The defendant was charged with the murder of a Worcester nightclub manager, the armed robbery of the nightclub’s assistant manager, assault and battery of the assistant manager by means of a dangerous weapon, armed assault with intent to rob (two indictments), intimidation to steal from a depository (two indictments), breaking and entering at nighttime with intent to commit a felony, possession of a sawed-off shotgun, and possession of ammunition without a firearms identification card. In 2002, a Superior Court jury convicted the defendant of all charges except assault and battery of the assistant manager by means of a dangerous weapon. He received concurrent life sentences for the convictions of felony-murder,1 possession of a sawed-off shotgun, armed robbery, and the intimidation of the assistant manager in order to steal from a depository. In addition, he received concurrent sentences of from eighteen to twenty years for armed assault of the victim and the assistant manager with intent to rob, and for breaking and entering. The judge filed the conviction of possession of ammunition without a firearms identification card, the defendant not objecting.
On appeal, the defendant claims that the trial judge erred in admitting in evidence the defendant’s statement to the police, and in various instructions to the jury. In addition, he asks that we grant him a new trial or reduce the murder verdict to murder in the second degree. See G. L. c. 278, § 33E. Because we find no error that warrants a reversal of the defendant’s convictions and see no reason to exercise our power pursuant to G. L. c. 278, § 33E, we affirm the defendant’s convictions.
Facts and procedural background. We recite the facts the jury were warranted in finding, reserving certain details for our discussion of the issues raised.
On May 28, 2000, at approximately 1 a.m., the defendant was being driven home by his father from police custody and “was *722already planning to do the robbery” at the Worcester nightclub which he had “cas[ed]” and thought about doing for “a couple of months.” On that day, the defendant had long “bright yellow” hair. Although the defendant had taken approximately thirty Klonopin pills at approximately 1 a.m. on May 27, 2000, he subsequently had been in police custody for nine to ten hours before his father arrived to drive him home. At home, he went to bed, pretended to sleep, and waited for his father to go to sleep. Sometime before 3:30 a.m. on May 28, 2000, he donned a hat, a bandana (to hide his face), a painter’s suit, a turtleneck shirt (to cover his tattoo), and black boots. He took a pistol-grip sawed-off shotgun and a black canvas bag that contained gloves, a radio, wire ties, a knife, and duct tape. He walked from his house to the nightclub, a distance of approximately 1.2 miles. When he got near the building’s back door, while in some nearby brush, he loaded the shotgun and, in the process, dropped a shell. He walked into the building through an unlocked door, made a loop inside to see if anyone was around, and then went down some stairs to where the office was located. The victim and the assistant manager were in the office.
Moments after entering the office, the defendant shot the victim and then leaned over him, screaming his name and demanding that he open the safe. When the defendant did not receive a comprehensible response,2 he turned to the assistant manager and demanded the combination, which she did not know. He took the assistant manager’s handbag and her car keys. He asked her what kind of car she drove, its color, and where it was parked. He then stole the vehicle, a Jeep Cherokee, and drove it to a street near his house. He abandoned the vehicle and walked to another nearby street; he took all his clothes off except his underwear and threw them into a catch basin. He also threw everything else he had, including the shotgun, the purse, and the keys, into the basin.
The defendant then walked home. He searched through his house looking for his mother’s medications. He found them and took them all. His father found him unconscious, with his eyes *723open, at approximately 7 a.m. on May 28, 2000. The defendant was rushed to a hospital.
In the meantime, the nightclub assistant manager had telephoned 911. She was not able to identify the perpetrator because he had a bandana over his face. The victim died of a shotgun wound to the chest. At trial, counsel stipulated that the shot was fired at close range.
