A jury convicted the defendant of murder in the first degree and carrying a firearm without a license. On appeal, the defendant claims that numerous errors at trial warrant the reversal of his convictions and also requests relief pursuant to G. L. c. 278, § 33E. While this appeal was pending, the defendant filed a motion for postconviction relief, which we remanded to the Superior Court for disposition. The trial judge denied the motion, and the defendant’s appeal from that order has been consolidated with his direct appeal. We affirm the defendant’s convictions and decline to exercise our power under G. L. c. 278, § 33E.
1. Facts. We recite the facts in the light most favorable to the Commonwealth, reserving certain details for discussion in conjunction with the issues raised. On October 15, 1997, at approximately 1 a.m., the defendant and his friend, Edward Walker, were at a 7-Eleven store on Essex Street in Lynn. Four other young people, Eric Cruz, Latoya Graham, Tranece Barnes, and Eric Daniels, were also at the 7-Eleven store at the same time. The store’s surveillance videotape depicted the defendant staring at Cruz. When Cruz left the store and walked up Essex Street with his three companions, the defendant and Walker followed them. As they proceeded on Essex Street, Cruz was walking in front, with Daniels, Barnes, and Graham walking three abreast just a few feet behind him.
Once they had reached a dark, deserted stretch of the street, beyond the vicinity of the 7-Eleven store, Daniels heard a “clack” noise, which he recognized as the sound of a round being chambered in a semiautomatic weapon. He turned around, but saw nothing behind him except “a dark street.” There was a car parked on the side of the street, and the jury could have inferred that the defendant and Walker were hiding behind the car at the time Daniels turned around. A live cartridge was later found on the street near the parked car. A ballistics expert testified that that cartridge came from the defendant’s gun, and that, when tested, it failed to fire on three out of eight attempts. After a failed attempt to fire, one would have to pull the slide and reset it to engage the trigger again, a process that would eject the cartridge that had been in place at the time of the failed shot. From this evidence, the jury could have inferred that the defendant had attempted to shoot a round from his position behind the car, that the weapon had failed to fire, and that the defendant had pulled back the slide to chamber another round.
*342After seeing no one behind him, Daniels turned and resumed walking. The defendant and Walker then came out from their hiding spot behind the car and walked up right behind Daniels. The defendant stepped on the back of Daniels’s boot, whereupon Daniels turned around and saw the defendant and Walker about one and one-half feet away. Daniels asked the defendant what he was doing. Walker then told the defendant to give him the “strap,” a slang term for gun. The defendant reached into the front of his pants, pulled out a gun, and pointed it at Daniels, inches from his forehead. Daniels then grabbed the gun, and he and the defendant struggled over it for a few seconds. During this brief struggle, the defendant’s finger was on the trigger. The defendant “yanked” the gun back, and pulled the trigger. Graham, who was by then a little bit ahead of Daniels and a few feet behind Cruz, was struck in the head by a single bullet. She died at Lynn Hospital shortly thereafter.
The defendant was arrested later that morning. After being advised of his Miranda rights, the defendant made a statement to the police. The defendant stated, “I had a problem with the smaller dude. ... I had a beef with him over stuff he said.”1 According to the defendant, he followed Cruz out of the 7-Eleven store and down the street. He stated, “What was I going to do, pull the gun out in the store?” He pulled the gun out when he was about three feet from the group, at which point “[t]he taller one [Daniels] turned and grabbed the gun and it went off. I just shot. I did not move the slide first.”
2. Sufficiency of the evidence. The Commonwealth proceeded on the theory that the defendant had planned and intended to kill Cruz, and relied on the doctrine of transferred intent to prove murder in the first degree for the shooting of Graham. The defendant argues that the evidence was insufficient to prove deliberate premeditation or a specific intent to kill Cruz. We conclude that there was sufficient evidence to support the jury’s verdicts.
In reviewing a denial of a motion for a required finding of not guilty, we consider the evidence in the light most favorable to the Commonwealth to determine whether any rational trier of fact could have found the essential elements of the crime beyond a reasonable doubt. Commonwealth v. Cordle, 412 Mass. 172, 175 (1992). “The relevant question is whether the evidence *343would permit a jury to find guilt, not whether the evidence requires such a finding.” Commonwealth v. Lydon, 413 Mass. 309, 312 (1992). The Commonwealth may rely on inferences drawn from the evidence, so long as those inferences are “reasonable and possible.” Id. “To the extent that conflicting inferences are possible from the evidence, ‘it is for the jury to determine where the truth lies.’ ” Id., quoting Commonwealth v. Martino, 412 Mass. 267, 272 (1992).
