The defendant appeals from the judgment of conviction, following a jury trial, of three counts of sale of narcotics in violation of General Statutes § 21a-277 (a). The defendant’s sole claim on appeal is that prosecutorial misconduct deprived him of a fair trial. We reverse the judgment of conviction and order a new trial.
The jury could reasonably have found the following facts. On February 23, 1995, Sergeant Dennis Coyle of the statewide narcotics task force, in conjunction with law enforcement officers from the Waterbury police department and the Federal Bureau of Investigation (FBI), conducted an undercover operation in the north end of Waterbury in which police officers, posing as *182buyers, purchased narcotics from street dealers. The operation targeted several areas known for heavy drug traffic.
During the late afternoon, Detective Nicholas DeMat-teis of the Waterbury police department and FBI Agent William Reiner, Jr., were in an undercover vehicle in the vicinity of Hawkins and Adams Streets. Both officers observed what they characterized as drug related activity. Their attention was specifically drawn to a black male of average build, wearing a striped jacket with a blue hooded sweatshirt. Because DeMatteis believed that this man was conducting a drug transaction, he directed statewide narcotics task force agents John Cole, Laura Wigglesworth, and Thomas Bennett to make purchases from any persons selling drugs in that area.
Cole drove down Hawkins Street and spotted the same individual standing on the sidewalk with several other men. The defendant approached Cole’s vehicle. Cole asked him, “Who’s got those twenties,” referring to $20 bags of crack cocaine. The defendant handed Cole two small green plastic bags containing a white rock-like substance that Cole recognized as crack cocaine. Cole gave the defendant $40 and drove off. Wigglesworth and Bennett then drove to the same location, where the defendant approached their car and handed each officer one bag of the same substance. Following these transactions, DeMatteis and Reiner drove down Hawkins Street to get a closer look at the defendant.
Thereafter, all of the participating officers met with Coyle a few blocks away. Cole, Wigglesworth and Bennett each turned over the green plastic bags to Coyle, who secured them as evidence and sent them to the state toxicology laboratory. Analysis revealed that each bag contained nonsalt cocaine. After a jury trial, the defendant was convicted of three counts of sale of *183narcotics and sentenced to concurrent fifteen year prison terms on each count.
The defendant claims that misconduct by the assistant state’s attorney prosecuting the case deprived him of a fair trial in violation of the due process clause of the fourteenth amendment to the United States constitution. We agree. The cumulative pattern of prosecu-torial misconduct, frequent and severe, falls into six categories of proscribed behavior: (1) expressing opinions as to the credibility of witnesses; (2) arguing to the jury that in order to acquit the defendant it must necessarily find that the officers testifying for the state committed perjury; (3) testifying as an expert witness; (4) misallocating the burden of proof; (5) appealing to the emotions, passions, and prejudices of the jurors; and (6) deliberately violating the rulings on a motion in limine.
I
A prosecutor may not express his own opinion, either directly or indirectly, as to the credibility of his witnesses. United States v. Modica, 663 F.2d 1173, 1178-79 (2d Cir. 1981); United States v. Drummond, 481 F.2d 62, 63-64 (2d Cir. 1973); State v. Williams, 204 Conn. 523, 541-44, 529 A.2d 653 (1987). Similarly, counsel may not submit to a jury that a witness has testified truthfully. State v. Oehman, 212 Conn. 325, 336, 562 A.2d 493 (1989). A prosecutor’s voucher for the credibility of his witnesses is dangerous primarily because “the prosecutor’s opinion carries with it the imprimatur of the Government and may induce the jury to trust the Government’s judgment rather than its own view of the evidence.” United States v. Young, 470 U.S. 1, 18-19, 105 S. Ct. 1038, 84 L. Ed. 2d 1 (1985).
The defendant complains of repeated instances in which the prosecutor, despite several defense objections and subsequent admonishments from the trial *184court, vouched for the credibility of her witnesses:1 “I would submit to you [the jury] that all of these officers are extremely honest”; “I would submit to you that there’s no evidence that they testified] dishonestly”; “Detective DeMatteis was very honest with you”; “[the officers] all told you honestly what they saw.” The prosecutor also told the jury that the state’s attorney’s office would not “stand by” and let a state’s witness testify falsely as to the defendant’s identity.
