(dissenting). I respectfully dissent from the

holding of the majority that there must be a new trial. Their conclusion is based on certain conduct of the prosecutor which they consider to be egregious, purported error by the judge in regard to the admission of certain evidence, and challenges by the prosecutor of prospective jurors which the majority perceive to have been a violation of Commonwealth v. Soares, 377 Mass. 461 (1979). I believe that any misconduct by the prosecutor was harmless and cured by instruction to the jury by the judge, that the error by the *133judge was harmless, and that the record is inadequate to show and in any event does not show a Soares violation.

Under the heading “[pjrosecutorial error,” the majority opinion cites a single statement made by the prosecutor, early in the trial, as one reason for their conclusion that the convictions must be reversed. The utterance by the prosecutor, which of course should never have been made, vouched for the credibility of the Commonwealth’s witnesses. Defense counsel objected to the statement and moved for a mistrial, which was denied by the judge. The judge, instead, gave an instruction to the jury to disregard the statement. The majority state that the judge’s instruction “scarcely came to grips with the problem.” But that observation is at odds with the reaction of defense counsel, who did not object to the judge’s instruction. Their conduct is of signal importance for they, unlike us, were present and could actually hear and assess the impact of the instruction. By contrast, our knowledge of the worth of the instruction is limited to what we may ascertain from the printed page. In view of their vigilance and aggressiveness in challenging the conduct of the trial throughout its duration,1 one can only conclude from their silence in the face of the judge’s instruction that they were satisfied that the trial was back on an even course by the manner of the judge’s delivery of the instruction, its content and its reception by the jury.2 In addition, weeks after the comment by the prosecutor, the judge in his closing instructions informed the jurors that they were the sole judges of the credibility of the witnesses.

*134Under the same heading, the majority opinion cites other instances or purported prosecutorial misconduct that occurred during the long trial. None of these examples was the subject of objection, and apparently the majority do not hold that even considered cumulatively they require a new trial. In any event, any excess by the prosecutor in his closing argument was cured by the judge in his charge to the jury.

The majority find reversible error in the admission in evidence of a marked photograph. A detective of the Three Rivers (Canada) police department testified that he had received the picture from the Springfield police with an inquiry whether he recognized any of the faces in the picture. The inked and intialized identification of Gagnon and Bourgeois had been his response. Timely objection to the introduction of the photograph was made by defense counsel on the ground that the picture was not necessary and would show “that Bourgeois and Gagnon were known to the Canadian police and inferably, were bad men.” I agree with the majority that the introduction in evidence of the marked photograph was error,3 but I believe that it was harmless error in light of the overwhelming evidence against the defendants. Commonwealth v. Mandeville, 386 Mass. 393, 400 (1982).

The majority find that there was also a violation of the principles enunciated in Commonwealth v. Soares, 377 Mass. 461 (1979).4 In Soares, the Supreme Judicial Court held that the exercise of peremptory challenges to exclude members of certain discrete groups from the jury “solely on *135the basis of bias presumed to derive from [their] membership in the group” violated the defendants’ right to a trial before a jury of their peers as guaranteed by art. 12 of our Declaration of Rights. Id. at 488. The court included “national origin” as part of “those generic group affiliations which may not permissibly form the basis for juror exclusion,” id. at 488-489, and I agree with the majority that persons who are French-Canadians are members of a discrete group for the purposes of Soares. My disagreement with the majority is two-fold: (1) Soares does not apply because of the limited record in this case; and (2) if Soares does apply, there was no violation.

In Commonwealth v. Soares, supra, the court addressed the problem of retroactivity and fashioned a two-prong test that had to be met before the Soares principles would be applied. The court held that the rule in Soares applies to a case, (1) that was pending on direct appeal on March 8, 1979, the date of the Soares decision, and (2) where the record is adequate to raise the issue. 377 Mass. at 493 n.38.5 The trial in this case concluded some 270 days before March 8, 1979, and was on direct appeal when Soares was decided; therefore, the first prong of the test is satisfied. It is my view, however, that the record is inadequate to raise the issue.

In order properly to assess whether there was a Soares violation, it is necessary to obtain from the record information with regard to certain factors. These factors “include not only the numbers and percentage of group members excluded, but also common group membership of the defendant and the jurors excluded, and of the victim and remaining jurors.” Commonwealth v. Robinson, 382 Mass. 189, 195 (1981).

*136The record discloses that the defendants are of French-Canadian ancestry. The victims in the indictments are two bank tellers and a police officer. The record is silent as to their nationality. Of the 105 prospective jurors who were declared to be satisfactory by the judge, the Commonwealth challenged forty-three persons, and the defendants exercised forty-six challenges.6 There were sixteen persons sworn as jurors. However, there is nothing in the record as to the ancestry of the jurors. I believe, therefore, that the record is not adequate to raise the issue before us. Commonwealth v. Mahdi, 388 Mass. 679, 690 (1983).