The Commonwealth presented evidence that the defendant had a “problem” with Cruz and “had a beef with him over stuff he said.” When the defendant met Cruz by chance in the 7-Eleven store, he stared at him and then followed him out of the store. The defendant later acknowledged that he was armed at the time and, from his reference to the gun (“What was I going to do, pull the gun out in the store?”), the jury could infer that the defendant’s initial thought of using the gun on Cruz occurred while they were still in the store and that the defendant followed Cruz seeking a better opportunity to attack him. From Daniels’s testimony about hearing the sound of a round being chambered, combined with the discovery of a five cartridge on the street near the parked car, expert testimony that the cartridge was from the defendant’s gun, and tests showing that the defendant’s gun would regularly misfire, the jury could have concluded that the defendant had tried to shoot from his hiding place behind the car but that the gun had misfired. Following that failed attempt, the defendant then approached the group and pulled out his gun again, ready to fire (the safety off and a round already chambered), as he reached Daniels. The jury could have concluded that the defendant approached the group to get a closer shot at Cruz, but that Daniels stood in his way. The defendant pointed the weapon at Daniels, and, after Daniels grabbed the gun, the defendant “yanked” the gun back and “just shot” in the direction of Cruz.2 From this evidence, the jury could conclude that Cruz was the defendant’s intended victim, and that there had been a period of premeditation, from *344the encounter in the 7-Eleven store through the misfired shot behind the car, the confrontation with Daniels, and the ultimate firing of the weapon.
The defense also argues that, even if the jury could have found that the defendant had a premeditated intent to kill Cruz, the evidence was insufficient to show that the defendant had that intent at the precise moment the gun was fired. Specifically, he argues that, where the gun went off during the struggle with Daniels, it was unreasonable to infer that the defendant was aiming purposefully at Cruz at the time the gun was fired.
While the evidence concerning the struggle certainly raised the issue of accident and involuntary manslaughter,3 it did not prevent the jury from concluding that the shooting was intentional and that it was directed at Cruz. As discussed above, there was evidence that an intent to kill Cruz, and a plan to carry out that killing, had been formulated earlier. When the defendant confronted Daniels and Daniels grabbed the gun, the gun was already set to fire and the defendant’s finger was on the trigger. After just a few seconds’ struggle with Daniels, the defendant “yanked” the gun backward, and, as discussed above, the jury could conclude that the puffing of the trigger was not caused by any motion Daniels was making. The defendant’s own characterization of what happened (“I just shot”) is consistent with a purposeful firing of the weapon. The jury were also entitled to consider the direction the bullet was fired, which, in order to have hit Graham, was toward Cruz. The jury could conclude that the defendant was indeed aiming at Cruz but that, firing quickly and under pressure before Daniels could get the gun away from him, his aim was somewhat compromised, causing the bullet to hit Graham instead of Cruz.4 5-6 The defendant’s motions for a required finding of not guilty were properly denied.
*3453. Instruction on transferred intent. On appeal, the defendant argues that the judge’s instruction on transferred intent was deficient. Defense counsel did not object to the instruction when given and, in fact, specifically asked the judge to refrain from including the language that he now says should have been included. Therefore, we review whether any error in the instruction caused a substantial likelihood of a miscarriage of justice. Commonwealth v. Drumgold, 423 Mass. 230, 258 (1996), and cases cited.
The judge gave the following instruction on transferred intent: “When a person is killed who was not the person intended and if the intended victim had died and his death would be murder in the first or second degree, then the unintended killing of a bystander from any act directed at the person intended to be killed is criminal homicide of the same degree if proved by the Commonwealth beyond a reasonable doubt.”
The defendant argues that this instruction was erroneous because it did not make any reference to pointing, aiming, or pulling the trigger of a gun; therefore, the defendant contends, it reduced the Commonwealth’s burden of proof on the element *346of intent. We disagree. Although we have approved instructions on transferred intent in the past that used references to pointing or aiming a gun, we have not required that such language be included in the instruction. See Commonwealth v. Drumgold, supra at 259; Commonwealth v. Pitts, 403 Mass. 665, 669 & n.6 (1989); Commonwealth v. Puleio, 394 Mass. 101, 109-110 (1985). Rather, in each of the instructions we approved, there was other language explaining the law of transferred intent, and the references to aiming or pointing a gun at one person with the bullet then hitting someone else were given as hypothetical illustrations of the application of transferred intent. See Commonwealth v. Drumgold, supra; Commonwealth v. Puleio, supra.
