On March 7, 1979, the defendant was convicted by a jury of murder in the second degree on an indictment comprehending murder in the first degree. The defendant moved for a new trial on the ground that the verdict was against the weight of the evidence. After the motion was denied, the defendant filed her claim of appeal from both the verdict and the denial of the motion. New counsel was appointed, and on April 22, 1980, the defendant filed a second motion for a new trial on the ground of newly discovered evidence. Mass. R. Grim. P. 30,
We summarize the facts. At approximately 10:15 p. m . on August 13,1978, Robin Mines, Dianne Tinsley, and the victim, Denise Curry, were on Whitfield Street in Dorchester when a car passed them driven by a female accompanied by two male passengers. Some epithets were exchanged between the victim and one of the passengers, whereupon the *577 car stopped and the occupants emerged. The female approached the victim, and after some words were exchanged, began hitting her repeatedly, while the two males prevented Robin Mines and Dianne Tinsley from interfering. At some point, one of the men pulled the assailant off the victim and said, “Taney, let her go, let her go.” As the assailant relinquished her hold, Mines observed something “long” and “bloody” in the hand of the assailant. The two men and the assailant went back to the car and drove off. The victim staggered a few steps and collapsed; she died shortly thereafter of a stab wound to the heart. A medical examiner testified that the wound could have been caused by a knife or a pair of scissors.
Shortly after the incident, Mines described the attacker to the police as a black woman, five feet, ten inches tall, weighing 165 pounds, and wearing an “Afro” type hair style. Tinsley also described the attacker as tall and wearing an Afro. Mines told the police that she recognized the assailant as one of the Toney sisters, and directed them to the home of Dorcas Toney, a sister of the defendant. The next day, Mines and Tinsley went with the police to see Dorcas Toney. After Dorcas was observed by Mines and Tinsley, they told the police she was not the assailant. Shortly thereafter one of the police officers mentioned the defendant’s name, whereupon Mines told them that that was the one who had committed the crime. No in-person or photographic identification procedure involving the defendant was conducted prior to trial.
The defense at trial was that of mistaken identity. There are approximately ten Toney sisters, 1 and the defendant introduced evidence suggesting that one of her sisters was the proper suspect, and not the defendant. There was unrebutted evidence that the car involved belonged to the defendant. It was shown at trial that the defendant was five feet, six inches tall, weighed 135 pounds, and usually, if not al *578 ways, wore her hair tied back. Doris, on the other hand, was described as five feet, nine inches tall, between 165 and 170 pounds, and wearing an Afro, a description corresponding closely to the one that Mines and Tinsley had given to the police on the night of the murder. Despite these discrepancies, Mines testified positively that the defendant was the assailant, stating that she knew the defendant from having attended a Toney family party, and having frequented the same skating rink as the defendant. Dianne Tinsley could not provide a positive identification, other than by saying that, as compared with the assailant, the defendant was “the right size.”
As an alibi, the defense introduced evidence to show that on the evening of the incident, members of the Toney family had visited two sisters incarcerated at the Massachusetts Correctional Institution at Framingham. Several members of the family testified that, although the defendant drove her car to the prison, she returned with her father in his car directly to her sister Maryse Beane’s house where she stayed until 2 a.m. The evidence indicated that Doris had left the prison beforehand in the defendant’s car, accompanied by the defendant’s fiance", brother-in-law, and several other family members. This was corroborated by the testimony of the correctional officer who was checking in visitors that evening. The officer testified that the defendant had put a pair of scissors and other belongings into a locker, but that another family member, who the defendant argues was Doris, emptied the locker and left the prison before the defendant did. The officer remembered the defendant’s being angry over the fact that someone else had emptied her locker. There was evidence that the defendant had put her car keys into her locker when she arrived at the prison. Finally, the correctional officer stated that the defendant wore her hair rolled up in a bun that evening. On rebuttal the prosecution introduced in evidence visitation records of the prison which did not list a Doris Toney as having been there that evening. There was also evidence, however, that these records were not always accurate.
*579 The defendant raises five claims of error. These relate to (1) the motion for a new trial on the basis of newly discovered evidence; (2) the defendant’s motion for a directed verdict at the close of the Commonwealth’s case; (3) the admission at trial of evidence of flight by the defendant, and the instructions to the jury relating to this evidence; (4) the admission at trial of Mines’s in-court identification of the defendant; and (5) the defendant’s request for an order granting Doris Toney use immunity. For the reasons set forth below we conclude that there has been no error, and that relief under § 33E is not appropriate.
