The defendant, a psychiatrist, was convicted by a Superior Court jury of two counts of larceny over $250 in violation of G. L. c. 266, § 30, and 219 counts of Medicaid fraud in violation of G. L. c. 118E, § 40. The fraud counts were of two types: (1) billing and receiving payment for services which could not have been performed because he was on vacation; and (2) billing and receiving payment for services performed on days for which, adding together the times required for the services allegedly performed, the billings represented more than twenty-four hours of services.1 The sentences imposed included one year of jail time that was stayed pending appeal.

1. Publicity. On the morning of the second day of jury deliberations, the Boston Herald printed an article about the trial, including references to extravagant spending by the defendant. When jurors began arriving at the courthouse that morning, neither a court reporter nor the parties were present. The judge stationed himself to catch the jurors as they arrived and asked them individually if they had read the article. Each juror responded in the negative. The judge took the Boston Herald from the several jurors who had it and noted (later, in the courtroom) that, based on the condition of the papers, he *536believed that they had not been read. (The article began on page ten of the newspaper.) Using scissors, the judge clipped out the article. He then instructed each juror that he or she was not to consider any kind of extraneous sources. Once all the parties had arrived, the judge called the jury to the courtroom. He gave the jurors a strong instruction to disregard anything they might hear outside the evidence in the case, and directed them to resume deliberations. After the jury retired, the judge described his contact with jurors and his being satisfied that none of the jurors had read the article. The judge then denied the defendant’s request for a more detailed, on the record, questioning of the jurors.

“When a judge conducts an inquiry about a consequential matter . . . there is a requirement, deriving from the constitutional rights of confrontation and fair trial, that the defendant and his counsel be present.” Commonwealth v. Martino, 412 Mass. 267, 286 (1992), and cases cited. “The absence of the defendant from such a colloquy, however, does not automatically constitute reversible error.” Ibid. We cannot fault the judge for taking vigorous preventive action while he could do so, at a time when neither the court reporter nor the parties were available in the courthouse. By immediate action it was possible to avoid or minimize the impact of the article. Given the unusual circumstances, and because the judge reported that “every single juror assured me that they had not read the newspaper,” the judge’s private communication with the jurors was harmless beyond a reasonable doubt. Compare Commonwealth v. Hicks, 22 Mass. App. Ct. 139, 147 (1986) (judge dismissed all three jurors who admitted reading newspaper article).

Once all the parties were present, the judge put the details of his communications with the jury on the record. The judge did not err by refusing to replicate his inquiry of the jurors on the record. The jurors individually had already assured the judge that they had not read the Boston Herald that morning, and the judge had a right to rely on those responses. Compare Commonwealth v. Palmariello, 392 Mass. 126, 142 (1984); Commonwealth v. Ali, 43 Mass. App. Ct. 549, 564-565 (1997). The judge had acted commendably to prevent the taint from reach*537ing the jurors; he could reasonably regard further inquiry as needlessly time-consuming. Compare Commonwealth v. Francis, 432 Mass. 353, 371 (2000). Nor was the judge required to accede to the defense request that counsel be allowed to interrogate the jurors, presumably under oath, concerning when and where they had bought their papers and the sequence of their actions prior to their arrival at the courthouse. Such an examination might have been required if the judge had evidence of wrongdoing or bias, see G. L. c. 234, § 28, but it was not required here. Compare Commonwealth v. Farnkoff, 16 Mass. App. Ct. 433, 438-439 (1983).2

2. Summary charts. The defendant was a provider under both the Medicaid program administered by the Division of Medical Assistance (division) and Medicaid’s mental health and substance abuse program administered by Mental Health Management of America (MHMA). To receive payment for services rendered under these programs, the defendant submitted forms containing the treatment date and a five-digit procedural code indicating the service performed and the amount to be paid. These procedural codes, also known as service codes, were first created by the American Medical Association and published in the Current Procedure Terminology (CPT) manual. The Medicaid program and MHMA also issued definitions of the applicable procedural codes which on occasion varied from the CPT descriptions. As a provider, the defendant agreed to *538abide by all the laws, rules, and regulations applicable to both the Medicaid program and MHMA.