In the present case, defense counsel specifically requested that the judge refrain from using any example that referred to pointing or aiming. Where the defendant’s theory was that the gun had gone off by accident during a struggle, and that he had not aimed or pointed the gun at anyone prior to its discharge, defense counsel understandably did not want the judge to give an example of aiming or pointing a gun as an illustration of the doctrine of transferred intent. Hypothetical examples that illustrate a legal doctrine can be very useful to the jury, but, as defense counsel appreciated, they can sway the jury if the specifics of the illustration are virtually identical to one party’s version of the facts of the case. To avoid that potential prejudice, the judge complied with defense counsel’s request and explained the law of transferred intent without providing an illustrative example.
The substance of the judge’s explanation of transferred intent was consistent with instructions we have approved. In both the Drumgold and Puleio cases, we approved instructions explaining that if a defendant intends to harm a person, “goes about harming” that person, but harms another person instead, the doctrine of transferred intent would apply. See Commonwealth v. Drumgold, supra; Commonwealth v. Puleio, supra. In this case, the instruction given was, if anything, more favorable to the defendant. The judge instructed that the jury must find that the victim was killed by an “act directed at the person intended to be killed” in order to convict the defendant. Without using examples involving pointing or aiming, the judge’s explanation that the unintended victim must be harmed by an “act directed at” the intended victim conveyed the same sense that the killing *347of the unintended victim must be the product of the defendant’s actual perpetration of the crime against the intended victim.6
4. Refusal of Eric Cruz to testify. Eric Cruz, the intended victim, testified at the probable cause hearing. He answered all of the questions asked by both the prosecutor and defense counsel, and he did not assert any privileges at that time. Most of that testimony paralleled the testimony of the other witnesses the Commonwealth presented at trial. Cruz, walking slightly ahead of the others, had not seen or heard any of the confrontation between the defendant and Daniels. He had heard what he described as a “chi chi” sound, which he recognized as coming from an automatic weapon, and the gun fired immediately after he heard that sound. Cruz had volunteered the opinion that, from the short interval between the mechanical sound and the gun’s going off, “it could have sounded like the gun went off by accident.” Cruz had started running the instant he heard the sound, and he did not see the actual firing of the gun, nor did *348he even know who had been hit. He did testify about prior confrontations with Walker, but claimed that, on seeing Walker in the 7-Eleven store, they had shaken hands.
However, between the time of Cruz’s probable cause testimony and the date of trial, Cruz had been incarcerated on a drug charge. On the first day of trial, prior to opening statements, the Commonwealth alerted the judge and defense counsel that Cruz was then saying that he was not going to testify at trial. The prosecutor explained that Cruz’s refusal to testify was not based on any invocation of his rights under the Fifth Amendment to the United States Constitution. Rather, the Commonwealth represented that Cruz’s refusal was based on the fact that he was incarcerated and that he now did not want to “rat on anybody.” The judge inquired of defense counsel, noting that it might be to the defendant’s benefit to have Cruz testify. Defense counsel agreed that “[i]t may very well be,” and made no objection to the prosecutor’s calling Cruz to the stand.
Cruz took the stand and answered a few preliminary questions identifying himself. He confirmed that he was presently serving a sentence on a drug charge. When asked if he remembered the night of October 14 into the early morning of October 15, 1997, he answered, “Nope.” On further questioning, he acknowledged that he had been with Daniels, Graham, and Barnes at the 7-Eleven store that night. When asked whether he remembered anything unusual occurring that night, he again answered, “Nope.” Cruz then asked to know the name of the prosecutor and, as the judge was answering him, Cruz interrupted with, “I’m not answering no more questions.”