The police recovered all items the defendant disposed of, as well as the Jeep, in the course of their investigation.3 The police also recovered a shell casing in the office, and shells on the stairs leading to the office and outside in the brush. After the police found the vehicle and items in the catch basin, they suspected that the defendant was involved. He was arrested on a default warrant (unrelated to the murder) at his house on June 6, 2000. On the day of his arrest, he had short brown hair (instead of long yellow hair) and denied any involvement in the homicide to Worcester detectives. The defendant remained in jail, and the police continued their investigation.4
On June 9, 2000, a Worcester detective contacted the defendant’s father and asked him to come to the station to give a statement concerning the defendant’s whereabouts on the morning of the murder. After taking the statement, the detective told the father that the defendant was the prime suspect in the homicide because the police had found the stolen Jeep and items in a catch basin near the defendant’s house. The father also was told that a witness had seen someone matching the defendant’s description running up the front stairs to his house at approximately 4 a.m. on the morning of the murder. The detective also told the father that the shooting could have been an accident. He testified that he told the father that because the assistant manager had said that the shooter asked the victim for the combination to the safe only after the victim was mortally
*724The next day, the father related this conversation to the defendant, who asked his father to have the police speak to him. Later that evening, the defendant met with two detectives who took his statement, which contained most of the information discussed supra.
The defendant filed a motion to suppress his statement to the police, which was denied. At trial, over objection, a redacted version of the statement was read to the jury and counsel stipulated that the defendant was not under the influence of alcohol or drugs at the time he gave his confession. The defendant did not testify at trial. His defenses were that the shooting was an accident, and his expert testified that due to various mental disorders stemming from emotional and sexual abuse in his childhood, he was incapable of forming the requisite intent to commit the crimes. He also claimed that his statement to the police was not voluntary.
Discussion. 1. Miranda waiver and voluntariness issues. The defendant argues that the Commonwealth did not meet its burden to prove, beyond a reasonable doubt, that the defendant’s waiver of his Miranda rights and his subsequent confession were voluntary. He argues, among other things, that he confessed only after a detective told his father that he (the detective) thought the shooting was an accident and that the defendant would receive some leniency if he confessed.
“The Commonwealth bears the burden of proving beyond a reasonable doubt, in the totality of the circumstances, that a defendant’s [Miranda] waiver was voluntary, knowing and intelligent, and that his statements were voluntary.” Commonwealth v. Auclair, 444 Mass. 348, 353 (2005), citing Commonwealth v. Jackson, 432 Mass. 82, 85-86 (2000). “Absent clear error, we accept a motion judge’s findings of fact, . . . and a finding of *725voluntary waiver is given substantial deference” (citations omitted). Commonwealth v. Auclair, supra. In looking at the totality of the circumstances to determine the voluntariness of a statement, the judge may consider, among other things, “promises or other inducements, ... the initiator of the discussion of a deal or leniency (whether the defendant or the police), and the details of the interrogation.” Commonwealth v. Magee, 423 Mass. 381, 388 (1996), quoting Commonwealth v. Selby, 420 Mass. 656, 663 (1995).
“An officer may suggest broadly that it would be better for a suspect to tell the truth, may indicate that the person’s cooperation would be brought to the attention of the public officials or others involved, or may state in general terms that cooperation has been considered favorably by the courts in the past. What is prohibited, if a confession is to stand, is an assurance, express or implied, that it will aid the defense or result in a lesser sentence.” (Footnotes omitted.) Commonwealth v. Meehan, 377 Mass. 552, 564 (1979), cert. dismissed, 445 U.S. 39 (1980). See Commonwealth v. Jordan, 439 Mass. 47, 53 (2003), citing Commonwealth v. Meehan, supra at 564 (“The touchstone is whether the police ‘assured’ the defendant that his confession would aid his defense or result in a lesser sentence”).
It is undisputed that, when he spoke to the father, the detective stated that the shooting could have been an accident and that if the defendant cooperated, the detective would bring it to the attention of the district attorney and that the defendant “may see the light of day down the road.” What is contested is whether there was an assurance of leniency.