1. Motion for a New Trial on the Ground of Newly Discovered Evidence.
The defendant offered the affidavits of seven witnesses in support of her motion for a new trial. She claims that the judge erred in denying the motion without an evidentiary hearing.
Rule 30 (b) of the Massachusetts Rules of Criminal Procedure,
Affidavits of Ralph Jackson and Jeffrey Beane.
Both Ralph Jackson and Jeffrey Beane stated in their affidavits that they were passengers in the car driven by the assailant
*580
and that they witnessed the fight that resulted in Denise Curry’s death. Ralph Jackson is the defendant’s fiance, and Jeffrey Beane is the defendant’s brother-in-law. They both stated that the defendant was not present when the incident occurred. However, they did not volunteer any information concerning the identity of the assailant. The judge was not required to believe their statements.
Commonwealth
v.
Cassesso,
Affidavits of Cynthia Bruton and Irving E. Laval. Cynthia Bruton shared an apartment with Robin Mines. Her affidavit stated that before the defendant’s trial Robin Mines told her that she (Mines) “knew it wasn’t Greer [the defendant], but if Greer was going to be funny and take the weight for someone else, Robin would say it was Greer, [because] somebody was going to pay for Denise’s death.” Laval, a boy friend of Mines, stated in his affidavit that “Robin told me that Denise Curry had been stabbed by Tracy Toney, with a butcher knife and that Robin had seen it.” When Laval challenged her identification of Tracy as the assailant, Mines replied, “Well, if it wasn’t Tracy, it was *581 her other sister. . . . It’s one of them, I know that much and they’re going to pay for this.”
The judge ruled that this evidence was merely cumulative, and that the defendant had failed to show that these witnesses were unavailable at trial. We agree. The testimony is hearsay, and is admissible only for its impeachment value. See generally P.J. Liacos, Massachusetts Evidence 141-142 (5th ed. 1981). It is cumulative of other evidence that was adduced at trial to impeach Mines’s testimony. Newly discovered evidence that tends merely to impeach the credibility of a witness will not ordinarily be the basis of a new trial.
Commonwealth
v.
Cassesso, supra
at 576, and cases cited. See
Commonwealth
v.
Stewart,
Affidavits of Mary Cournoyer, Gertrude Apkarian, and Willie Curry. Mary Cournoyer and Gertrude Apkarian were employed at the Massachusetts Correctional Institution, Framingham, at the time of the incident. According to their affidavits, their testimony would tend to establish the time when the defendant left the prison on August 13, that she did not have an Afro hair style that evening, and *582 that the visitation records of the prison were not always accurate. The judge was correct in concluding that this evidence was merely cumulative of evidence that had already been adduced at trial. The affidavit of Willie Curry, the defendant’s hairdresser, was also cumulative, inasmuch as it only tended to prove that the defendant did not wear an Afro.
2. Motion for Directed Verdict.
After the close of the Commonwealth’s case, the defendant made a motion for a directed verdict, which the judge denied. The defendant contends that the denial of the motion was error.
Applying the standard set forth in
Commonwealth
v.
Latimore,
We conclude that the evidence was sufficient to warrant the submission of the case to the jury. The witness Robin Mines made a positive in-court identification of the defendant as the assailant. She testified that she had seen the defendant on a number of occasions before the murder — several times at a skating rink, and once at a party. She also testified that she knew the defendant and several other Toney sisters by sight. The fact that Mines’s in-court identification was inconsistent with the description given to the police shortly after the murder does not render the evidence insufficient. The credibility of a witness is for the jury to decide. There was no error in denying the motion for a directed verdict.
Commonwealth
v.
Vitello,
3. Evidence of Flight.
Over the objection of the defendant, the Commonwealth introduced evidence that several law enforcement officers tried to locate the defendant by going to her house on several occasions, and by talking, either by telephone or in *583 person, to four of the defendant’s sisters and one of her cousins. The defendant countered with evidence tending to show that she would have been at work during the times when the police came to her house, and that she did not know until just before she surrendered herself to the police that she was being sought in connection with the murder. In rebuttal, the Commonwealth introduced evidence suggesting that the defendant failed to report to work after the murder.