The judge immediately excused the jury for a recess and, outside the jury’s presence, asked Cruz why he was refusing to testify. Cruz responded: “There is nobody here for me. None of my family is here and nobody I know. I don’t feel comfortable.” The judge warned him that, absent “a constitutional right to refuse to answer,” he would have to answer or be held in contempt. Cruz still refused to testify, whereupon the judge held him in contempt and sentenced him to ninety days from and after the sentence he was already serving.7 When the jury returned, the judge struck Cruz’s testimony from the record and *349gave the jury a curative instruction.8 The judge also invited defense counsel to submit a further jury instruction on the subject, and he gave defense counsel’s proposed instruction verbatim as part of his final charge to the jury.9
The defendant now contends that the jury’s observation of Cruz’s refusal to testify was the equivalent of Cruz’s invoking his Fifth Amendment privilege before the jury.10 See United States v. Harper, 579 F.2d 1235, 1240 (10th Cir.), cert, denied, 439 U.S. 968 (1978). We need not decide whether all refusals to testify should be treated as the equivalent of refusing to testify on Fifth Amendment grounds,11 because we find that, even if the witness in this case had asserted his Fifth Amendment *350privilege before the jury, there would be no substantial likelihood of a miscarriage of justice.
When it is clear that a witness intends to exercise the privilege against self-incrimination, the witness should not be permitted to do so before the jury. Commonwealth v. Hesketh, 386 Mass. 153, 158 (1982). Commonwealth v. Labbe, 6 Mass. App. Ct. 73, 79 (1978). Where there is some advance warning that a witness might refuse to testify, the trial judge should conduct a voir dire of the witness, outside the presence of the jury, to ascertain whether the witness will assert some privilege or otherwise refuse to answer questions.12 That precaution was not taken in this case, and the jury thus heard Cruz’s refusal to answer questions. However, reversal is not required in every case where the jury hear a witness assert some privilege or refuse to testify. Commonwealth v. Kane, 388 Mass. 128, 138 (1983). Commonwealth v. Martin, 372 Mass. 412, 414 (1977). Rather, when a witness refuses to answer questions in front of the jury, “[t]he inquiry is (1) whether the prosecutor has so unfairly exploited the matter as to constitute prosecutorial misconduct, and (2) whether inferences from the witness’s refusal to answer may have added critical weight to the prosecution’s case.” Commonwealth v. Kane, supra. See Commonwealth v. Martin, supra.
Neither factor is at issue in the present case. There was no prosecutorial misconduct in calling Cruz to testify. In this context, prosecutorial misconduct occurs when the prosecutor “question[s] a material witness in order to provoke a claim of privilege with a deliberate design to raise improper inferences in the minds of the jury.” Id. Here, Cruz had testified at the probable cause hearing without asserting any privileges or otherwise refusing to answer any questions. When Cruz signaled, immediately prior to trial, that he was then reluctant to testify, the prosecutor brought that fact to the attention of the judge and defense counsel. He did not exploit the situation or conceal the problem. It was, at that time, unclear whether Cruz would refuse to answer any questions outright or whether he *351would simply be an extremely uncooperative witness. As the prosecutor explained, he might have to “force[] [the prior testimony] down his throat in some ways.” That Cruz might refuse to testify outright, or might be a reluctant witness whose responses were entirely unpredictable, was fully disclosed prior to trial. Presumably because there were some aspects of Cruz’s probable cause testimony that were potentially helpful to the defendant, and because a reluctant (and unsympathetic) victim witness might generally weaken the Commonwealth’s case, defense counsel opted to run whatever risks there were in having such an uncooperative witness take the stand. That Cruz ultimately refused to testify cannot now be transformed into prosecutorial misconduct.
Nor did Cruz’s refusal to testify add “critical weight” to the Commonwealth’s case. In front of the jury, Cruz did not give any reason for his refusal, let alone a reason that would have assisted the Commonwealth. He was not a witness associated or affiliated with the defendant, but was instead identified in the evidence as a potential enemy of the defendant. Thus, whatever negative impressions the jury had of Cruz, they did not tarnish the defendant. Prior to expressing his refusal to testify, the jury heard that Cruz was presently serving a jail sentence on a drug charge, and they heard his acknowledgment, albeit a reluctant one, that he had been with the others at the 7-Eleven store in the early morning hours of October 15. At most, they might infer that, as an inmate, Cruz was reluctant to participate in any criminal prosecution.13 From the evidence presented through other witnesses, the jury learned that Cruz himself was walking up ahead and would not have been in a position to see the interaction between Daniels and the defendant at the time the shot was fired. Daniels, not Cruz, was the percipient witness to the critical events, and the jury would not have been swayed by whatever minimal impressions they gleaned about Cruz from his evasive answers and his ultimate refusal to testify. The prosecutor’s opening statement had not included any factual detail that was to have been provided by Cruz, and the prosecutor’s closing made no reference to Cruz’s refusal to *352testify. Cf. Commonwealth v. Martin, supra at 421-422 (witness’s invocation of Fifth Amendment before jury did not add critical weight to prosecution case, even though witness’s anticipated testimony had been described in detail in opening statement, where questions put to witness were not themselves “fact laden” and prosecutor’s closing did not refer to witness’s refusal to testify). Furthermore, the judge struck Cruz’s entire testimony from the record and gave two forceful instructions on the subject, one immediately following Cruz’s refusal to testify and another as part of the final charge. Cruz’s refusal to testify “could not have made the difference between acquittal and conviction.” Id. at 422.
