quoting from Commonwealth v. Smith, 163 Mass. 411, 417-418 (1895). See Commonwealth v. Nelson, 370 Mass. 192, 196-197 (1976) (to conclude that “a person who joined a conspiracy to ‘fix’ a horse race, but who limited his participation to supplying the funds to be used in the scheme, and who scrupulously avoided acquiring knowledge of the method and means by which his coconspirators planned to alter the outcome of the race, could not be found guilty of conspiracy ... is not in accordance with the existing law”).
Particularly persuasive in support of the verdict was the evidence of what occurred following news concerning a “staged” accident that resulted in a fatality. The accident involved neither the defendant nor Piñales. Diaz, implicitly acting upon the defendant’s instructions, called Piñales to say that he was to “come and get [his] clients” for whom he had not been paid, to take them “somewhere else,” and not to bring any new clients.
The evidence of what transpired during a meeting between *570the Lawrence police chief and the defendant also supports a conviction. The defendant, while maintaining his innocence, offered to give up his license to practice law in exchange for the police stopping an investigation regarding the defendant’s office; when the chief asked why he would do so, the defendant said, “What if I told you I paid runners[?]” See Commonwealth v. MacLeod, 9 Mass. App. Ct. 934, 935 (1980) (offer to “make a deal” with police evidence of consciousness of guilt). While the defendant contends that this evidence suggests only consciousness of guilt about his breach of legal ethics, it was also probative of a guilty conscience about criminal acts because he likely would know that the police do not investigate violations of the rules of professional conduct.
In addition, there was evidence that (1) the defendant’s secretaries were told that only Diaz was permitted to speak with Piñales and others who came into the office having “referred” clients; (2) Diaz kept a book that other office staff were forbidden to examine, in which she entered names of clients and those who had referred them, and in which she noted referral payments; (3) Piñales and others came for their payments only on certain assigned afternoons, and although he and others were paid by Diaz, she only could do so when the defendant was in the office and after checking with him; (4) the payments were always in cash and never by check; and (5) reports from the same chiropractic office regarding the three clients from the June 3, 2003, “accident” were sent to the defendant and described the effects of the accident on each in almost identical terms.
In our review for sufficiency of the evidence, we consider the evidence in the light most favorable to the Commonwealth along with any reasonable inferences drawn therefrom. Commonwealth v. Latimore, 378 Mass. 671, 676-677 (1979). While each factor by itself likely would not be enough to support conviction, our review for sufficiency leads us to conclude that these circumstances present sufficient evidence of knowledge and agreement to participate in submitting false claims to an insurance company for a rational jury to find the defendant’s guilt beyond a reasonable doubt.
2. Specific unanimity instruction.3 The defendant contends *571that the judge erroneously declined to instruct the jury that it would have to be in unanimous agreement as to the particular coconspirator (or coconspirators) with whom the defendant unlawfully had conspired. We find that there was no error, as the law does not require such an instruction.
Jury verdicts in criminal cases “must be unanimous,” and in certain narrowly defined circumstances, a general unanimity instruction is insufficient “to ensure the requisite unanimity.” Commonwealth v. Santos, 440 Mass. 281, 284 (2003). Generally, a defendant is entitled to a specific unanimity instruction only “when the Commonwealth has proceeded on ‘alternate theories’ ” of guilt, defined as “separate, distinct, and essentially unrelated ways in which the same crime can be committed.” Id. at 287-288. The law does not require that “the jury must be unanimous in their parsing of the details as to how a crime was committed.” Id. at 289, citing Commonwealth v. Laurore, 437 Mass. 65, 82 (2002), and Commonwealth v. Cyr, 433 Mass. 617, 623 (2001).
While it may be necessary in some circumstances to give a specific unanimity instruction when the indictment is capable of incorporating multiple incidents or theories, the defendant’s argument that multiple coconspirators are the legal equivalent of multiple theories is not a correct statement of the law. “No unanimity instruction was required because a conspiracy refers to a continuing course of conduct, rather than a succession of clearly detached incidents.” Commonwealth v. Albert, 51 Mass. App. Ct. 377, 385 (2001), citing Commonwealth v. Cerveny, 387 Mass. 280, 288 (1982). Similarly, here, the Commonwealth alleged in a single indictment that the defendant was involved with Piñales and others in only one conspiracy: to commit insurance fraud. The bill of particulars first narrows the time period to coincide with the point in time from which Piñales brought Palma, Morales, and Valdera to the defendant and, second, refers only to the June 3, 2003, accident, specifically, as fraud*572ulent. So long as the Commonwealth was able to prove that the defendant was involved with at least one other person in an unlawful agreement, a conspiracy existed.
Specifically, the Commonwealth alleged, particularized, and tried the defendant on the basis that he, and others in his office, were engaged in a plan to commit insurance fraud with Piñales. That Diaz and Cuomo were acquitted when the judge allowed their motions for a required finding of not guilty does not alter the analysis, because the theory of the government’s case never was that the defendant was engaged with others on his staff to the exclusion of Piñales. There can be no risk that any juror concluded that the defendant conspired with Cuomo or Diaz, but not with Piñales, because the entire fraudulent scheme depended on Piñales.