Even if there were an adequate record, I am of the opinion that there was no Soares violation. The crux of the majority’s holding that there was such a violation is that “[tjhere were twenty-three persons with names that were arguably French called from the venire, and the prosecution challenged nineteen of them” (supra at 118). I agree with the majority that names are less than a “totally reliable badge of ethnic identity” (supra at 119); and that is the reason that I rely on the record. Of the twenty-three persons with “arguably” French names, there is nothing in the record as to the ancestry of eleven of them. But as to twelve of the twenty-three persons, the record indeed shows that *137they are of French or French-Canadian ancestry.7 Of these twelve persons, the majority agree that the Commonwealth was correct in challenging two of them. Of the remaining ten, the Commonwealth stated that it was satisfied with three prospective jurors who spoke French, two of whom had close ties to French Canada.8 But each defendant challenged these prospective jurors. The actions of the defendants in challenging three individuals, one of known French and two of known French-Canadian ancestry, are astonishing in view of the claims made by the defendants on appeal that they were denied a fair jury because of the actions of the prosecutor in excluding persons with French surnames from the jury.

I repeat that the record is inadequate for us to decide the issue. Further, because of the actions of the defendants in challenging three persons of known French or French-Canadian ancestry, I believe it would be “a perverse misuse of the [Scores] doctrine to apply it” to this trial. Commonwealth v. Whitehead, 379 Mass. 640, 646 (1980).

Highly competent police work resulted in the arrest and conviction of the defendants of armed robbery while masked of an employee of a bank,2 armed assault with intent to murder,3 attempted murder,4 assault and battery on a police officer,5 and assault and battery by means of a dangerous weapon.6 Regrettably, the trial was sufficiently tainted with error to require reversal of the judgments and a new trial.

We sketch an outline of facts which the jury could have found, leaving details to discussion of the particular points on appeal to which they are relevant. On June 10, 1977, shortly after 10 a.m., three men, gloved and masked, robbed a branch of the Shawmut First Bank in Springfield. Two, at least, were armed. One vaulted the tellers’ counter, and the other two joined him there. The robbers took money out of the teller drawers and made their escape, with about $126,000, by a back or side door to an alleyway. *113While the robbery was in progress — it did not take more than three minutes — the branch manager activated a holdup alarm.

The first officer to respond was Edward Petrick, Jr., driving a marked cruiser. Petrick arrived on the scene as the branch manager emerged; the manager pointed to an alley, from which a sedan was emerging. In that vehicle were three men, one of whom was pulling off a stocking mask. Petrick gave chase in his cruiser and was answered with gunfire. At one point the getaway car had to stop in a line of traffic and two men, whom Petrick later identified as Gagne and Bourgeois, alighted and directed a fusillade of gunfire at Petrick. When Petrick’s car, too, came to a stop, he scrambled out and was wounded by gunfire.

These events were scarcely calculated to avoid attention, and, indeed, several witnesses observed the escape car, a Ford LTD, and noted its license plate number. Two robbers switched from the LTD to a Ford Mustang; that car’s license plate was also noted. Each plate evidenced a Quebec registration. Through motel registrations, the trail led to Bourgeois and Gagnon, who were Canadians. Further investigation led to Gagne and one Paquette, who is not a defendant in this case.

On February 4, 1978, Corporal Andre Dube, a Quebec police officer, searched a locker and apartment at 714 Sicotte Street, in the city of Quebec, and found guns, a road map of Springfield, a red knitted cap with two holes for eyes, a bullet proof vest, newspaper clippings about the Springfield holdup, over $1,000 in American money, photographs and other documents and items which linked the owner of the apartment to the Springfield affair. The apartment was leased to one Gilíes DeNeuville which, it turned out, was an alias of the defendant Gagnon.

In addition to Petrick’s in-court identification, a bystander, Maurer, identified Gagnon in court, and a motel maintenance man identified Gagne in court. Over $3,000 in American money found in the possession of Gagne and Pa-*114quette bore serial numbers traceable to the Springfield bank. We turn to the individual issues.

1. Prosecutorial error. During cross-examination of Officer Petrick on the tenth day of trial on which evidence was received, trial counsel for Gagne, Mr. Serota, probed for inconsistencies between Petrick’s trial testimony and a written statement Petrick had made earlier. Petrick was an important witness for the prosecution on the issue of identification. The following colloquy occurred.

Mr. Serota: “From the comma [referring to a page of Petrick’s statement], T tried to run them down, and at the same time call in the information to the Station.’ Now as to that phrase in your statement is that true?”

Mr. Ryan (the district attorney): “I object.”

The court: “The grounds, Mr. Ryan?”

Mr. Ryan: “I object to the statement, is that true. I would assume any witness we put on here —”

Mr. Serota: “I object to that statement.”

Mr. Ryan: “— we vouch for their credibility, and I don’t think that that’s the proper way to characterize a question.”

The court: “Side bench.”

At the side bar defense counsel objected vociferously to the district attorney’s vouching before the jury for the credibility of his witnesses, and Mr. Serota moved for a mistrial. Mr. Gordon, who represented Gagne, specifically requested that the jury be instructed that it was an improper remark. At the conclusion of the side bar conference, the judge said: “The jury will disregard comments of counsel completely. The question will go out, and if you heard an answer [none had been made], that goes out.”