In his affidavit in support of his motion to suppress his statement to the police, the defendant stated that during his first interview on June 6, 2000, the police told him, “If you confess, it will be a manslaughter charge.” The defendant also averred that, when he asked to telephone an attorney, the police provided him with a telephone and telephone book, but told the defendant that if he made the call “all deals are off the table.”6 In addition, the defendant’s father testified that when he spoke to the *726detective on June 9, 2000, the detective told him that the police had offered the defendant a manslaughter charge but that the defendant would not take it.
At a hearing on the motion to suppress, Worcester detectives denied offering a deal or reduction in the crime charged to the defendant either at the June 6 interview or in the conversation with the father. In addition, the Commonwealth called a correction officer who had known the defendant in high school and who saw the defendant at the jail. He testified that he saw the defendant the night he confessed. The next morning he asked the defendant where he had been coming from the night before. The defendant stated that he had confessed to a murder, that he “was going to get life,” that the police had evidence, and that “other people were going to be blamed.” The Commonwealth also offered some of the statements that the defendant made in telephone conversations recorded at the jail after his confession. In those conversations, the defendant explained that he was “never getting out,” because he had committed a murder during a robbery.
In crediting the Commonwealth’s version of the statements made to the defendant and the father, the motion judge especially credited the testimony of the correction officer and the content of the defendant’s telephone conversations, finding that they “evidenced the defendant’s state of mind that he was facing life imprisonment, and not the lesser charge of manslaughter.” We accept a judge’s resolution of conflicting testimony. Commonwealth v. Ortiz, 435 Mass. 569, 577-578 (2002), citing Commonwealth v. Yesilciman, 406 Mass. 736, 743 (1990). See Commonwealth v. Jordan, supra at 53 (defendant’s state of mind at time of confession confirmed by his later statements).
The defendant argues that, in any event, the detective’s undisputed statement to the father that the defendant “may see the light of day down the road” implied that he would receive a lenient sentence, and the detective’s statement that the shooting was an accident was an attempt to minimize the crime.7 Citing Commonwealth v. DiGiambattista, 442 Mass. 423 (2004), the *727defendant argues that these statements induced the defendant to confess rather than seek legal advice. Id. at 433-434, 439 (combination of false statement of evidence and implied promise of leniency rendered defendant’s confession involuntary).
The “light of day” comment was prefaced by the word “may” and was stated to the father in the context of the police bringing the defendant’s cooperation to the attention of the district attorney’s office. The motion judge did not err in finding that the statement did not coerce the defendant into confessing because the detective did not promise a lesser sentence and did not hold himself out as possessing the authority to enter into a plea with, or reduce the charges for, the defendant. Commonwealth v. Jordan, supra at 52-53, and cases cited. Commonwealth v. Meehan, supra at 564.
The defendant did not raise, and the motion judge did not discuss, the statement about the shooting being an accident, although the undisputed testimony was presented at the motion hearing. Minimizing a crime implies leniency. Commonwealth v. DiGiambattista, supra at 436. However, minimizing a crime alone does not render a statement involuntary; it must be considered as a factor in the totality of the circumstances. Id. at 438-439. We assume, without deciding, that this statement was a minimization of the crime.8 Here, the minimization was not combined with any false statement concerning the evidence or the strength of the Commonwealth’s case, and the detective “stopped short of making an assurance” regarding the benefits of confessing. Commonwealth v. Scoggins, 439 Mass. 571, 577 (2003). Cf. Commonwealth v. DiGiambattista, supra at 433-434, 436, 439-440 (officers lied about evidence and minimized crime by calling it “understandable, justifiable, excusable . . . not that serious” and resolvable through counselling). In addition to finding that the defendant’s subsequent statements showed that he did not believe he was going to receive a lesser sentence, the judge found that the defendant was twenty-five *728years old at the time of his statement, had experience with the legal system, was of sound mind, was calm, and was interrogated for only two and one-half hours. The motion judge further found that the defendant indicated three times that he understood and waived, both orally and in writing, his Miranda rights. We see no reason to disturb the motion judge’s conclusion, based on a consideration of the totality of the circumstances and fully supported in the record, that the defendant’s waiver of his Miranda rights was knowing, voluntary, and intelligent and that his statement to the police was voluntary.9
2. Absence of electronic recording of defendant’s statement. The defendant argues that the judge’s denial, over his objection, of his request for an instruction to the jury concerning the absence of an electronic recording of the defendant’s statement was highly prejudicial and limited the defendant’s ability to challenge the voluntariness of his confession.10 The judge stated that defense counsel could argue the issue to the jury. There was no abuse of discretion or error of law.
