In November, 1985, the defendants were convicted of murder in the first degree, robbery while armed and masked, assault with intent to murder while armed, assault by means of a dangerous weapon, and receiving a stolen motor vehicle.2 Each has appealed from his convictions and from an order denying his motion for a new trial.
The case against the defendants depended greatly on the credibility of one William DeVincenzi, an admitted accomplice in the crimes, who testified for the Commonwealth pursuant to a written plea agreement in which the prosecution promised that it would recommend a specific sentence in return for DeVincenzi’s truthful testimony in this and other cases. We reverse the convictions because of prejudicial errors in the handling of the plea agreement that were not cured by the judge’s charge.
On April 11, 1983, during an armed robbery of Tello’s, a store in the East Boston section of Boston, a security guard was shot and killed. One year later, DeVincenzi confessed to participating in the crimes (and in many others). In December, 1984, he signed a plea agreement. Under the plea agreement, in exchange for DeVincenzi’s truthful cooperation, *259which was defined in part as the giving of “complete and honest testimony at any and all proceedings if called as a witness,” the Commonwealth agreed to accept from DeVincenzi a plea of guilty to manslaughter in connection with the security guard’s death and to recommend a sentence of from twelve to twenty years.3 If DeVincenzi were not to cooperate truthfully and a judge were so to find by a preponderance of the evidence at the time of sentencing, the Commonwealth would be free to make any sentencing recommendation it wished.
DeVincenzi gave extensive trial testimony concerning preparations for the robbery, the robbery and shooting, and the participants’ conduct following the event. The jury deliberated during four days before returning their verdicts. During that time the jury asked for further instructions on reasonable doubt, on determining the credibility of witnesses, and on circumstantial evidence. It seems a reasonable inference that the jury were concerned over the credibility of DeVincenzi’s testimony.
Before testifying to the events of April 11, 1983, DeVincenzi testified, over objection, on direct examination by the Commonwealth that he came to an agreement with the Suffolk district attorney’s office in exchange for his testimony in nineteen cases, including the ones on trial. He stated his understanding that, for his truthful testimony, the district attorney’s office would recommend a sentence of from twelve to twenty years on all his cases. DeVincenzi testified to executing the plea agreement. The judge then, over objection, admitted the plea agreement, with certain parts redacted. Again over objection, the judge permitted the prosecutor on *260direct examination to read the agreement to DeVincenzi paragraph by paragraph and ask him if what was read to him was his understanding of each paragraph. Next, the prosecutor over objection was allowed to introduce DeVincenzi’s testimony that his attorney signed a statement representing that DeVincenzi understood the agreement, that the attorney had reviewed the agreement with him, and that the attorney believed that DeVincenzi’s decision to enter into the agreement was an informed and voluntary one.4
DeVincenzi then proceeded to describe the robbery of the Tello’s store in East Boston during which, according to him, the defendant Orlandella drove a stolen brown Chrysler automobile, DeVincenzi sat in the front passenger seat, and the defendant Ciampa sat in the back seat with a sawed-off shotgun. In the course of the confrontation with the manager of the store and the security guard, who were crossing a parking lot to make a bank deposit, Ciampa shot the security guard and killed him.
The defendants advance a succession of arguments concerning the prosecution’s use of the plea agreement in connection with DeVincenzi’s testimony. They claim that admission of the agreement in evidence was in effect a representation by the prosecutor that DeVincenzi’s testimony was credible, a form of vouching by the prosecutor who was not subject to cross-examination. We disagree and conclude that, if appropriately handled, such a plea agreement does not constitute improper prosecutorial vouching for a witness. Such an agreement does, however, present the possibility that the jury will believe that the witness is telling the truth, thinking that, because of the agreement’s truthfulness requirement, the Commonwealth knows or can discover whether the witness is telling the truth. United States v. Wallace, 848 F.2d 1464, 1474 (9th Cir. 1988) (the implication is “that the prosecutor can verify the witness’s testimony *261and thereby enforce the truthfulness condition of its plea agreement”). We shall return to this problem.