The state argues that the defendant induced the collective responses from the prosecutor when he first stated that DeMatteis had a motive to lie and called him a “bald-faced liar.” The response to this comment, however, should have been limited to DeMatteis. The prosecutor improperly expressed her opinions as to the credibility of all the officers in numerous other instances of vouching. By personally vouching for the integrity of each of her identification witnesses, the prosecutor improperly put the weight of her office into the balance against the defendant.
II
Prosecutors have been admonished to avoid statements to the effect that, if the defendant is innocent, government agents must be lying. United States v. Richter, 826 F.2d 206, 208 (2d Cir. 1987); People v. Yant, 75 App. Div. 2d 653, 654, 427 N.Y.S.2d 270 (1980) (holding prosecutor improperly argued that to acquit defendant jury would have to find that officers testifying for state had committed perjury).
The defendant cites several comments in which the prosecutor argued that, in order to acquit the defendant, *185the jury must necessarily believe that her witnesses were perjuring themselves: “And think about the witnesses you have to compare. You have six officers, six officers who don’t have an interest in the case, six officers who don’t have this type of a record.” “Is it reasonable that six officers [would] swear under oath they know absolutely that [this] is the man, if they weren’t absolutely certain? Absolutely not.” “I submit to you that in order to believe the defendant’s version, what he’s asking you to do is believe that these officers, six officers, would come in and for no reason whatsoever lie and perjure themselves and subject themselves to all types of penalties.”
The jury was not required to find that the officers intentionally lied in order to acquit the defendant, nor was it required to believe the defendant’s testimony in order to doubt the accuracy of the state’s identification witnesses. Thus, the prosecutor improperly suggested that a finding for the defendant’s version of the facts was tantamount to a finding that the police officers had committed perjury.
Ill
A prosecutor, in fulfilling his duties, must confine himself to the evidence in the record. State v. Binet, 192 Conn. 618, 631, 473 A.2d 1200 (1984). “[A] lawyer shall not . . . [a]ssert his personal knowledge of the facts in issue, except when testifying as a witness.” ABA Model Code of Professional Responsibility DR 7-106 (C) (3) (1980). Statements as to facts that have not been proven amount to unsworn testimony, which is not the subject of proper closing argument. State v. Williams, supra, 204 Conn. 544.
At trial, the defendant asked why the outsides of the plastic bags bought by undercover officers had not been tested for fingerprints. The state did not introduce an expert to testify that testing the bags would have been *186impossible. Instead, the prosecutor substituted her opinion as to the feasibility of such testing for that of an expert witness: “Well, now, the drugs [in the bag] have already been tested, so how many people do you think have handled this one little envelope. I can tell you a lot of people have handled it. You think we’re going to get fingerprints on this two weeks ago when the defendant just decided to give the name [Robert Arline as the man who sold the drugs].”2 The prosecutor improperly testified as to the feasibility of fingerprint testing instead of presenting a witness to testify that the manner in which the police handled the plastic bags would have rendered fingerprint testing impossible or inconclusive.
IV
It is axiomatic that the state must prove every fact necessary to constitute the crime with which a defendant is charged beyond a reasonable doubt. In re Winship, 397 U.S. 358, 364, 90 S. Ct. 1068, 25 L. Ed. 2d 368 (1970). Once an alibi defense is raised in Connecticut, the state bears the burden of disproving it. State v. Bryant, 202 Conn. 676, 703, 523 A.2d 451 (1987).
The defendant raised an alibi defense at trial and also argued that Robert Arline, a known drug dealer, was the man in the surveillance photographs taken by the undercover officers. The defendant presented witnesses to corroborate his identification of Arline. In so doing, the defendant showed the surveillance photographs, provided to him by the state, to the testifying witnesses.