The defendant asserts that the trial judge abused his discretion when he admitted in evidence, over objection, several charts summarizing the Medicaid payments received by the defendant. Two of the challenged exhibits, nos. 31 and 34, were computer printouts containing various information about the defendant’s Medicaid payments, including the service codes billed by the defendant on each treatment day, the time allegedly required to perform that service under applicable regulations, and the amount paid to the defendant. Exhibit 31 also broke out the amount the defendant was allegedly overpaid by Medicaid on each treatment day. Exhibits 33A and 33 listed the time assignments used in exhibits 31 and 34, respectively. The Commonwealth used these exhibits to illustrate the amount of time the defendant would have had to work each day to justify his Medicaid payments.

The defendant complains that exhibits 31 and 34 overestimated the time required to perform certain procedures and therefore misled the jury. “Summary charts of voluminous evidence are permissible if they are accurate and fair, although ‘care must be taken to insure that summaries accurately reflect the contents of the underlying documents and do not function as pedagogical devices that unfairly emphasize part of the proponent’s proof.’ ” Welch v. Keene Corp., 31 Mass. App. Ct. 157, 165-166 (1991), quoting from United States v. Drougas, 748 F.2d 8, 25 (1st Cir. 1984). As the Attorney General’s Medicaid fraud control unit investigator, Anthony Megathlin, who prepared the exhibits, testified, the times in exhibit 31 were based on either the MHMA regulations or the division manual, both of which were entered in evidence. In response to defense counsel’s suggestion that some of the times used in exhibit 31 differed from the times contained in the CPT standards, the investigator created exhibit 34, which showed the hours the defendant would have had to work under the CPT standards. That some evidence in the record contradicted certain time assignments in both exhibits did not render the printouts inadmissible. Defense counsel vigorously cross-examined the investigator about the discrepancies between the times used in *539exhibits 31 and 34 and the terms of the defendant’s contract with Medicaid. See United States v. Sorrentino, 726 F.2d 876, 884 (1st Cir. 1984) (summary admissible where calculations based on admitted evidence and “agent who prepared the chart was available for cross-examination concerning disputed items”). The investigator acknowledged that although he assigned thirty minutes to many of the claims for pharmacological management, coded 90862 in the printouts, neither the MHMA regulations nor the defendant’s contract imposed any minimum time limit to that code. The defendant’s assertion that the printouts overestimated the time required to perform the services billed went to the weight and credibility of the Commonwealth’s summaries, not to their admissibility. See United States v. Nivica, 887 F.2d 1110, 1125 (1st Cir. 1989) (arguments regarding the inadequacies of summaries “go to the completeness of the underlying documents, affecting the weight rather than the admissibility of the government’s summaries”), cert, denied, 494 U.S. 1005 (1990).3

The same was true of “exhibit X,” a thirty-four page bar chart depicting the hours the defendant billed Medicaid each day from March 15, 1993, to December 15, 1995, which was used as a chalk at trial. “A judge . . . has ‘considerable, but not unrestrained, discretion as to the degree to which chalks can be used.’ ” Commonwealth v. DiFonzo, 31 Mass. App. Ct. 921, 923 (1991), quoting from Commonwealth v. Walter, 10 Mass. App. Ct. 255, 264 (1980). Exhibit X assembled data from claims submitted by the defendant and from remittance advice forms received by the defendant. While the defendant did not see the chalk until the first day of trial, he had sufficient access to the underlying information prior to trial. Defense counsel effectively highlighted the chalk’s inaccuracies during cross-examination.

Likewise, the judge’s ruling that Megathlin was qualified to testify about the hours and overpayment calculations in the *540summary charts was proper. As noted above, Megathlin’s time assignments were based on MHMA and division regulations and CPT code standards. Any ambiguities regarding these calculations presented an issue of weight and credibility for the jury, rather than an issue of admissibility. See Doherty v. Belmont, 396 Mass. 271, 276 (1985).