We accept the rule, as do the United State Circuit Courts of Appeal generally, that testimony pursuant to a plea agreement, founded on a promise of truthful cooperation, and the plea agreement itself are admissible. See United States v. Mealy, 851 F.2d 890, 899 (7th Cir. 1988); United States v. Dadanian, 818 F.2d 1443, 1445 (9th Cir. 1987); United States v. Martin, 815 F.2d 818, 821 (1st Cir.), cert, denied, 484 U.S. 825 (1987); United States v. Townsend, 796 F.2d 158, 163 (6th Cir. 1986); United States v. Librach, 536 F.2d 1228, 1230 (8th Cir.), cert, denied, 429 U.S. 939 (1976). The trial judge must study the agreement with care, however, and eliminate prejudicial and irrelevant provisions. See United States v. Cosentino, 844 F.2d 30, 34-35 (2d Cir.), cert, denied, 109 S. Ct. 303 (1988) (the judge should “eliminate potentially prejudicial, confusing or misleading matter”), citing cases involving redaction of references to protective custody for the witness’s family and references to threats against witnesses; United States v. Brown, 720 F.2d 1059, 1073 (9th Cir. 1983) (reference to polygraph should have been deleted).5
*262The judge erred in the manner in which she handled the plea agreement. Various provisions of the agreement should have been redacted and were not. The statement that the agreement was “contingent upon the truthfulness of [DeVincenzi’s] representation to the Commonwealth that he, personally, did not shoot [the victim]” should have been redacted on request by a defendant. That statement can be read as asserting the Commonwealth’s reasoned conclusion that DeVincenzi’s representation was correct. The judge should also have deleted references in the agreement that DeVincenzi would be placed in a. program to protect his life and safety. The language was unfairly prejudicial to the defendants because it implied that the Commonwealth agreed that DeVincenzi reasonably believed his life and safety would be in jeopardy, if he testified against the defendants. See Commonwealth v. Andrews, 403 Mass. 441, 450 (1988); United States v. Arroyo-Angulo, 580 F.2d 1137, 1145 (2d Cir. 1978), cert, denied, 439 U.S. 1131 (1979). Repeated references to the witness’s obligation to tell the truth should have been deleted. See United States v. Mealy, supra at 899. Although the judge properly directed that the statement signed by DeVincenzi’s attorney should not go to the jury, over objection, she permitted the Commonwealth to obtain testimony from DeVincenzi that his attorney had signed a statement representing that DeVincenzi understood the agreement and that his attorney believed that DeVincenzi’s decision to make the agreement was an informed and voluntary one. The attorney’s hearsay statement in effect indicated that he believed DeVincenzi was telling him the truth, thus justifying his advice to DeVincenzi to plead guilty and to tes*263tify against the defendants.6 We emphasize that this opinion concerns only an agreement between a prosecutor and a witness expressed in a written plea agreement in which the Commonwealth promises a sentencing recommendation in exchange for truthful testimony.
The prejudice arising from admission of the plea agreement with damaging provisions not deleted and from DeVincenzi’s testimony concerning his attorney’s involvement with the plea agreement was not alleviated by the judge’s charge. The charge failed adequately to direct the jury’s attention to the potential influences of the plea agreement on DeVincenzi’s credibility and failed as well to dispel any implication inherent in the plea agreement, and in the presentation of DeVincenzi as a government witness, that the government knew or was warranting that DeVincenzi was telling the truth.7 The aspects of the charge most relevant to DeVincenzi’s credibility are set forth in the margin.8 That language insufficiently conveys a need for caution as to DeVincenzi’s testimony. The charge did not tell the jury to weigh DeVincenzi’s testimony with care and not to consider DeVincenzi’s guilty plea as evidence against the defendants. It did not ade*264quately focus the jury’s attention on the incentives that could have influenced DeVincenzi’s testimony. It did not warn the jury that, in entering into the agreement and presenting him as a witness, the government did not know whether DeVincenzi was telling the truth and did not emphasize that DeVincenzi’s truthfulness was solely a question for the jury to decide. Only by a cautionary instruction covering these points could the jury have been in a position to evaluate the impact of the plea agreement and testimony presented pursuant to it.