Assertion of personal opinion as to the credibility of a witness or as to the guilt of an accused is prohibited by S.J.C. Rule 3:07, DR 7-106(C)(4), 382 Mass. 787 (1981), previously appearing as S.J.C. Rule 3:22, DR 7-106(C)(4), *115359 Mass. 822 (1971). Commonwealth v. Smith, 387 Mass. 900, 906 (1983). For counsel to state a belief as to the credibility of a witness “is peculiarly unfortunate if one of them has the advantage of official backing.” Greenberg v. United States, 280 F.2d 472, 475 (1st Cir. 1960). See also Commonwealth v. DeChristoforo, 360 Mass. 531, 545-547 (1971) (Tauro, C.J., dissenting). Compare Orebo v. United States, 293 F.2d 747, 749-750 (9th Cir. 1961), cert. denied, 368 U.S. 958 (1962).

Often, when improper statements of belief are argued, the question is whether, in context, the prosecutor was stating a personal opinion or commenting acceptably on the evidence. See, e.g., Commonwealth v. Stone, 366 Mass. 506, 516 (1974); Commonwealth v. Bradshaw, 385 Mass. 244, 275 (1982). Here, by contrast, there was a wholesale vouching for the credibility of all the prosecution’s witnesses. “The point is that the representative of the government approaches the jury with the inevitable asset of tremendous credibility — but that personal credibility is one weapon he must not use.” United States v. Gonzalez Vargas, 558 F.2d 631, 633 (1st Cir. 1977). That asset is the more potent where, as here, the prosecutor is the district attorney himself, a figure likely to be known to the jurors. As in the Gonzalez Vargas case, there are none of the extenuating circumstances that cause courts to shrug off an excess of counsel, viz., provocation by opposing counsel (Mr. Serota’s gambit of attacking Petrick’s credibility by pointing out inconsistencies with prior statements was hardly an unusual tactic), “absence of an objection, or a timely curative instruction directed particularly to the prosecutor’s comments.” Ibid. “The jury will disregard comments of counsel completely,” scarcely came to grips with the problem. Compare Commonwealth v. Hoppin, 387 Mass. 25, 28-32 (1982), where strong and precise instructions, although somewhat belated, did not neutralize a prosecutor-ial error. We are constrained to reverse and “do so unhappily.” United States v. Gonzalez Vargas, 558 F.2d at 633. The court in Gonzalez Vargas was unhappy “because the *116trial was otherwise a good trial.” Ibid. That cannot be said of the trial of the instant case, which was a ragged one. Nonetheless, we reverse with some reluctance because the evidence of guilt accumulated by the Commonwealth was so strong and so much trial time (thirty days) has already been spent. “ [P]rosecutorial misconduct unnecessarily risks reversal of a conviction that otherwise might have been affirmed — all at great cost to the Commonwealth as well as to the defendants.” Commonwealth v. Smith, 387 Mass. 900, 904 (1983).

Nor was this the only incident of the kind. Earlier, when Mr. Shulman, counsel for Gagnon, was cross-examining another prosecution witness, Micheline Roy, he began a question with the words, “is it true.” The district attorney, in objecting to the question said, “Excuse me, I’m going to object, if your Honor please, to the prefacing of any question, ‘is it true.’ I would assume that everything she is saying is true.” The judge observed, “Yes, my thought, too.” Defense counsel did not object and rephrased the question.

During closing argument the district attorney stepped very close to, if indeed not over, the line several times by stating his views. On one occasion, he remarked, “Eddie Petrick isn’t a liar. Eddie Petrick told you exactly what he saw.” He said of two other witnesses respectively: “a very honest witness on the stand, who wants to help and tell you the truth” and “a very, very, very honest witness.”

As to the witness Margaret Nelson, the district attorney told the jury in closing argument about things she had told him in an interview but which, he explained to the jury, could not be introduced because they were hearsay. This accomplished a double fault: it discussed testimony not in evidence and suggested the Commonwealth had more evidence in its quiver which would have been used, but for technical obstacles. See Commonwealth v. Ryan, 8 Mass. App. Ct. 941 (1979). It is an inadequate justification for referring to Nelson’s extra-judicial statements that some of the subjects they touched on had been referred to in a deposition of Nelson which one of the defendants put in evidence.