This case was tried before this court’s decision in Commonwealth v. DiGiambattista, supra at 425, 447-448, prospectively to require such an instruction if a defendant’s unrecorded confession or statement that is the product of “custodial interrogation” or “an interrogation conducted at a place of detention” is admitted in evidence, and the defendant requests the instruction.11 See Commonwealth v. Dagley, 442 Mass. 713, 721 (2004), cert. denied, 544 U.S. 930 (2005). The defendant argues that the rule in the DiGiambattista case should, in the circumstances of this case, be applied retroactively. We have *729rejected such a request and see no reason to revisit the issue. Commonwealth v. Dagley, supra.
Here, contrary to the defendant’s assertion, the judge did not prevent the defendant from placing the issue of the absence of a recording before the jury.12 The judge explicitly told defense counsel that he was free to argue the issue in closing, which counsel chose not to do. Defense counsel did cross-examine the detective who interviewed the defendant on June 6, the conversation in which the defendant claims the offer of manslaughter occurred,13 about whether the conversation was recorded, but not the detective to whom the defendant confessed on June 10. See Commonwealth v. Diaz, 422 Mass. 269, 273 (1996) (defense counsel entitled to pursue issue of absence of *730recording). In addition, defense counsel argued voluntariness to the jury, emphasizing that the detective’s discussion with the defendant’s father was what caused the defendant’s confession. Even if defense counsel should have emphasized the lack of a recording of the defendant’s confession on June 10, the defendant’s argument concerning voluntariness was that he confessed because he expected leniency based on previous discussions with the police that both he and his father had had. However, his statement to the correction officer the morning after the defendant had confessed, in which he said, among other things, that he was going to go to prison for life, clearly shows that the defendant had expected no leniency.
3. Jury instructions. The defendant argues that the judge erred in instructing the jury on reasonable doubt, circumstantial evidence, and inferences, the combination of which, he contends, unconstitutionally diminished the level of certainty required for the Commonwealth to establish guilt.
a. Reasonable doubt. The defendant claims that when the judge instructed the jury on reasonable doubt, he omitted language from the approved charge set forth in Commonwealth v. Webster, 5 Cush. 295, 320 (1850). Some of the language that the defendant states was omitted is not part of the approved instruction.14 The judge’s instruction to the jury on reasonable doubt is as follows:15
“As I said, the burden of proof in a criminal case is upon the Commonwealth. The law never imposes upon a defendant the burden of producing any evidence or calling any witnesses. And the Commonwealth must prove each and every essential element of the charge beyond a reasonable doubt. Because that’s a critical proposition in any criminal case, proof beyond a reasonable doubt, there is a *731definition that was written about a hundred and forty years ago. The language is somewhat stilted. I’d ask you to be attentive as I read it to you. What is reasonable doubt? The term is often used and probably pretty well understood, but it is not too easily defined. It is not mere possible doubt, because everything relating to human affairs and depending upon evidence is open to some possible or some imaginary doubt. Reasonable doubt is that state of the case when after the entire comparison and consideration of all of the evidence your minds are left in that condition that you cannot say that you feel an abiding conviction to a moral certainty of the truth of the charge. The burden of proof is upon the prosecution. All the presumptions of law independent of evidence are in favor of innocence. And every person is presumed to be innocent until he is proven guilty. If upon such proof there is reasonable doubt remaining, the accused is entitled to the benefit of it by a finding of not guilty. It’s not sufficient to establish a probability, even a strong probability that the fact charged is more likely to be true than not true. But the evidence must establish the truth of the charge to a reasonable and moral certainty, a certainty that directs and convinces your understanding and satisfies your reason and your judgment.t16] All right, what I have just read to you is the definition of proof beyond a reasonable doubt. The Commonwealth must prove each and every essential element of the charge beyond a reasonable doubt before you may find the defendant guilty of the charge. The Commonwealth is not required to prove the case to an absolute certainty. The Commonwealth is not required to prove the case to a mathematical certainty. Mathematical certainty is that level of certainty you’d have if you add ten and ten and arrive at twenty. The Commonwealth is not required to prove the case to an absolute or mathematical certainty, but it must prove each and every element of the charge beyond a reasonable doubt before you may find the defendant guilty of the charge.”