We add a few observations intended to aid trial judges handling similar circumstances in the future. We accept the general rule that on direct examination the prosecution may properly bring out the fact that the witness has entered into a plea agreement and that the witness generally understands his obligations under it. See United States v. Cosentino, supra at 33; United States v. McNeill, 728 F.2d 5, 14 (1st Cir. 1984). The timing of the admission of a plea agreement in evidence is in the judge’s discretion, if it is clear from argument or comment by the defense that, because of the plea agreement the defendant will challenge the witness’s credibility on cross-examination. United States v. Cosentino, supra. It would be discretionary with a judge to defer admission of the agreement until redirect examination, after the defendant has undertaken to impeach the witness’s credibility by showing that the witness had struck a deal with the prosecution in order to obtain favorable treatment. Any attempt at bolstering the witness by questions concerning his obligation to tell the truth should await redirect examination. Such a procedure would tend to mitigate the appearance of prosecutorial vouching that similar questions on direct examination might create. If there is ever a moment when the prosecutor should be allowed to read the agreement, paragraph by paragraph, and ask the witness successively whether each paragraph represents the witness’s understanding (as happened in the case before us), it would be during redirect examination and not during direct examination. *265A prosecutor’s position is a delicate one. The prosecutor must be free to argue that such a witness is credible, but may not explicitly or implicitly vouch to the jury that he or she knows that the witness’s testimony is true. Vouching can occur if an attorney expresses a personal belief in the credibility of a witness (Commonwealth v. Bourgeois, 391 Mass. 869, 878 [1984]), or if an attorney indicates that he or she has knowledge independent of the evidence before the jury verifying a witness’s credibility (Commonwealth v. Shelley, 374 Mass. 466, 470 [1978], S.C., 381 Mass. 340 [1980]). See United States v. Wallace, 840 F.2d 1464, 1473 (9th Cir. 1980); United States v. Martin, 815 F.2d 818, 821-822 (1st Cir.), cert, denied, 484 U.S. 825 (1987).
A prosecutor in closing argument may restate the government’s agreement with the witness and may argue reasonable inferences from the plea agreement’s requirement of truthful testimony. See United States v. Martin, supra at 822-823; United States v. Dennis, 786 F.2d 1029, 1046-1047 (11th Cir. 1986), cert, denied, 401 U.S. 1037 (1987). If, however, a prosecutor goes beyond the terms and circumstances of the plea agreement and suggests that the government has special knowledge by which it can verify the witness’s testimony, reversible error may occur. See United States v. Brown, 720 F.2d 1059, 1072, 1075 (9th Cir. 1983); United States v. Roberts, 618 F.2d 530, 534, 536-537 (9th Cir. 1980), cert, denied, 452 U.S. 942 (1981). Certain arguments of a prosecutor to the jury would clearly be improper. See United States v. Wallace, supra at 1474 (“that would not have been the truth,” and “she told the truth” were improper vouching); United States v. Martin, supra at 822 (“they told you the truth,” disapproved); United States v. Roberts, supra at 533 (closing argument that a detective had monitored the witness’s testimony, impermissible vouching). On the other hand, a prosecutor may properly point out that an agreement seeking only the truthful cooperation of the witness does not give the witness any special incentive to lie. United States v. Arroyo-Angulo, 580 F.2d 1137, 1147 (2d Cir. 1978).
*266As we have noted, the plea agreement by itself could be viewed as an implied representation by the government that the witness’s testimony will be truthful. The implied representation of credibility far exceeds any implication of credibility arising from simply calling a witness to testify for the Commonwealth under oath. Because of the possible improper influences on a jury that could develop from hearing testimony given pursuant to a written plea agreement that offers substantial benefits to a witness but only if the witness tells the truth, courts have generally determined that, although a jury may hear such a witness and receive as an exhibit a copy of the agreement, the judge must specifically and forcefully tell the jury to study the witness’s credibility with particular care. See Untied States v. Mealy, 851 F.2d 890, 900 (7th Cir. 1988) (witnesses’ testimony “must be considered with caution and great care. Moreover, their guilty plea is not to be considered as evidence against the defendants”); United States v. Shaw, 829 F.2d 714, 718 (9th Cir. 1987), cert, denied, 485 U.S. 1022 (1988) (in the circumstances, “[i]t would have been better if the trial court had given an instruction that the reference to truthfulness in the plea agreement does not mean that the government has a way of knowing that the testimony is truthful,” but the judge did tell the jury that they should examine the benefited witness’s testimony “with greater caution than that of ordinary witnesses”); United States v. Dailey, 759 F.2d 192, 196, 200 n.8 (1st Cir. 1985) (the jury should “be specifically instructed to weigh the accomplice’s testimony with care”); United States v. Sims, 719 F.2d 375, 378 (11th Cir. 1983), cert, denied, 465 U.S. 1034 (1984) (trial judge dispelled any suggestion of vouching by instructing the jury to keep in mind that testimony given pursuant to an immunity agreement “is always to be received with caution and weighed with great care”).