3. Limitation of cross-examination. The defendant complains that the judge committed reversible error by limiting defense counsel’s cross-examination of Megathlin concerning his overpayment calculation. On direct examination, Megathlin was allowed to testify that, by his calculation, the defendant received $180,000 in overpayments from Medicaid. The calculation assumed that the defendant saw a limited number of patients for the full time required under the procedural code billed and did not see the remaining patients billed to the same day. That is to say, Megathlin totaled the time required to provide each procedure billed on a particular day until he reached fourteen hours’ worth of the defendant’s services. Any payments received by the defendant for procedures performed on other patients after this fourteen-hour limit were treated as overpayments. (The chart seems to have been geared to the counts originally presented, before the prosecutor agreed to limit the proof to the counts representing time in excess of twenty-four hours per day. See note 1, supra.)

On cross-examination, defense counsel attempted to show that Megathlin’s overpayment calculation was inflated by asking him to recalculate what the overpayment would be if, as the defendant contended, the defendant rendered services to all of the patients billed for but mistakenly billed under a more expensive procedural code than the time spent warranted.4 The Commonwealth objected and the judge excluded that line of inquiry.

“[Ajlthough the defendant [was] entitled to a reasonable *541cross-examination of the witnesses, the scope of the cross-examination rest[ed] largely in the sound discretion of the trial judge.” Commonwealth v. Montez, 45 Mass. App. Ct. 802, 810 (1998), citing Commonwealth v. Daye, 411 Mass. 719, 735 (1992). Here, defense counsel cross-examined Megathlin extensively about mistakes made in his summary charts and ambiguities in the time requirements assigned to the codes used by the defendant. Defense counsel elicited from Megathlin that the defendant could have seen all of the patients billed on a particular day and, under such circumstances, would have been entitled to reimbursement under a lower paid procedural code. Recalculated in that manner, defense counsel argued, the column shown as overpayment would be sharply reduced.

The trial judge excluded the line of inquiry calling for Megathlin to do the recalculation. The judge’s position was that the defendant, by using the billing codes he did, represented that he spent the time with the patient so billed; the judge refused to allow speculation as to the amount of the overpayments based on the use of other codes. Had matters been left there, we would be concerned that the judge had foreclosed a line of inquiry that had grounding in the evidence: namely, that the defendant in fact saw all the patients he billed for but billed them on a code that represented more time than was actually spent. As the lengthy trial progressed, however, the judge allowed the defense to make exactly the same point in its cross-examination of another witness, Robert Russo, another investigator assigned to the Medicaid fraud control unit of the Attorney General’s office. Through him the defense brought out that the recalculation would bring the overpayment down to $73,000, a figure that Russo agreed represented less than five per cent5 of the $1.3 million the defendant had billed in the three-year period covered by the indictments.

Since the information sought of Megathlin came in through Russo, the defendant’s right of cross-examination was not infringed. Contrary to the defendant’s assertion, the judge’s subsequent instruction to the jury to disregard defense counsel’s statements regarding the damage calculations in his closing did not preclude the jury from considering Russo’s testimony. The *542point of the judge’s instruction was that the jury’s function was not to determine damages but simply to determine whether the defendant billed for services in excess of those performed.

4. Withhold order. In February, 1996, the division imposed a withhold order on payments to the defendant for further services rendered to his Medicaid patients. The defendant claims the judge erred in allowing in evidence copies of the withhold notification letter and applicable State regulations. It was the defendant, however, who sought to show the withholding, which ultimately amounted to $238,000, both to suggest that the defendant, by continuing to serve his Medicaid patients for fifteen months without compensation, had already more than repaid the maximum amount the investigators determined to have been overcharged, and to question the defendant’s former wife about the withheld funds to show bias. The judge, in the exercise of his discretion, properly admitted the withhold notification letter and the applicable State regulations to clarify for the jury the circumstances surrounding the withholding. Moreover, it was clear from the text of the notification letter that it did not represent a final determination of the defendant’s culpability by any State agency. Contrast Gram v. Liberty Mut. Ins. Co., 384 Mass. 659, 673 n.11 (1981). The judge instructed the jury, moreover, that “you may draw[] no adverse inferences towards the defendant because of the withhold.”6