The defendant concedes that evidence of flight is admissible to prove consciousness of guilt.
Commonwealth
v.
Gilday,
The defendant also argues that the judge erred in his instructions to the jury on evidence of flight by failing to bring to their attention the defendant’s innocent explanation for the alleged flight. 3 The defendant did not object to this portion of the charge. Our review under G. L. c. 278, § 33E, is therefore limited to determining whether there is substantial likelihood that a miscarriage of justice has occurred. Commonwealth v. Tavares, ante 140, 147-148 (1982), and cases cited. However, because the issue has not previously been addressed fully by this court, we make some observations relative to jury instructions on evidence of flight. 4
There are two assumptions that underlie the inference of guilt that may be drawn from evidence of flight, concealment, or similar acts. The first assumption is that a person who flees or hides after a criminal act has been committed does so because he feels guilt concerning that act. The second is that one who feels guilt concerning an act has committed that act. 1 J. Wigmore, Evidence § 173 (3d ed.
*585
1940). See
Miller
v.
United States,
We think that a judge should instruct the jury (1) that they are not to convict a defendant on the basis of evidence of flight or concealment alone (see, e.g.,
Commonwealth
v.
Smith,
It is clear that the judge did not err in instructing the jury. The charge adequately cautioned the jury concerning the equivocal nature of evidence of flight. 6
*586 4. Identification Testimony.
The evidence at trial indicated that Robin Mines told the police that the defendant was the attacker only after one of the police officers had mentioned the name Greer Toney to her. The defendant argues that Mines’s in-court identification was for this reason a product of impermissible police suggestion. Analogy is drawn to cases involving one-on-one photographic or in-person confrontations. See, e.g.,
Commonwealth v. Venios, 378
Mass. 24 (1979);
Commonwealth
v.
Botelho,
The defendant does not cite, nor have we found, any cases holding that the mentioning of a name by police may by itself be so suggestive as to render any subsequent identification excludable.
7
Assuming that it may, however, the record in this case does not show that the mention of the defendant’s name was unnecessarily suggestive. The defendant bears the burden of establishing that a confrontation is unnecessarily suggestive.
Commonwealth v. Venios, supra
at 26-27.
Commonwealth v. Botelho, supra.
The tran
*587
script shows only that the police officer “mentioned” the defendant’s name, whereupon Mines responded that that was the person who attacked the victim. There is nothing to indicate that the police officer suspected the defendant as the assailant when she mentioned her name, or that any such suspicion was conveyed to Mines.
8
These facts do not establish an unnecessarily suggestive “confrontation.” Since the mentioning of the defendant’s name has not been shown to be unnecessarily suggestive, no taint attached to the in-court identification. We need not consider, therefore, whether the identification was “reliable,” and, if so, whether it would be constitutionally admissible despite an impermissibly suggestive confrontation. See
Commonwealth
v.
Storey,
5. Use Immunity.
The defendant filed a motion asking the judge for an order granting use immunity to Doris Toney in exchange for her testimony. As grounds for the motion, she asserted that Doris Toney would confirm the fact that the defendant was not at the scene of the murder and did not stab the victim. The judge took no action on this motion. The defendant has renewed her motion in this court.
This court has not decided whether the courts of this Commonwealth have the authority to grant immunity to a defense witness over the objection of the prosecutor,
9
and
*588
we express no opinion on whether such authority exists. It is the defendant’s contention that she has a constitutional right to procure the testimony of Doris Toney by means of a court-ordered .grant of use immunity. Regardless of whether such a constitutional right exists, she has not presented to this court or to the trial judge the factual basis necessary to support her motion. Doris Toney has not come forward with any statement, sworn or unsworn, that she intends to invoke her privilege against self-incrimination, or that she will testify as to facts exculpatory of the defendant if she is granted immunity. Her whereabouts are not known to the prosecutor, but presumably are known to the defendant. See
Schipani
v.
Commonwealth,
6. Review under G. L. c. 278, § 33E.
Although the defendant has not specifically requested it, we are obliged pursuant to § 33E to review the whole case on the law and the facts to ensure that the result is consonant with justice.
Commonwealth
v.
Tavares, ante
140, 157-158 (1982).
Commonwealth
v.