We do not prescribe particular words that a judge should use. We do expect, however, that a judge will focus the jury’s attention on the particular care they must give in evaluating testimony given pursuant to a plea agreement that is contingent on the witness’s telling the truth.
*267Because there must be a new trial, we consider issues argued on appeal that are likely to reappear, (a) If evidence of threats made by third parties to certain witnesses is offered to show Orlandella’s consciousness of guilt, that evidence should not be admitted for that purpose unless the Commonwealth presents evidence that the threats were made with Orlandella’s knowledge, consent, or authorization. See Commonwealth v. Min Sing, 202 Mass. 121, 127 (1909); Commonwealth v. Robbins, 3 Pick. 63, 63 (1825). Even then, the judge should consider whether the probative value of evidence of threats by third persons on the consciousness of guilt question is outweighed by its prejudicial effect. See Commonwealth v. Leo, 379 Mass. 34, 41 (1979). (b) We see no impropriety in trying the defendants jointly, (c) The murder indictments were properly given to the jury on the theory of extreme atrocity or cruelty where the victim was hit with a blast from a shotgun from a distance of several feet and did not die immediately. See Commonwealth v. Glass, 401 Mass. 799, 803 (1988). (d) Our failure to address other issues does not mean that the defendants’ undiscussed appellate arguments are without merit but simply that the issues will not arise again or are not likely to arise in the same form. Asserted problems in the judge’s charge not discussed in this opinion will presumably be avoided by jury instructions crafted by the judge who retries the case. For example, at retrial the jury should not be told that they may infer a defendant’s consciousness of guilt if they disbelieve the defendant’s alibi witnesses. Also, at retrial the language of Commonwealth v. Rodriguez, 378 Mass. 296, 302 (1979), should not be used when discussing how the jury should assess the testimony of any defense witness who testifies that the men in the vehicle leaving the scene of the crime were not the defendants. The Rodriguez opinion concerns the appropriate instruction to be given concerning the possibility of mistaken identification of a defendant by prosecution witnesses.
In discussing the grounds on which we determine that admission of the plea agreement and certain testimony concern*268ing it constitute reversible error, the dissent states its view that, in certain instances, appellate rights were not preserved at trial or an issue was not specifically argued on appeal. Our function under G. L. c. 278, § 33E (1988 ed.), in reviewing a conviction of murder in the first degree is to consider, not only issues clearly preserved for appellate review, but also issues apparent on the record (see Commonwealth v. Brown, 376 Mass. 156, 166-168 [1978]; Commonwealth v. Corcione, 364 Mass. 611, 618 [1974]), to determine whether there is a substantial likelihood of miscarriage of justice. For example, in Commonwealth v. Callahan, 380 Mass. 821, 822 (1980), this court rejected all the arguments advanced on appeal by a defendant convicted of murder in the first degree, and then, based on its independent review of the record, identified an error, not argued below (id. at 826), that required the court to order a new trial.
In the course of that portion of the trial that concerned the admission of the plea agreement and testimony concerning it, one or more defense counsel objected to the witness testifying to the content of the agreement; to the self-serving quality of the agreement’s references to truthfulness; to the bootstrapping quality of the statement that the benefits to DeVincenzi of the agreement depended on the fact DeVincenzi did not shoot the victim; to reading the agreement to the witness; and to the hearsay representations inherent in testimony concerning the involvement of DeVincenzi’s counsel in the execution of the plea agreement. At another point counsel sought, perhaps belatedly, to raise a different but unidentified objection but was barred from doing so.