5. Kandimalla evidence. The judge did not err in excluding from evidence hospital discharge cards received by and claim forms created by Seetha Kandimalla, one of the defendant’s former secretaries. General Laws c. 233, § 78, provides that a court may, in its discretion, require, as a condition to admissibility of business records, that the party offering the evidence call as a witness one who has personal knowledge of the facts stated in the records. Burns v. Combined Ins. Co., 6 Mass. App. Ct. 86, 92 (1978). See also Sellew v. Tuttle’s Millinery, Inc., 319 Mass. 368, 371 n.1 (1946). The excluded hospital cards were received from the defendant by Kandimalla and then used *543by Kandimalla to create claim forms. Kandimalla did not, however, testify at trial. Instead, the defendant attempted to introduce the hospital cards and claim forms prepared by Kandimalla through another secretary who neither received the disputed cards from the doctor nor created the claim records. Without Kandimalla to authenticate the disputed documents, it was within the judge’s discretion to exclude them. See Burns v. Combined Ins. Co., supra.

6. Evidence of motive. Over the defendant’s objection, the judge admitted evidence of the defendant’s personal expenditures, including evidence that during the time of the alleged overbilling, the defendant spent over $247,000 in credit card purchases, bought expensive clothing, and owned three luxury automobiles. It was not an abuse of discretion to deem that evidence relevant to the Commonwealth’s theory that the defendant defrauded the Medicaid program in order to support his wealthy lifestyle. See Commonwealth v. Burns, 49 Mass. App. Ct. 677, 684 (2000), quoting from Commonwealth v. Ashley, 427 Mass. 620, 624-625 (1998) (“Determination of the weight of [motive] evidence is for the jury, and evidence which merely suggests rather than ‘clearly shows’ a motive for the crime may still be ruled admissible. There is no requirement that evidence [of motive] be conclusive in order to be admissible”). See also Commonwealth v. Jacobson, 19 Mass. App. Ct. 666, 680 (1985). Any prejudice to the defendant caused by the expenditure evidence was minimized by the judge’s exclusion of the most inflammatory items and by his instruction to the jury “to draw no adverse inferences against [the defendant] with respect to spending a lot of money on credit card charges but, rather, only focus [] on the limited issue of motive.” See Commonwealth v. Conkey, 430 Mass. 139, 145 (1999). There was no error.

7. Testimony regarding State regulations. The defendant argues that the judge erred by allowing Commonwealth witnesses to testify as to whether certain hypothetical conduct would violate particular State regulations.7 While the question is close, we think that the judge, acting in his discretion, could *544properly regard the questions as ones exploring how the regulatory authorities interpreted their enforcement roles. The defendant’s counsel were particularly effective in bringing out in cross-examination how the authorities were misinterpreting certain regulations and were overlooking differences in the requirements of the regulations depending on the procedural code used. As to the point most strenuously argued, that the witnesses were allowed in effect to testify that the defendant had violated the regulations, the judge specifically instructed the jury that “[y]ou, the jury, will decide whether or not ... the defendant in this case violated any one of these regulations .... That will be a question that only you, the jury, can say.”8 ******8 The judge’s clear and immediate instruction dispelled any risk of harm to the defendant and there was no error.

8. Willful blindness instruction. A willful blindness instruction is appropriate when (1) “a defendant claims a lack of knowledge,” (2) “the facts suggest a conscious course of deliberate ignorance, and” (3) “the instruction, taken as a whole, cannot be misunderstood [by a juror] as mandating an inference of knowledge” (citation omitted). United States v. Hogan, 861 F.2d 312, 316 (1st Cir. 1988). Contrary to the defendant’s claim, there was sufficient evidentiary basis for the judge’s willful *545blindness instruction.9 Experts in psychiatry testified that psychiatry is a time-oriented specialty and that psychiatrists, such as the defendant, receive significant instruction on the time required to perform various services. As a Medicaid provider, the defendant received the division’s manual and additional written communications describing the treatment associated with each procedural code. The manual contained billing instmctions and directed providers with billing related questions to contact the program’s fiscal intermediary. Moreover, the defendant had personal experience billing, as he prepared and submitted his own Medicaid reimbursement claims during the first six months of his private practice.