Davis,
The defendant’s principal argument is that a mistake in the identity of the assailant has occurred. Yet it is apparent from the record that if indeed Doris was the assailant, and not the defendant, the defendant had the means at her disposal to demonstrate her own innocence by establishing the
*589
guilt of her sister. Significantly, the defendant did not attempt to introduce any evidence that would have directly implicated Doris Toney. While various members of the Toney family testified, none was asked any specific questions about Doris Toney that would have shed light on whether she was in fact the assailant.
10
Moreover, the defendant introduced at trial a photograph of Doris Toney, but did not show it to either Robin Mines or Dianne Tinsley to establish that Doris Toney was indeed the murderer. The defendant gambled by omitting this evidence, and lost. Her trial was fair, and the verdict was not “against the weight of the evidence considered in a large or nontechnical sense.”
Commonwealth
v.
Cadwell,
On appeal the defendant pursues the same tactic as at trial. Nowhere does she provide the evidence necessary to establish Doris’s guilt. It is obvious, however, that if her contention is true, she has the means to do so. This selective offering of evidence renders her claim of mistaken identity lacking in credibility. Moreover, the defendant’s request that Doris Toney be granted immunity for her testimony indicates that the defendant is playing what the judge aptly called a “shell game” with the Commonwealth. This we cannot allow.
We affirm the judgment of conviction and the orders of the trial judge denying the defendant’s two motions for a new trial. The motion for an order granting use immunity to Doris Toney is also denied.
So ordered.
Notes
The testimony was conflicting regarding whether there are nine, ten or eleven sisters in the Toney family.
At trial Beane’s wife implied that she had not seen him for at least six months. There is nothing else to indicate whether others knew of his whereabouts, or whether “due diligence” was exercised to locate him and procure his testimony. See
United States
v.
Wright,
The judge instructed the jury as follows: “Now, there has been mention made by each side of evidence of the type that the law calls ‘consciousness of guilt,’ and that is evidence of an accused, a person who suspects he or she is accused, whether or not they try to hide, conceal, or to prevent their being detected or convicted. I want to caution you however, that you should never convict a person of any crime based on evidence of consciousness of guilt alone. The reason is there are equally valid reasons for an innocent person to do what he or she may do.
“Evidence, if you believe it, of consciousness of guilt may be used, however, with other evidence in the case in determining for yourselves whether or not the defendant is guilty beyond a reasonable doubt.”
Although our comments speak in terms of evidence of flight or concealment, we note that they are for the most part applicable to other types of evidence offered to prove consciousness of guilt, for example, false statements made to police, destruction or concealment of evidence, or the bribery or threatening of a witness.
E.g., Wong
Sun
v.
United States,
In light of our discussion, it would be appropriate for a judge, if requested, to caution the jury on the dangers inherent in drawing the infer *586 ence of guilt from the fact of flight. When such a request is made, the judge should explain to the jury, in appropriate language, first, that since there are numerous reasons why an innocent person might flee, flight or similar conduct does not necessarily reflect feelings of guilt. Second, he should explain that, even where a person’s flight does demonstrate feelings of guilt, it does not necessarily mean that the person is in fact guilty, because feelings of guilt are sometimes present in innocent people. See Miller v. United States, supra at 773. Such an elaboration, if given prior to the required instructions, might help the jury to understand better the required instructions.
The defendant relies on
Commonwealth
v.
Moon,
Rather, the transcript suggests that the defendant’s name was mentioned only because the police officer had talked to the defendant’s children several months earlier in connection with an unrelated incident, and therefore knew the defendant as one of the Toney sisters.
Massachusetts has a statutory procedure for the granting of immunity to witnesses. See generally G. L. c. 223, §§ 20C-20I. Under the statute, immunity may be granted to a witness appearing before the grand jury by a Justice of the Supreme Judicial Court at the request of either the Attorney General or a district attorney. G. L. c. 233, §§ 20C & 20E. A witness who testifies at trial may be granted immunity only if he has previously been granted immunity with respect to his testifying or producing evidence before a grand jury. G. L. c. 233, § 20F. This court has not found it necessary to decide whether this statutory scheme establishes the exclusive procedure by which a Superior Court judge may grant immunity to a
*588
witness. See
Commonwealth v. Simpson,
A confession made by Doris might well have been admissible under the hearsay exception for declarations against interest, provided corroborating circumstances clearly indicated its trustworthiness.
Commonwealth
v.
Carr,