Surely trial counsel could have done a better job. They could have moved for the redaction of specific portions of the agreement after the judge ruled that the agreement in general was admissible. Indeed a pretrial motion along the same lines would have been appropriate. Perhaps appellate counsel should have focused on the inappropriateness of specific portions of the agreement other than those they thought inappropriate. In any event, we regard as fully before us the question whether there should be a new trial because of the *269errors that we have identified and viewed collectively as prejudicial.
As to a crime that once carried the penalty of death and that now alone calls for the imposition of a sentence of life imprisonment without the possibility of parole, a special duty has been assigned to us under G. L. c. 278, § 33E. We must disregard omissions of counsel if justice requires us to order a new trial. Such an appellate process can rightly be troublesome to the trial judge because it does not mean in all instances in which we order a new trial that the trial judge has erred in any traditional (or even nontraditional) sense. That problem is, however, inherent in the process required of us under § 33E.
The judgments are reversed, the verdicts set aside, and the cases are remanded to the Superior Court for retrial.
So ordered.
Ciampa was also convicted of unlawfully carrying a shotgun on his person.
The Commonwealth also agreed (a) to recommend concurrent sentences on other charges pending against DeVincenzi, (b) to endeavor to have DeVincenzi serve his sentence in an appropriate Federal institution, (c) to acknowledge DeVincenzi’s truthful cooperation to other governmental agencies and courts, (d) to try to have charges pending in New Hampshire against DeVincenzi disposed of on a concurrent basis, and (e) to use available programs within lawful limits to protect DeVincenzi’s life and safety during confinement.
The agreement as it went to the jury did not contain the attorney’s signed statement, and a reference to the results of a polygraph examination was deleted.
Some Federal courts have accepted the admissibility of plea agreements that were not only contingent on the witness’s truthful testimony but also were contingent on the government’s general satisfaction with the witness’s testimony. See United States v. Spector, 793 F.2d 932, 934, 936-937 (8th Cir. 1986), cert, denied, 479 U.S. 1031 (1987) (the agreement provided “[t]he more important we deem that information and cooperation [in solving and prosecuting crimes], the more likely the reduction of charges and [the informant’s] sentencing risk”); United States v. Dailey, 759 F.2d 192, 197, 200-201 (1st Cir. 1985) (government’s recommendation for sentencing will be influenced by “the value to the government” of the witness’s cooperation; such a contingent plea agreement “should be reserved for exceptional cases, such as this one, where the value and extent of the accomplice’s knowledge is uncertain but very likely to be great”); United States v. Waterman, 732 F.2d 1527, 1531 (8th Cir.), vacated en banc, id. at 1533 (1984) (four-to-four decision) (affirming a conviction based on testimony of witness whose subsequent treatment by the government was contingent on the success of the prosecution), cert, denied, 471 U.S. 1065 (1985). We need not go so far in deciding this case because the plea agreement here *262did not depend on the results of the prosecution or on the Commonwealth’s satisfaction with the witness’s testimony.
Testimony pursuant to a plea agreement made contingent on obtaining an indictment or a conviction, as a result of the witness’s testimony, would presumably present too great an inducement to lie, would not meet the test of fundamental fairness, and would not be admitted. See United States v. Dailey, supra at 201; United States v. Waterman, supra at 1531.
The better course would be also to delete any signature of the prosecutor or other representative of the Commonwealth from the agreement as admitted in evidence.
The defendants objected to aspects of the charge concerning DeVincenzi sufficiently to put the judge on notice of the need for a special instruction concerning DeVincenzi. We need not consider whether the objections were sufficiently focused to preserve as appellate issues various challenges to the jury instructions. Our holding is that the prejudicial admission of portions of the plea agrément was not cured in the judge’s charge.
“You should give the testimony of each witness such weight as in your good judgement it is fairly entitled to receive.” The fact that a person was an accomplice “in itself raises a question of credibility .... The testimony of an accomplice need not be corroborated. In other words, you need not have other evidence, if you find beyond a reasonable doubt that you believe the testimony of William DeVincenzi.... Whether you should believe the testimony of an accomplice rests in your good judgment based upon all the evidence before you .... You may consider the [plea] agreement and any hopes the witness may have as to future advantages in judging his credibility.”