Moreover, the judge instructed the jury that “[t]he Commonwealth must prove beyond a reasonable doubt that [the defendant] joined Ms. Cuomo, Ms. Diaz and/or Mr. Piñales in a plan collectively to commit motor vehicle insurance fraud, that is to say that he joined one or more of them in a plan, collectively to do those things which constituted motor vehicle insurance fraud. The plan that must be proven is not that each participant in the plan would do all of the acts that constitute motor vehicle insurance fraud but rather that the actions [of] all of them taken together would amount to a motor vehicle insurance fraud as I have defined it.” This instruction illustrates that within a single conspiracy there may be subagreements; “[b]ecause one conspiracy may have many illegal objectives, it will necessarily involve a number of sub-agreements to commit each of these specified objectives. ... If each stitch in that web were treated as a separate conspiracy, infinite bases for liability could be confected.” Commonwealth v. Winter, 9 Mass. App. Ct. 512, 526 (1980), quoting from United States v. Rodriguez, 585 F.2d 1234, 1250 (5th Cir. 1978), afPd, 450 U.S. 333 (1981).
An instruction on specific unanimity such as the defendant requests here would be contrary to the requirements of the law of conspiracy, in effect calling upon the prosecution to prove beyond a reasonable doubt and to the unanimous satisfaction of the jury not only the required elements of the offense, but each subagreement that may have existed. Indeed, as the judge instructed, the Commonwealth “is not required to prove that they agreed on *573every detail of the plan . . . [or] that they ever actually met together or that they even knew the identity of each other” so long as “there was a joint plan among them and ... the defendant adopted that plan, knowing that others were part of it.” That Diaz and Cuomo were acquitted by judicial order does not alter the analysis, because there was only a single conspiracy alleged, even if it may have been dependent on a web of interconnected actions by and between others. “[W]hen the plot contemplates bringing to pass a continuous result that will not continue without the continuous cooperation of the conspirators to keep it up, and there is such continuous cooperation, it is a perversion of natural thought and of natural language to call such continuous cooperation a cinematographic series of distinct conspiracies, rather than to call it a single one.” Commonwealth v. Winter, supra at 527, quoting from United States v. Kissel, 218 U.S. 601, 607 (1910).
As noted previously, there was no potential for jury confusion. The Commonwealth’s case depended upon Finales as the linchpin, without whom no clients would have been brought to the defendant’s office and thus no unlawful purpose would have been accomplished. The principles of specific unanimity do not apply on the facts of this case.
3. Expert testimony. The defendant contends that Kimberly Giardina, the Commonwealth’s first witness, improperly was allowed to give expert opinion testimony about “runners.” He complains that she was permitted to opine on the defendant’s guilt when “[s]he essentially said that everyone ‘on the street’ who dealt with a runner knew that the referred cases were staged,” implying that the defendant would have known that Finales was a runner, i.e., a person who brought fraudulent accident clients to lawyers.
First, although the defendant had filed a motion in limine concerning this testimony, which he renewed at the beginning of the witness’s testimony, he did not preserve the issue for appellate review by a contemporaneous objection to the testimony. Commonwealth v. Gaynor, 73 Mass. App. Ct. 71, 76 (2008). The only objections that he made during her direct testimony about runners were to two nonresponsive answers. (Full quotations from the trial testimony of the witness, concerning “runners,” are set forth in the Appendix to this opinion.) Therefore, we examine this claim under the standard for unpreserved error, to determine *574whether the error, if any, created a substantial risk of a miscarriage of justice.
An expert witness clearly may not “offer an opinion as to the defendant’s innocence or guilt” but may provide opinion testimony about general practices of fraudulent accident claim rings. See Commonwealth v. Woods, 419 Mass. 366, 375 (1995). As the defendant concedes, and upon examination of the expert’s testimony, we are satisfied that her testimony about the operation of fraudulent accident claim rings, specifically, how they are organized and function, was within the proper scope of expert testimony. Moreover, her testimony did not link or relate her opinions to particular defendants herein.
Next, contrary to the defendant’s specific complaints, examination of the transcript4 reveals that the witness did not testify, as *575claimed by the defendant, (1) “that the term ‘runner’ was used ‘on the street’ to refer to persons who only staged accidents”5 ; (2) that “by definition all ‘runners’ are persons who stage accidents”6; or (3) “that such runners do not ever refer legitimate cases to attorneys.”7
Nonetheless we think the witness should not have been allowed to define the term “runner” without a proper foundation demonstrating that her definition was accepted in the relevant community. See Canavan’s Case, 432 Mass. 304, 313-315 (2000). See also Mass. G. Evid. § 702 (2008-2009). She personally equated the term “runner” with accident staging and testified that when a “runner” brought legitimate claims to a lawyer, he was not acting in his “runner” capacity. Without the proper foundation, the manner in which she described a “runner” was not a definition but rather a characterization which should have been allowed only if its probative value was not substantially outweighed by danger of unfair prejudice. Id. at § 402, 403. While not specifically argued, this description of the term “runner” was the only explanation given to the jury; we think the potential danger was that the jury would impose this characterization on others’ use of the word. Its potential impact would be particularly troublesome if the jury had applied this characterization to the defendant’s question to Romero, the Lawrence police chief and the last of the Commonwealth’s witnesses, asking, “What if I told you I paid runners[?]”