There was no error. The issue in a Webster-type charge is the *732moral certainty language, which would constitute reversible error if it were not linked to language that impresses on the jury the high degree of certainty that is required to find the defendant guilty. Commonwealth v. Pinckney, 419 Mass. 341, 344 (1995). We have stated that the Webster charge itself, even though it uses moral certainty language, is acceptable. Id. However, a verbatim Webster charge is not required. See Commonwealth v. Watkins, 433 Mass. 539, 547 (2001) (approving “a charge defining reasonable doubt in accordance with the Webster model”); Commonwealth v. Gagliardi, 418 Mass. 562, 568 n.3 (1994), cert. denied, 513 U.S. 1091 (1995), and cases cited (“faithfully tracks [Webster] language”). See also Commonwealth v. Riley, 433 Mass. 266, 271-272 (2001). What is critical is that the moral certainty language be “linked with language that lends content to the phrase.” Commonwealth v. Pinckney, supra at 345, citing Commonwealth v. Gagliardi, supra at 571. That was done here.
Like the judge in Commonwealth v. Gagliardi, supra, the judge omitted language from the Webster charge that told the jury that absolute certainty was not required. Commonwealth v. Gagliardi, supra at 568 n.3. Here, the judge substituted language concerning mathematical certainty, language we have approved. See, e.g., Commonwealth v. Mack, 423 Mass. 288, 290-291 (1996) . See also Commonwealth v. James, 424 Mass. 770, 788 (1997) , quoting Commonwealth v. Mack, supra at 291 (“we do not require that judges use any particular words to instruct the jury”). There is no evidence that the jury did not “listen attentively to the judge’s instructions.” Commonwealth v. James, supra. The judge made them stand for a moment17 just before he read the charge, asked them to listen attentively, and told them that reasonable doubt is a “critical proposition.” Moreover, there is no evidence that the jury did not understand the high degree of certainty required to find the defendant guilty. See id. Indeed, the jury did not convict the defendant of murder in the first degree on a theory of deliberate premeditation or of assault and battery of the assistant manager by means of a danger-*733pus weapon. Accordingly, there is no “ ‘reasonable likelihood’ that the instruction led the jury to believe that they could convict the defendant on proof insufficient to dispel reasonable doubt.” Commonwealth v. Denis, 442 Mass. 617, 621 (2004), citing Commonwealth v. Pinckney, supra at 342.
b. Circumstantial evidence and inferences. The judge denied the defendant’s requested jury instruction on circumstantial evidence. The defendant argues that various portions of the instruction the judge gave on circumstantial evidence and inferences are erroneous.
We need not belabor this point because it is unsupported by citation to authority and, therefore, does not rise to the level of appellate argument. We have reviewed the instruction, considering it as a whole, and conclude that there was no error. See Commonwealth v. Sann Than, 442 Mass. 748, 752 (2004), quoting Commonwealth v. Richardson, 429 Mass. 182, 185 (1999) (court looks at “the charge as a whole to determine whether it fairly instructs the jury”).
4. General Laws c. 278, § 33E. We have reviewed the entire record and considered all the defendant’s claims of error pursuant to G. L. c. 278, § 33E. We find nothing indicating a substantial likelihood of a miscarriage of justice and see no reason to reduce the murder verdict or order a new trial.
Judgments affirmed.