*117To none of these later remarks did the defendants object. Accordingly, claims of appeal based on them are lost, Commonwealth v. Underwood, 358 Mass. 506, 509 (1970), unless we consider them in order to avoid a substantial risk of a miscarriage of justice. Commonwealth v. Freeman, 352 Mass. 556, 563-564 (1967). Commonwealth v. Daigle, 379 Mass. 541, 549 (1980). As such incidents multiply during the course of a trial, the specter of a miscarriage of justice becomes more difficult to exorcise. Since, however, for the reasons stated in this opinion, it will be necessary to try this case again, we shall content ourselves with an admonition that the prosecutor, on retrial, would be well advised to adhere to the requirements of Commonwealth v. Earltop, 372 Mass. 199, 204-207 (1977) (Hennessey, C.J., concurring), Commonwealth v. Shelley, 374 Mass. 466, 470-472 (1978), Commonwealth v. Smith, 387 Mass. at 903, Commonwealth v. Villalobos, 7 Mass. App. Ct. 905 (1979), and Commonwealth v. Hogan, 12 Mass. App. Ct. 646, 651-652 (1981), to mention a sample of authorities. Compare Commonwealth v. Mahdi, 388 Mass. 679, 690-699 (1983).

2. Validity of peremptory challenges of jurors. Trial of this case began on May 1, 1978, and jury selection, which consumed nine court days, ended on May 12, 1978.7 The defendants complain that the prosecution exercised its peremptory challenges to exclude persons with French surnames from the jury “solely on the basis of bias presumed to derive from [their] membership in [that] group.” Commonwealth v. Soares, 377 Mass. 461, 488, cert. denied, 444 U.S. 881 (1979). Soares had not been decided when the case before us was tried, but the rule adopted in Soares applies to defendants in all cases pending on direct appeal on the date of the Soares decision “where the record is adequate to raise the issue.” Commonwealth v. Soares, 377 Mass. at *118493 n.38. The instant case was on direct appeal (notices of appeal having been filed June 19, 20, and 26, 1978) when Soares was decided and is distinguishable from Reddick v. Commonwealth, 381 Mass. 398, 399-404 (1980), in which the court held that the Soares principle should not, in all but a narrow category of cases (not here relevant), be applied retroactively in cases where direct appeal rights have been exhausted — or have expired — and there is a postcon-viction or collateral attack.

There were twenty-three persons with names that were arguably French8 called from the venire, and the prosecution challenged nineteen of them. The defense challenged the other four. The jury selected, consequently, contained no persons with apparent French names.

Assuming, for the moment, an intent by the prosecution to exclude those of French-Canadian origin from the jury, none of the defendants complained about it at trial. This was hardly to be wondered at since attacks on peremptory challenges designed to keep distinct groups off a jury had prior to Soares been peremptorily rejected. See, e.g., Commonwealth v. Mitchell, 367 Mass. 419, 420 (1975); Commonwealth v. Cranshaw, 4 Mass. App. Ct. 630 (1976). See also Swain v. Alabama, 380 U.S. 202, 220-224 (1965). The question arises, nevertheless, whether “the record is adequate to raise the issue” without express objection or calling of attention to the peremptory challenges complained of. We read Soares and Reddick as permitting the question to be raised in a case on direct appeal when Soares was decided if the facts on which the question is to be decided can be gleaned from the transcript. See Reddick v. Com*119monwealth. 381 Mass. at 403; Commonwealth v. Robinson, 382 Mass. 189, 195 n.4 (1981); Commonwealth v. Mahdi, 388 Mass. at 689-690. Indeed, it would be captious and cynical to say that the door was open on direct appeal cases and then to slam the door shut because lawyers failed to object to practices which were approved under the governing State and Federal cases. The issue, involving subsequent developments in constitutional law, is one as to which courts do not require defense counsel to be clairvoyant. Commonwealth v. Kater, 388 Mass. 519, 533 (1983). Compare Commonwealth v. Walker, 379 Mass. 297, 300 (1979), in which no exceptions were taken at trial, but the defendant noted for the record the prosecution’s challenges of black persons and raised the issue on a motion for a new trial. The transcript here is adequate in terms of disclosing: (1) the number of challenges; (2) the manner of challenge; (3) the names of persons seated; and, (4) the percentage of various groups challenged, to enable us to consider whether the peremptory challenges were designed to exclude a discrete group.

It may fairly be asked whether, in a society as heterogeneous as ours, it is wise to fragment the population excessively into subgroups. To do so runs counter to cherished and valid notions of America as a melting pot. Moreover, names are anglicized, women adopt married names, and names becomes less than a totally reliable badge of ethnic identity. A member of the venire with the less than Gallic name of Wanda J. Clark, for example, said her grandfather was of French-Canadian descent. (She was challenged by the prosecution.) In the Northeast, however, French-Canadians have been recognized as a group with distinct cultural and linguistic traditions, and it is perhaps enough, for purposes of this case, to recognize that the prosecutor regarded French-Canadian identity as a significant factor in jury selection. He expressed his view that where the jurors were born was very important. He attributed significance to a maple leaf pin which a prospective juror was wearing *120and later challenged him.9 Among the “generic group affiliations which may not permissibly form the basis for juror exclusion” is national origin. Commonwealth v. Soares, 377 Mass. at 488-489 & n.33. Cf. Commonwealth v. Festa, 369 Mass. 419, 430 (1976).