Despite the defendant’s objections that he did not have the burden of proving his alibi defense and the trial court’s rulings that the state was misrepresenting *187its burden of proof to the jury, the prosecutor repeatedly maintained that the defendant purposefully and selectively showed unclear surveillance photographs to the jury because he had no better evidence in support of his alibi and stated: “I’m going to submit to you that the reason they chose to submit the [photographs] they did is because they’re the ones that are the most difficult to really see . . . .” The prosecutor stated further: “I’m going to submit to you . . . that counsel is really stretching here, and the reason he’s stretching is because he doesn’t really have anything else to go with . . . .” She also stated that the defendant has failed to present “any evidence to support that he was anywhere else.” The prosecutor improperly attempted to distort the state’s burden of proof and to allocate to the defendant the burden to disprove his alibi.
V
A prosecutor may not appeal to the emotions, passions, and prejudices of the jurors. United States v. Modica, supra, 663 F.2d 1181; State v. Couture, 194 Conn. 530, 564-65, 482 A.2d 300 (1984). Such an appeal should be avoided because it “invites the jury to decide the case, not according to a rational appraisal of the evidence, but on the basis of powerful and irrelevant factors which are likely to skew that appraisal.” State v. Williams, supra, 204 Conn. 546. Similarly, a prosecutor should not inject extraneous matters into the case that divert the jury from its duty to decide the case solely on the evidence. Id., 547; 1 A.B.A., Standards for Criminal Justice (2d Ed. 1980) c. 3, standard 3-5.8 (d).
The defendant complains of a series of comments in which the prosecutor argued that the officers risked their personal safety to secure the defendant’s arrest: “You heard that [the officers] were putting their lives on the line. I think as just members of society, I think your common sense would tell you that they’re putting *188their lives on the line.” Undaunted by defense objection and the trial court’s ruling that there was no evidence in the record to support a finding that the officers were in any danger, the prosecutor nonetheless immediately repeated the remarks: “You heard their safety was always a concern . . . this isn’t, again, fun and games. This is real life, ladies and gentlemen, real life.”
By diverting the jurors’ attention to matters that were irrelevant and to those not supported by the evidence, the prosecutor improperly asked the jurors to determine the defendant’s guilt with the emotional predicate that they were “just” and good members of society for whom the officers were “putting their lives on the line.”
VI
Pursuant to a motion in limine, the trial court specifically ruled that state’s witnesses were precluded from (1) referring to previous investigations of the defendant, and (2) referring to how they knew the defendant.
The defendant asserts that the prosecutor repeatedly and flagrantly violated the motion in limine orders. In perhaps the most conspicuous violation, the prosecutor asked DeMatteis how many times he had previously dealt with the defendant. Additionally, in her summation, the prosecutor argued: “You heard from Detective DeMatteis that he knows this individual and you heard that he knows him from his work. Ladies and gentlemen, where does he work? He works for the Waterbury police department. What unit does he work in? He works in the tactical narcotics team.” Undaunted by the defendant’s objection and the trial court’s curative instruction, the prosecutor immediately argued: “You heard that Detective DeMatteis works for the Waterbury police department. You heard that’s how he knows this individual.” (Emphasis added.) These remarks illustrate that the prosecutor deliberately violated the trial court’s specific rulings on the motion in limine.
*189VII
Our review of the record indicates that the defendant did not properly preserve some of the claims at trial for which he now seeks review. Because the defendant objected and requested curative instructions with enough frequency to alert the trial court to the persistent misconduct, however, and because the record adequately supports that he has been deprived of a fundamental constitutional right and a fair trial, we will review the unpreserved portions. State v. Golding, 213 Conn. 233, 239-40, 567 A.2d 823 (1989); State v. Evans, 165 Conn. 61, 70, 327 A.2d 576 (1973); see State v. Pelletier, 196 Conn. 32, 34, 490 A.2d 515 (1985). Our review of the record discloses that the multiple instances of blatantly egregious conduct now challenged do not constitute an isolated instance of misconduct, but a pattern repeated through the trial.