5. Failure to instruct on self-defense and voluntary manslaughter. The defendant next contends that the judge erred in refusing to instruct the jury on self-defense and voluntary manslaughter. We reject these claims because the evidence, viewed in the light most favorable to the defendant, did not warrant the requested instructions. Commonwealth v. Pike, 428 Mass. 393, 395 (1998).
“If deadly force is used, a self-defense instruction must be given only if the evidence permits at least a reasonable doubt that the defendant reasonably and actually believed that he was in imminent danger of death or serious bodily harm, from which he could save himself only by using deadly force.” Commonwealth v. Hart, 428 Mass. 614, 615 (1999). Commonwealth v. Pike, supra. Commonwealth v. Reed, 427 Mass. 100, 102-103 (1998). Commonwealth v. Harrington, 379 Mass. 446, 450 (1980). A defendant must use all proper means to avoid physical combat prior to resorting to deadly force. Commonwealth v. Reed, supra. Commonwealth v. Hart, supra. “[T]he right of self-defense ordinarily cannot be claimed by a person who provokes or initiates an assault unless that person withdraws in good faith from the conflict and announces his intention to retire” (emphasis omitted). Commonwealth v. Naylor, 407 Mass. 333, 335 (1990), quoting Commonwealth v. Maguire, 375 Mass. 768, 772 (1978).
To support his request for a self-defense instruction, the defendant points only to testimony that, at the time the defendant drew the gun, Daniels’s hands were “[cjlosed” in front of him “as if he were going to use them to strike” the *353defendant.14 There was no evidence to show that, from this stance of Daniels alone, the defendant reasonably feared for his life. There was no evidence that Daniels was armed or that the defendant believed he was armed. To the extent that Daniels’s posture signaled a possible fistfight, the defendant had Walker at his side and had Daniels outnumbered. The defendant could not have reasonably believed that he was in imminent danger of death or serious bodily harm from Daniels.15
Moreover, the defendant had provoked the confrontation by deliberately stepping on the back of Daniels’s boot. “[S]elf-defense is unavailable to the person who initiates the fray.” Commonwealth v. Carrion, 407 Mass. 263, 268 (1990). The defendant had initiated this particular “fray,” and he made no effort to withdraw or announce his desire to withdraw before he pulled out the gun.16
Therefore, the right of self-defense never arose, and there was no error in denying the defendant’s request for a self-defense instruction. Where the defendant was not entitled to an instruction on self-defense, an instruction on voluntary manslaughter based on the use of excessive force in self-defense was also not required. Id.
6. Ineffective assistance of counsel. The defendant claims that trial counsel was ineffective in the following respects: failing to object to Eric Cruz’s being called as a witness; failing to offer Cruz’s probable cause testimony; failing to impeach Daniels with certain prior inconsistent statements; and failing to file a motion for disclosure of promises, inducements, and rewards.
In evaluating a defendant’s claim of ineffective assistance of *354counsel in a capital case, we consider whether there was error in the course of the trial and, if so, whether that error was likely to have influenced the jury’s decision. Commonwealth v. Wright, 411 Mass. 678, 681-682 (1992). When the claimed error is one involving the attorney’s strategic decisions, we give due deference to trial counsel’s tactical decisions and do not find ineffectiveness unless those decisions were “manifestly unreasonable when made.” Commonwealth v. Coonan, 428 Mass. 823, 827 (1999), quoting Commonwealth v. Martin, 427 Mass. 816, 822 (1998). See Commonwealth v. Iglesias, 426 Mass. 574, 580 (1998). We also recognize that, “[tjhroughout the course of a trial, defense counsel is called on to make numerous tactical decisions,” and therefore, “[a] list of subjective critiques of defense counsel’s decisions, absent a showing that errors likely affected the jury’s conclusions, is insufficient to support an ineffective assistance claim.” Commonwealth v. Scott, 428 Mass. 362, 369 (1998). We conclude that there was nothing manifestly unreasonable about trial counsel’s tactical decisions and no error that was likely to influence the jury’s conclusion.