The percentage of persons with French surnames who were challenged was high: eighty-three percent (compared to ninety-two percent of eligible black jurors in Soares). Thirty-six percent of jurors who did not have French names were challenged. The number of persons of apparent French ethnicity who were challenged by the prosecution, nineteen, was relatively high. This was not a case where only one member of the group was challenged. See Commonwealth v. Clark, 378 Mass. 392, 407-408 n.17 (1979). As the number of members of a particular group who are challenged grows larger, the presumption of proper use of the peremptory challenge grows weaker. Cf. Commonwealth v. Walker, 379 Mass. at 301. That the prosecution was prepared to let four persons with French surnames sit as jurors, on the other hand, supports the presumption of propriety. See Commonwealth v. Kelly, 10 Mass. App. Ct. 847 (1980) (three blacks seated, two excluded). On balance, however, the challenge of nineteen members of a particular class, a number higher than in Soares and in the cases noted in the margin dealing with the Soares issue,10 on the facts *121in this case, 11 shows a pattern designed to exclude a discrete group from the jury. Commonwealth v. Soares, 377 Mass. at 490.

We have considered whether the prosecution could properly have apprehended that potential jurors of French-Canadian background might know French and would follow the original testimony of French-speaking witnesses (including the defendants) rather than translation of the testimony into English. Of the twenty-three potential jurors with French-Canadian surnames whom we have considered, ten admitted to understanding French, although some said their French was rusty. All twenty-three had passed a preliminary screening by the judge in which he allowed to remain in the jury pool only those jurors who had agreed to be bound by the translation into English. As is generally the case with instructions to jurors, we proceed on the premise that the jury will abide by them. Commonwealth v. Gordon, 356 Mass. 598, 604 (1970). But see Commonwealth v. DiMarzo, 364 Mass. 669, 681 (1974) (Hennessey, J., concurring). Neither party, as the court observed in Commonwealth v. Festa, 369 Mass, at 430, has the right to have a juror excused solely because that juror may understand the language of the witness.

Accordingly, the jury selection process was defective under art. 12 of the Massachusetts Declaration of Rights, and this would entitle the defendants to a new trial. Commonwealth v. Soares, 377 Mass. at 486.

*1223. Evidence seized in warrantless search. Roughly one month before the trial began, there was a hearing, which consumed ten days, on motions to suppress inculpatory evidence seized by Canadian police and made available to the police in Springfield. The judge denied the motions but made no findings of fact to support his ruling, a circumstance which handicaps our review. See Commonwealth v. Garcia, 379 Mass. 422, 428 (1980) (“We emphasize once again the importance of findings of subsidiary facts in such a situation”).

It will be recalled that there was a search of Gagnon’s apartment in Quebec. This yielded, among other things: firearms, knitted caps with eye slits, newspaper clippings about the Springfield bank robbery, telephone numbers, photographs, swimming trunks (matching those in which a suspect in the holdup had been seen), wall posters, a street map of Springfield, currency, and a bullet proof vest, all of which had probative force in building the Commonwealth’s case. That search had been conducted without a warrant, and Gagnon invokes the protection of the Fourth Amendment to the United States Constitution. Searches in foreign countries by the police of foreign countries do not, however, have to comply with American requirements, and the exclusionary rule developed under the Fourth Amendment, as a general proposition, has no application. This is because the object of the exclusionary rule is to deter the police from illegal searches and seizures, a purpose not susceptible of achievement so far as the police of another nation are concerned; they are not likely to be instructed or deterred by the suppression of evidence in accordance with rules by which they are not accustomed to play. Commonwealth v. Wallace, 356 Mass. 92, 95 (1969), and cases cited. United States v. Rose, 570 F.2d 1358, 1361-1362 (9th Cir. 1978).

To this general rule two exceptions have developed. The first calls for invocation of the exclusionary rule if the circumstances attending the search and seizure are such that they shock the judicial conscience. Birdsell v. United States, 346 F.2d 775, 782 n.10 (5th Cir.), cert. denied, 382 *123U.S. 963 (1965). United States v. Rose, supra at 1362. Stowe v. Devoy, 588 F.2d 336, 341-342 (2d Cir. 1978), cert, denied, 442 U.S. 931 (1979). There was nothing about the search of Gagnon’s locker and apartment that shocks the conscience. It was not a random search, but one based on information. No violence, torture, or deviousness was involved. See, e.g., United States v. Toscanino, 500 F.2d 267, 276 (2d Cir. 1974).