A judge has broad discretion regarding the admission of expert testimony, and we review that decision only for abuse of discretion. Commonwealth v. Patterson, 445 Mass. 626, 639 (2005). The judge acts as a gatekeeper to all expert testimony, Commonwealth v. Lanigan, 419 Mass. 15, 25-26 (1994), not just that expressing views on scientific matters. Canavan’s Case, supra at 313.
*576We obviously cannot expect the judge to have foreseen how the testimony from several witnesses might intersect. We note, however, that the trial judge had particular experience with this expert and with Piñales from a prior trial. Indeed, the judge intervened during Piñales’s testimony when he answered questions about how he got paid and as he began to describe the scene at the defendant’s law office on Monday afternoons. Just when Piñales was about to start naming other people he recognized who were also in the waiting room, presuming they also were waiting for payment, counsel sought a sidebar conference. At sidebar, the judge was concerned about the direction of this testimony because Piñales did not have personal knowledge of why those other people were present at the law office. The judge did not permit Piñales to call them “runners” after the defendant’s attorney expressly pointed to the expert’s characterization of runners at the sidebar conference.8 Moreover, we note that the prosecutor asserted in his closing that Piñales, whom “we all know is a runner, . . . stag[ed] accidents, and he was doing that for money.”
While no one ever objected to the expert’s characterization of *577the term “runner,” the transcript reveals that the judge was concerned about her testimony, interrupting her for clarification. Given the expert’s idiosyncratic use of this term, in the exercise of the judge’s discretion, a better course would have been to exclude it. Here, however, in the absence of objection, and because neither the expert in her testimony, nor the Commonwealth in its closing, connected or sought to impose the expert’s characterization on the defendant’s use of the term “runner,” while we consider the question close, there was no risk of a miscarriage of justice.9
4. Prosecutor’s closing argument. The defendant complains that the prosecutor improperly invited the jury to think that they could convict on less evidence than necessary by saying the “less said the better,” and that his “cash cow” extrapolation was overly prejudicial to the defendant even though the judge immediately gave a direct and forceful curative instruction. We disagree.
As to the first claim, the defendant’s failure to provide adequate argument and authority need not detain us longer than to simply observe that when the prosecutor made reference to the “less said the better,” he merely was expressing his theory, based on the evidence, that the defendant sought to maintain deniability by avoiding discussion among him and his coconspirators. There was no suggestion on the prosecutor’s part that the jury could convict on less than adequate evidence.
As far as the “cash cow” extrapolation argument is concerned, the jury is presumed to follow judicial instructions, and here, the judge’s prompt, direct, and forceful curative instructions were sufficient to address this particular occasion of prosecuto-rial overreaching. There was no error.
Judgment affirmed.
Appendix.
The following, in pertinent part, are quotations from the transcript of the expert’s testimony concerning her characterization of the term “runner.”
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Diaz’s trial counsel first objects, which, when coupled with the next objection, and considering the response given to this short line of questions, clearly was being made on responsiveness grounds. The prosecutor then began a new line of examination, calling for explanation of the various ways that accidents can be “staged,” how the claim is submitted, and how the runner is paid.
On cross-examination, trial counsel for the defendant brought out the following additional testimony about runners and Piñales:
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Pinales, Palma, and Morales later became cooperating Commonwealth witnesses and testified against the defendant.
Both Diaz and Cuomo were indicted for conspiracy with the defendant, but their motions for a required finding of not guilty were successful.
Within this argument, the defendant contends also that the judge conflated *571the principles of joint venture in his instructions to the jury on the substantive law of conspiracy. Even if we were to consider the issue as adequately briefed under the provisions of Mass.R.A.P. 16(a)(4), as amended, 367 Mass. 921 (1975), which it was not, the judge’s instructions were substantially similar to the defendant’s own requested jury instructions on this point, and he did not preserve the issue by objecting to the instruction.
Her testimony on this subject began as follows. We set forth below, in part, and more fully in the Appendix, the transcript of the expert’s testimony regarding the term “runner.”
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The witness used the phrase “on the street” to refer to “cases,” not to runners.
She testified that she defined the term “runner” as a person who stages accidents, not that her definition was the commonly understood meaning of the term.
While by the witness’s estimation, the term “runner” does not apply to people who bring legitimate claimants to chiropractors and to law offices, she admitted that “the same person on one case with the staged collision [could] act as a runner in which they’ve staged a collision and [could] act as someone who is just referring individuals with respect to a legitimate accident.”
Cuomo’s counsel: “We’re pre-objecting to that since it will probably come out quickly.”
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Indeed, the point is sufficiently subtle that the defendant has not argued it in his brief, further suggesting that it was unlikely to have influenced the jury.