Despite the need for accurate billing records, the evidence established that the defendant hired secretaries with no prior billing experience. Former secretaries of the defendant testified that the defendant taught them how to bill and that they received all of the billing information, including the particular code to be billed, from the defendant. Although the defendant received all of the remittances and payments from Medicaid, he never *546directed his secretaries to correct payments for services he did not perform, such as those supposedly rendered while he was on vacation. See United States v. Nivica, 887 F.2d 1110, 1114 (1st Cir. 1989) (“[g]uilty knowledge may be inferred where instances of fraud are repeatedly brought to a defendant’s attention without prompting alteration of his facilitative conduct”). The evidence indicating that the defendant deliberately closed his eyes to the fact that he was overcharging the Medicaid program was sufficient to support the willful blindness instruction.

The judge consistently instructed the jury that they “may” draw an inference of knowledge, see United States v. Cassiere, 4 F.3d 1006, 1024 (1st Cir. 1993), and that neither negligence, error, nor mistake constituted a proper basis for finding knowledge. We discern no risk that jurors believed that the judge’s instruction mandated that they find willful blindness. See United States v. St. Michael’s Credit Union, 880 F.2d 579, 585 n.1 (1st Cir. 1989). Contrast United States v. Littlefield, 840 F.2d 143, 148 n.3 (1st Cir.) (the danger of an improper willful blindness instruction is “the possibility that the jury will be led to employ a negligence standard and convict a defendant on the impermissible ground that he should have known [an illegal act] was taking place”) (citation omitted), cert, denied, 488 U.S. 860 (1988).

9. Discharge of a deliberating juror. During deliberations, the judge learned that the son of one of the jurors had alleged that the juror had a grievance against the Commonwealth and was going to mistry the defendant’s case purposely. The judge held a hearing and concluded that the son “suffers from serious psychiatric problems,” and that no reason had appeared to discharge the juror.

Over defense counsel’s objection, the judge then conducted a voir dire with the juror during which he explained to the juror the allegations made by his son and inquired whether the juror thought that those allegations would affect his fairness and impartiality as a juror. The juror responded that it would not, and the judge concluded that there was no reason to discharge the juror. Later that day, the juror asked to see the judge. The juror informed the judge that, due to his problems with his son, *547he could not concentrate, and that he was concerned about his heart condition. The judge concluded that good cause existed and, over defense counsel’s objection, dismissed the juror.

The judge had a duty to insure that the juror in question was capable of performing his duties. The initial voir dire with the juror was not improper; the jury were not sequestered, and the juror would probably learn of his son’s allegations if he did not know already. The juror’s subsequent indication that he was distracted by the problems with his son and worried about his own heart condition gave the judge good cause to dismiss the juror. “We do not . . . require jurors to serve at their peril.” See Commonwealth v. Leftwich, 430 Mass. 865, 874 (2000). The reason for the discharge was personal to the juror; it had “nothing whatever to do with the issues of the case or with the juror’s relationship with his fellow jurors.” Commonwealth v. Connor, 392 Mass. 838, 844-845 (1984).

10. Conclusion. A final thought is in order. The defendant’s trial was long and thorough, hard fought by capable counsel on both sides. The defendant’s counsel were particularly skillful in cross-examination, disclosing fully the weaknesses in the Commonwealth’s case, and ably developing an alternate interpretation of the facts: that the defendant was an exceptionally busy doctor who served large numbers of patients with clinical skill, but who was careless in record keeping; that, made aware of the overbillings, he cooperated fully in repaying the overcharges, continuing to serve his patients long after his Medicaid income was cut off. The differing interpretations of the defendant’s conduct were sharply drawn in a trial notable for its thoroughness. The choice was for the jurors, who demonstrated the closeness of the trial by the length of their deliberations. The trial was a fair one, and we see no adequate reason to disturb the verdicts.

Judgments affirmed.