The second and more pertinent exception is that the exclusionary rule may be invoked if American police participate in the search in the foreign country, or if the authorities in the foreign country who conduct the search, in fact, are acting under the direction of their American counterparts, and as their agents. More than cooperation by American police must appear; there must be direct participation or, as it is sometimes said, a joint venture by the American and foreign police. So, for example, the use by Mexican officials of a deputy sheriff from Texas as an interpreter in Mexico in questioning a defendant was insufficient evidence of collaboration. Birdsell v. United States, 346 F.2d at 782. Cooperation by United States agents with Philippine authorities before and after a raid did not establish a joint venture because there was no evidence that the American police either instigated, or were physically present during, the raid. Stonehill v. United States, 405 F.2d 738, 746 (9th Cir. 1968), cert. denied, 395 U.S. 960 (1969). A telephone call to Toronto police by Federal agents in New York concerning an American living in Toronto who might have information about stolen securities did not make the agents participants in the search that followed. United States v. Morrow, 537 F.2d 120, 140 (5th Cir. 1976), cert, denied sub nom. Brennan v. United States, 430 U.S. 956 (1977). In United States v. Benedict, 647 F.2d 928, 930-931 (9th Cir.), cert. denied, 454 U.S. 1087 (1981), presence by American agents at a search of an apartment, which the Thai police had initiated, did not indicate more than a passive role by the Americans. See also United States v. Rose, 570 F.2d at 1362; United States v. Maher, 645 F.2d *124780, 783 (9th Cir. 1981). Compare United States v. Hensel, 509 F. Supp. 1364, 1372-1373 (D. Me. 1981) (cooperation between Coast Guard and Canadian officials in high seas chase, boarding and search of a vessel sufficient to make out a joint venture). See Restatement (Revised) of the Foreign Relations Law of the United States § 443(4) & comment a (Tent. Draft No. 3, 1982).

Corporal Dube, the Canadian officer who had directed the search of Gagnon’s locker and apartment on February 4, 1978, testified at the suppression hearing that he had been induced to do so by a tip from an informant, received around 1:00 p.m., that guns were stashed in the locker and were to be used in an assassination that very evening. Defense counsel, who were attempting to find enough linkage between Massachusetts and Canadian police to establish that the search had been a joint venture, probed for the identity of the informer in order to test if there was one and, if he existed, whether he was from Massachusetts or Canada or linked to the Springfield case. In this effort they were promptly cut off by the judge.

The State usually has a privilege to withhold the identity of an informer, particularly where the issue is suppression of illegally obtained evidence.12 Commonwealth v. Ennis, 1 Mass. App. Ct. 499, 501 (1973), and cases cited. Commonwealth v. Collins, 11 Mass. App. Ct. 126, 139-140 (1981). Commonwealth v. Abdelnour, 11 Mass. App. Ct. 531, 534-537 (1981). See Commonwealth v. Douzanis, 384 Mass. 434, 441-443 (1981). If the credibility of the informer is sharply drawn in question, the trial judge may conduct an examination in camera to see if the information obtained is reliable or credible. Commonwealth v. Abdelnour, 11 Mass. App. Ct. at 536 n.5 (which collects authorities). See Proposed Mass.R.Evid. 509(c)(3) (July, 1980).

*125Here, Dube, in response to specific questions of counsel, had testified unambiguously that the informant was a Canadian policeman, and not an American. Questions by defense counsel as to whether the informant was an undercover agent were excluded. It would have been better if the judge had allowed those questions to be asked since the overt or covert status of the informant has a bearing on whether his identity may be disclosed without drying up the flow of information to which the police have access. Cf. Roviaro v. United States, 353 U.S. 53, 62 (1957). But the judge heard enough so that he could perform his role of deciding whether he needed disclosure of the informant to gouge Dube’s credibility. McCray v. Illinois, 386 U.S. 300, 308-309 (1967). State v. Burnett, 42 N.J. 377, 388 (1964).

Defense counsel did not manage more than an assertion of doubt about the existence of an informant. In the face of Dube’s description of the informant’s nationality and occupation, the occasion called particularly for “an adequate threshold demonstration . . . that the police [had] fabricated the informant’s existence.” Commonwealth v. Abdelnour, 11 Mass. App. Ct. at 535-536. See also Commonwealth v. Douzanis, 384 Mass. 434, 442-443 (1981). None of the Canadian police behavior in making the search was inexplicable in light of Dube’s testimony. See 1 LaFave, Search and Seizure § 3.3, at 578-579 (1978); Commonwealth v. Ahdelnour, supra at 537. Indeed, it is hard to know why Dube needed to invent the “assassination plot” story if either Canadian or American colleagues had asked him to search Gagnon’s premises in connection with the Springfield holdup.

Even if, as the defense urged at side bar, the identity of the informant might have established a link between Dube and the Springfield police, that, without more, showed little promise of establishing the very close collaboration which, under the cases previously discussed, would cause the Fourth Amendment to apply to a foreign search. Nothing could have been lost by an in camera examination of *126Dube by the judge, but we do not think the judge’s refusal to do so was an abuse of his considerable discretion.

4. Failure to allow inspection of Dube’s report. At an earlier stage of the proceedings, Gagnon had moved to be allowed to inspect written statements made by prosecution witnesses. A Superior Court judge (who was not the same judge as the one who presided at the suppression hearing and at the trial) allowed the motion on the authority of Commonwealth v. Lewinski, 367 Mass. 889, 902-903 (1975). That opinion provides that a defendant might, without showing of a particularized need, move for discovery of prior written statements of prosecution witnesses which are available to the prosecution and are related to the subject matter of their testimony at trial. Id. at 902. Allowance of the motion is not automatic, ibid., but here the motion was granted. It developed in examination of Dube that he had made a written report concerning his conversation with his informant and about the search of Gagnon’s apartment. That report was physically available in Springfield. Defense counsel pressed their right to examine the report under the previously allowed motion and under Lewinski. Without inquiring whether the report was previously known to the prosecution, or inquiring in camera — as requested by the defense — whether the report disclosed security reasons (e.g., revealing confidential investigatory material, notably the identity of the informer) for not allowing inspection of it (see Lewinski, supra at 902), the judge flatly refused any inspection of the report.