The defendant claims that egregious prosecutorial misconduct deprived him of his constitutional right to a fair trial under the due process clause of the federal constitution. In analyzing this claim, we ask whether the prosecutor’s conduct “so infected the trial with unfairness as to make the resulting conviction a denial of due process. Darden v. Wainwright, 477 U.S. 168, 181, 106 S. Ct. 2464, 91 L. Ed. 2d 144 (1986), quoting Donnelly v. DeChristoforo, 416 U.S. 637, 94 S. Ct. 1868, 40 L. Ed. 2d 431 (1974) .... We do not focus alone, however, on the conduct of the prosecutor. The fairness of the trial and not the culpability of the prosecutor is the standard for analyzing the constitutional due process claims of criminal defendants alleging prosecutorial misconduct. State v. Palmer, 196 Conn. 157, 163, 491 A.2d 1075 (1985), quoting State v. Ubaldi, 190 Conn. 559, 562, 462 A.2d 1001, cert. denied, 464 U.S. 916, 104 S. Ct. 280, 78 L. Ed. 2d 259 (1983) . . . .” (Citations omitted; internal quotation marks omitted.) State v. Williams, supra, 204 Conn. 539-40.
*190In determining whether prosecutorial misconduct was so serious as to amount to a denial of due process, we focus on several factors: (1) the extent to which the misconduct was invited by defense conduct or argument; (2) the severity of the conduct; (3) the frequency of the conduct; (4) the centrality of the misconduct to the critical issues of the case; (5) the strength of the curative instructions adopted; and (6) the strength of the state’s case. Id., 540.
We have carefully examined the record and conclude that the course of prosecutorial misconduct was in deliberate violation of those matters explicitly and implicitly precluded by the ruling on the motion in limine. With the exception of a response to a single comment, the misconduct was not invited by the defendant’s conduct or triggered by the defendant’s argument. The misconduct bore directly on the critical issue of the defendant’s credibility and the believability of his alibi defense. The prosecutor’s conduct was frequent and severe, and she ignored repeated warnings from the trial court.
We note that the court gave some of the defendant’s curative instructions and ordered some of the objectionable matter stricken from the record. The cumulative effect of the prosecutor’s misconduct throughout the trial was so serious, however, that no curative instruction could reasonably have been expected to remove its prejudicial impact. State v. Fullwood, 194 Conn. 573, 585, 484 A.2d 435 (1984). In this case, the curative measures utilized by the court, consisting of occasional directions to the jury to disregard the remarks of the assistant state’s attorney and of brief charges to the jury were insufficient to eliminate the accumulated harm created by the course of prosecutorial misconduct. Because of the severity and frequency of the misconduct, this is not a situation where we can safely rely on the presumption that the jury will follow the court’s *191instructions. See State v. Williams, supra, 204 Conn. 549. Although we generally give great weight to a trial court’s effort to eliminate prejudice through a curative instruction, “ ‘[i]f you throw a skunk into the jury box, you can’t instruct the jury not to smell it.’ ” United States v. Garza, 608 F.2d 659, 666 (5th Cir. 1979), quoting Dunn v. United States, 307 F.2d 883, 886 (5th Cir. 1962).
This is not a case in which the state’s evidence is so strong that we can say that the misconduct constituted harmless error. The defendant steadily maintained that Arline was the person in the surveillance photographs and disputed all of the state’s identification testimony. The defendant’s credibility and the believability of his alibi defense were thus pivotal issues for the jury’s determination. The pervasive misconduct directed at the defendant’s credibility and the veracity of his alibi defense was pronounced and persistent, and we cannot dismiss its cumulative effect on the jury as inconsequential. We conclude that the defendant was denied a fair trial in violation of his federal constitutional right to due process of law.
The judgment is reversed and the case is remanded for a new trial.
In this opinion HENNESSY, J., concurred.
Providing an exhaustive list of the misconduct that pervaded this trial would be impractical; we have included a representative sample of the misconduct alleged in some of the defendant’s claims. See State v. Williams, supra, 204 Conn. 523. The defendant’s additional claims of prosecutorial misconduct are fully discussed in the dissent that follows.
We note that this argument is also contrary to the evidence adduced by the state that the officers put the plastic bags inside envelopes immediately following the transactions.