(a) Failure to object to Eric Cruz’s being called as a witness. The defendant argues that his trial counsel erred in failing to object to Eric Cruz’s being called as a witness after the Commonwealth informed the court that Cruz was reluctant to testify. There was, as the judge noted at the time, potential benefit to the defense in having Cruz testify. Based on his probable cause testimony, it was reasonable to expect that, if he did testify at trial, Cruz would offer at least some testimony helpful to the defense. More importantly, to the extent that Cruz, the purported intended victim, was now reluctant to cooperate with the prosecution, there was the distinct possibility that Cruz’s trial testimony might be tilted even more in favor of the defense or that, at least, an uncooperative victim witness might give the jury an over-all unfavorable impression of the Commonwealth’s case. There was nothing manifestly unreasonable in counsel’s decision not to object to Cruz’s being called as a prosecution witness. Finally, as discussed supra at 349-350, there was no substantial likelihood of a miscarriage of justice resulting from Cruz’s taking the stand or from Cruz’s refusal to testify in front of the jury.
(b) Failure to introduce Cruz’s probable cause testimony. The defendant argues that defense counsel was ineffective in failing to offer Cruz’s probable cause testimony once Cruz *355refused to testify. In order to make out a claim of ineffective assistance based on this alleged error, the defendant would first have to establish that Cruz’s probable cause hearing testimony would have been admissible. The prior recorded testimony exception to the hearsay rule applies “where the prior testimony was given by a person, now unavailable, in a proceeding addressed to substantially the same issues as in the current proceeding, with reasonable opportunity and similar motivation on the prior occasion for cross-examination of the declarant by the party against whom the testimony is now being offered.” Commonwealth v. Trigones, 397 Mass. 633, 638 (1986), quoting Commonwealth v. Meech, 380 Mass. 490, 494 (1980).
It is unclear on this record whether Cruz was truly “unavailable.” We have held that a witness is unavailable if the witness makes a valid claim of privilege, Commonwealth v. Galloway, 404 Mass. 204, 208 (1989), but Cruz had not invoked any privilege as the basis for his refusal to testify for the Commonwealth. While the defendant claims that Cruz had a valid claim of privilege that he would have asserted had counsel been appointed to advise him, this argument is speculative. Cruz did not assert his Fifth Amendment privilege at trial, nor had he asserted the privilege at the probable cause hearing. Furthermore, there is no indication that the reason Cruz chose not to testify was in any way related to a fear of incriminating himself.
What Cruz did do at trial was refuse to testify, and the judge’s order that he testify and the imposition of sanctions for contempt did not change Cruz’s mind.17 While Proposed Mass. R. Evid. 804 (a) (2) would treat a witness as “unavailable” if the witness “persists in refusing to testify concerning the subject matter of his statement despite an order of the court to do so,” we have not yet adopted this proposed rule. To date, we have treated as “unavailable” those witnesses who are dead, ill, or missing (despite good faith efforts to locate them), or who have asserted a valid privilege. See Commonwealth v. Bohannon, 385 Mass. 733, 742-746 (1982); Commonwealth v. Canon, 373 Mass. 494, *356499-500 (1977), cert, denied, 435 U.S. 933 (1978); Commonwealth v. DiPietro, 373 Mass. 369, 380-386 (1977). “We do not, however, equate a refusal to testify, for example, with that measure of necessity which we have held permits the use of prior testimony.” Opinion of the Justices, 406 Mass. 1201, 1211 (1989).
Assuming, without deciding, that Cruz’s probable cause testimony could have been admitted based on his “unavailability,” the defendant has not shown that the admission of Cruz’s probable cause testimony would likely have affected the jury’s decision. The defendant contends that there were two items in Cruz’s probable cause testimony that would have been useful to the defense. First, Cruz testified that he had heard the mechanical “chi chi” sound of an automatic weapon immediately prior to the fatal shot, suggesting that the round was chambered as a result of the defendant and Daniels’s grappling with the gun. Although potentially helpful to the defendant,18 this aspect of Cruz’s probable cause testimony was cumulative of that of Daniels and Barnes.19 Barnes testified that she heard a “clicking noise” right before her ears began ringing from the sound of the gunshot, and Daniels testified that he “heard the gun click again and then it fired.” There was no dispute about this point (and indeed the prosecutor’s opening statement had told the jury that Barnes had heard “a click and a boom”), and there is no reason to believe that Cruz’s cumulative testimony on an undisputed detail would have had any effect on the jury’s decision.