To have refused an in camera examination of Dube’s written report to see if it cast doubt on his oral testimony (he was not an insignificant witness) was error, and the judge compounded it by failing to identify and preserve the report as part of the record on appeal. Commonwealth v. Lewinski, 367 Mass. at 903. Commonwealth v. Campbell, 378 Mass. 680, 700-702 (1979). See generally Commonwealth v. Baldwin, 385 Mass. 165, 173-178 (1982). In Campbell, supra, the court, in the absence of the report in the record, remitted the defendants to motions for a new trial. The *127judge who presided at the suppression hearings and at the trial in this case has retired, and it is more appropriate that the question whether Dube’s report may be inspected be considered at the new trial, which is required in any event. See Mass.R.Crim.P. 14(a)(2) & 23(a)(1), 378 Mass. 874, 893 (1979).

5. Identification of two defendants in photographs. At the Shawmut First Bank there was a device which kept a running photographic record of everyone who came into the main business floor. Guy Dessureault, a detective of the Three Rivers (Canada) police department, examined pictures made on June 3, 1977, and in a sequence of some fifteen pictures identified Bourgeois and Gagnon as present in the bank. Photographs which showed the presence together of two men from different cities in Canada in a bank in Springfield one week before the holdup13 had obvious probative value. The defense objected that Dessureault ought not to be allowed to testify that among the faces in the pictures were those of Bourgeois and Gagnon, i.e., the jury were as able as a police officer to match the defendants with the faces in the photographs. See Commonwealth v. Nassar, 351 Mass. 37, 41-42 (1966).

Between the time, however, when the pictures were taken in June, 1977, and the trial in 1978, the defendants had grown beards and altered their hair styles. Dessureault had arrested Bourgeois and Gagnon and was familiar with their earlier guises.14 On these facts the opinion of Dessure-ault was of value because the subject matter to which the testimony relates, i.e., the match-up between two of the defendants and faces in the pictures, could not be reproduced or described to the jury precisely as it appeared to Dessure-ault, who was familiar with the defendants’ earlier appearance. Also the facts were such as persons in general are *128capable of comprehending and understanding. Commonwealth v. Vitello, 376 Mass. 426, 459-460 (1978). No error, therefore, attended Dessureault’s matching of the photographs with the defendants, save for one of those photographs.15

6. The circled photograph. One of the bank photographs had two heads circled in red and with red numbers next to them. On the back the numbers were keyed to Bourgeois and Gagnon. The initials GD appeared. Dessureault was allowed to testify that the markings were his as were the initials. He further testified that he had received the picture from the Springfield police with an inquiry whether he recognized any of the faces in the picture. The inked and initialed identification of Gagnon and Bourgeois had been his response.

Admission of the marked up photograph and Dessureault’s testimony was sharply objected to as proving nothing other than that Bourgeois and Gagnon were known to the Canadian police and, inferably, were bad men. See Commonwealth v. Clifford, 374 Mass. 293, 298 (1978), and cases cited; Commonwealth v. Cefalo, 381 Mass. 319, 336 (1980). As more than a dozen photographs had been admitted from the bank sequence of June 3, 1977, for purposes of placing the defendants in the bank, the photograph in that sequence marked by Dessureault and his accompanying testimony had little, if any, additional probative value, and that was overwhelmed by prejudicial effect. Commonwealth v. Richmond, 371 Mass. 563, 565-566 (1976). Indeed, it is hard to see what purpose the marked picture and Dessureault’s explanations of the markings could have had other than to brand Bourgeois and Gagnon as “pros,” the characterization which the district attorney applied to them in *129closing argument. Compare Commonwealth v. Chalifoux, 362 Mass. 811, 817 (1973). Of course, if relevant, evidence is not made inadmissible because it has a tendency to indicate that the defendant might have run afoul of the criminal justice system before. Commonwealth v. Des-champa, 1 Mass. App. Ct. 1, 3 (1972). The failing here is that there was no other point to admitting the marked picture in view of the substantially similar unmarked pictures which were introduced in evidence. Admission of the marked photograph was error. Compare Commonwealth v. Westmoreland, 388 Mass. 269, 279 (1983).

7. Admission of Gagne’s prior convictions. Norman Gagne, one of the three defendants, took the stand. On direct examination his counsel, Mr. Gordon, brought out that Gagne had served time in Canadian jails. The prosecution was equipped with records of Gagne’s conviction of conspiracy to commit armed robbery; illegal possession of a carbine; illegal possession of a revolver; and illegal possession of a motor vehicle.16 After extensive colloquy among counsel and the judge, Gagne was examined by the prosecutor, without objection, about those convictions, and certified records of them were, by prior agreement between counsel, admitted in evidence. Gagne claims on appeal that his lawyer’s agreement to the admission of the convictions in evidence constituted ineffective assistance of counsel for the reason that the Commonwealth had not shown that Gagne either had the benefit of counsel or had waived counsel when the convictions were obtained.

Evidence of conviction of a crime is, of course, admissible for the limited purpose of impeaching the credibility of a witness, subject to certain express limitations. G. L. c. 233, § 21. See the discussion in Liacos, Massachusetts Evidence 150-158 (5th ed. 1981). See also Proposed Mass.R.Evid. 609 (July, 1980). But the defendant must have been represented by counsel, or have knowingly and voluntarily waived *130counsel at the time of the conviction. Loper v. Beto, 405 U.S. 473, 483 (1972). Commonwealth v. Cook, 371 Mass. 832, 833 (1977). The burden of showing that counsel was present or waived is on the prosecution. Commonwealth v. Barrett, 1 Mass. App. Ct. 332, 335-336 (1973), and cases cited.

We will not speculate whether defense counsel for Gagne17 knew that Gagne had counsel at the time of the convictions, or whether counsel was uncertain what information the prosecution had. We are certainly not prepared to say that his tactical decision constituted ineffective assistance of counsel. This trial lasted six weeks and was exceptionally hard fought. Pretrial motions were made and extensively argued; 245 exceptions were taken by the defense.18 It is hardly fair, in the relative calm of the appellate process, to cry ineffective assistance of counsel.

Because the question may arise again on retrial, it is necessary to discuss whether a conviction in a foreign country must have been counseled or counsel-waived. In Canada a person who has been arrested or detained has a right to call and speak with a lawyer. See Canadian Bill of Rights § 2, as appearing in Martin’s Annual Criminal Code 837 (1981); Cohen, Due Process of Law — The Canadian System of Criminal Justice 17-21, 77-79 (1977). It appears Canadian law does not require that a defendant have a lawyer or that he be tried with the assistance of a lawyer. Spetz, Canadian Criminal Law 163 (1972). See State v. Meyer, 26 Wash. App. 119, 127 n.3 (1980). If Canada does not require the presence of counsel to the same extent our jurisprudence does,19 may not an uncounseled conviction be used on the *131basis of the same reasoning as permits the introduction of evidence illegally seized, namely, that rules devised to govern our criminal justice procedures have no application to the criminal justice system of another country? A difference between the two is that the exclusionary rule as to illegally obtained evidence — even though the evidence is reliable — is designed to encourage lawful police practices, and to deter unlawful ones, while the concern about un-counseled convictions is based on their possible unreliability. The elements of a fair system of justice, however, are far from absolute, and there is a certain arrogance in labeling as unfair and deficient a system which does not comport with the notions of judges and Legislatures in this country. See Carey v. Zayre of Beverly, Inc., 367 Mass. 125, 128-130 (1975), in which evidence of an uncounseled conviction was admitted in a civil action, in part on the ground that no deterrent purpose could be served by excluding it, since the authorities would have little interest in the outcome. The same may be said of court authorities of a foreign country; they are not likely to be greatly concerned about the effect of their procedures on other jurisdictions. See also State v. Meyer, 26 Wash. App. at 125-128, in which the court said that comity required giving effect to foreign convictions, except in an extraordinary case. Compare People v. Wallach, 110 Mich. App. 37, 69-72 (1981), which places on the prosecutor the burden of establishing whether a foreign conviction was obtained in accordance with fair procedures.

An extraordinary case would be one where the foreign proceedings were blazingly unfair, e.g., involving torture, shocking psychological pressure, or a refusal to permit a defendant to testify on his behalf or to confront his accusers. Although the burden is on the prosecution in cases involving convictions by a jurisdiction in (or operating under the laws of) the United States to establish that a conviction was counseled (or that counsel was waived), Commonwealth v. Barrett, 1 Mass. App. Ct. at 335-336, the burden does not fall on the prosecution to demonstrate that the foreign con*132viction was fairly obtained. That would require endless screening of foreign records, often with attendant language problems. If there was something extraordinary about the foreign proceeding, the facts are more readily available to the defendant. Federal courts which have considered the issue have placed on the defendant the burden of demonstrating lack of due process in a foreign conviction. United States v. Wilson, 556 F.2d 1177, 1178 (4th Cir.), cert. denied, 434 U.S. 986 (1977). United States v. Manafzadeh, 592 F.2d 81, 90 (2d Cir. 1979). United States v. Rodarte, 596 F.2d 141, 146 (5th Cir. 1979).

The balance of the issues on appeal are unlikely to recur at a new trial. Those concerned: an outburst by the defendant Bourgeois;20 a restriction on the closing argument of counsel for Bourgeois; and a claimed error in the instruction on joint enterprise that, in context, is more likely a typographical error in the transcript.

The judgments are reversed, the verdicts are set aside, and the case shall stand for a new trial.

So ordered.