The other aspect of Cruz’s testimony that the defendant contends would have been helpful was that Cruz himself had recognized only Walker in the 7-Eleven store and had not given any indication that he knew or recognized the defendant.20
The defendant argues that this information would weaken the *357Commonwealth’s theory as to motive and intent, as the defendant would have little reason to kill a person he did not even know. However, the defendant’s own statement acknowledged that he recognized Cruz, knew who he was, “had a problem” with him, and “had a beef with him over stuff he said.” Thus, whether Cruz himself recognized the defendant at the 7-Eleven store would not change the fact that the defendant certainly knew who Cruz was and admitted having some unspecified grudge against him. Cruz’s nonrecognition of the defendant would have had no effect on the jury’s assessment.
(c) Failure to impeach Daniels with prior inconsistent statements. The defendant also argues that defense counsel was ineffective in failing to impeach Daniels with certain prior inconsistent statements. Generally, failure to impeach a witness does not amount to ineffective assistance of counsel. See Commonwealth v. Bart B., 424 Mass. 911, 916 (1997), and cases cited. Even on the more favorable standard of review under § 33E, a claim of ineffective assistance based on failure to use particular impeachment methods is difficult to establish. Impeachment of a witness is, by its very nature, fraught with a host of strategic considerations, to which we will, even on § 33E review, still show deference.21 Furthermore, absent counsel’s failure to pursue some obviously powerful form of impeachment available at trial, it is speculative to conclude that a different approach to impeachment would likely have affected the jury’s conclusion.
Here, Daniels was subjected to extensive impeachment based on his criminal record and based on various changes in the different versions of events he had given. That defense counsel did not pursue additional avenues of impeachment does not constitute ineffective assistance. See Commonwealth v. Mitchell, 428 Mass. 852, 854-856 (1999), and cases cited.
(d) Failure to file a motion for disclosure of promises, induce-*358merits, and rewards. The defendant next complains that his counsel erred because he failed to file a discovery motion for disclosure of promises, inducements, and rewards. However, defense counsel had moved for discovery of exculpatory evidence, and “[t]he existence of ‘any understanding or agreement between the government and a key government witness’ is exculpatory evidence which must be revealed to the defendant, provided it is ‘material.’ ” Commonwealth v. Collins, 386 Mass. 1, 8-9 (1982), quoting Commonwealth v. Gilday, 382 Mass. 166, 175 (1980).
The defendant has not shown that there were promises, inducements, or rewards given to any Commonwealth witness. Contrast Commonwealth v. Hill, 432 Mass. 704, 711-717 (2000). The defendant hypothesizes that, because Daniels had a significant criminal record and exposure to criminal charges as a result of the events during the night of the shooting,22 it is likely that he was provided with some incentive for his testimony.23 In support of his suspicion that there must have been undisclosed promises, inducements, or rewards given to Daniels, the defendant points to Daniels’s acknowledgment that he did not tell the whole story about the incident until after he had spoken with an “Assistant Attorney General with the Suffolk County District Attorney’s Office.”24 However, the statement Daniels gave to the police after he spoke with someone at the district attorney’s office was more favorable to the defendant than the first statement he had given the police on the night of the shooting, and it was not until that second statement that Daniels acknowledged any form of struggle over the gun.25 There is no reason to believe that promises, inducements, or rewards were provided to Daniels to obtain his cooperation where, after his discussion with a prosecutor, Daniels actually *359changed his version of events to one that was far less helpful to the Commonwealth and, in many respects, very favorable to the defendant. Where the defendant has shown nothing to suggest that any Commonwealth witness was in fact promised something in return for testimony, we cannot find ineffective assistance of counsel arising out of defense counsel’s reliance on his motion for discovery of exculpatory evidence (instead of a specific motion for promises, inducements, or rewards).
7. G.L. c. 278, § 33E. We have reviewed the entire record of the defendant’s trial pursuant to G. L. c. 278, § 33E, and we see no reason to exercise our authority to reduce the jury’s verdict or order a new trial.
Judgments affirmed.
Order denying motion for post-conviction relief affirmed.