Ronald W. Jordan appeals his conviction of assault with intent to murder by a jury in the District Court for the Eastern District of Virginia. He assigns as error, inter alia, the failure of the court to grant a continuance to enable investigation of witnesses, the failure of the court to order the production of a government witness’ grand jury testimony, and the disallowance of a motion *101to suppress the victim’s in-court identification of the defendant. We think none of these assignments of error (nor numerous others we need not discuss) requires reversal, and accordingly affirm the judgment below.
I.
Jordan was indicted for an apparently unprovoked knife attack on another inmate, Eugene H. Cohen, at Lorton Reformatory in Virginia. In planning his defense, his court-appointed attorney met informally with the United States Attorney and was told the substance of the testimony which two eyewitnesses to the attack, Watkins and Williams, would give. However, the government refused to disclose the names of these two witnesses, and a motion to compel disclosure under Rule 16, Federal Rules of Criminal Procedure, was denied. On the day of the trial, the defendant moved for a continuance when the identity of the eyewitnesses became known, but this, too, was denied. Jordan claims that to deny both discovery of these witnesses’ names and a continuance to investigate them once their identity is known was error. We disagree.
It is settled in this circuit that “[ojnly in a capital case is the government required to furnish a pretrial list of government witnesses.” United States v. Chase, 372 F.2d 453, 466 (4th Cir. 1967); 18 U.S.C. § 3432. The court in its discretion may order the government to produce such a list under Rule 16, Federal Rules of Criminal Procedure,1 but whether or not it is an abuse of discretion not to do so, and whether it is an abuse of discretion not to grant a continuance once the witnesses’ names become known, depends, we think, on whether the denial of such motions amounts to a denial of the defendant’s right of confrontation in violation of the Sixth Amendment. We find no such violation here.
Of course, the clearest violation of the Sixth Amendment’s guarantee of the right of confrontation is where the defense is not allowed to examine the prosecution witnesses at all. Brookhart v. Janis, 384 U.S. 1, 86 S.Ct. 1245, 16 L.E.2d 314 (1966). The Supreme Court has recognized, however, that a defendant’s Sixth Amendment rights may also be violated by less than a complete denial of all cross-examination. Alford v. United States, 282 U.S. 687, 51 S.Ct. 218, 75 L.Ed. 624 (1931); Smith v. Illinois, 390 U.S. 129, 88 S.Ct. 748, 19 L.Ed.2d 956 (1968). We think Jordan fails to show a sufficient diminution of the right of cross-examination to come within the protection of the rule of these cases.
In Alford the district court refused to allow the defense to question a prosecution witness about his present residence. In reversing, the Supreme Court held the defendant was entitled to elicit on cross-examination that the witness was in federal custody on the theory that a jury might infer “that his testimony was biased because given under promise or expectation of immunity, or under the coercive effect of his detention by officers of the United States, which was conducting the present prosecution.” (citations omitted). Alford v. United States, supra 282 U.S. 687 at 693, 51 S. Ct. 218 at 220. Thus the trial court’s error consisted of cutting off “all inquiry on a subject with respect to which the defense was entitled to a reasonable cross examination.” Alford, supra at 694, 51 S.Ct. at 220.
In Smith v. Illinois, supra, the issue upon which the outcome of the trial turned was the credibility of the chief prosecution witness, whose testimony differed in crucial respects from that of the defendant charged with selling narcotics to this witness. In light of the importance of the credibility resolution, the Court held that to deny to the defense the right to ask this witness his *102correct name and address, when the witness admitted that the name he had given on direct examination was false, was error. “To forbid this most rudimentary inquiry at the threshold is effectively to emasculate the right of cross-examination itself.” Smith, supra, 390 U.S. 129 at 131, 88 S.Ct. 748 at 750.
We think neither of these cases helps Jordan. Unlike Smith and Alford, the scope of cross-examination was not in any way curtailed. Furthermore, from his conversations with the United States Attorney, Jordan’s attorney was aware of what the two eyewitnesses would say on direct examination. He was also aware that they were both convicted felons, and this fact was brought out on cross-examination. Likewise, he knew the name of the victim and that the victim would positively identify Jordan as his assailant.
Thus, the defendant’s complaint boils down to the theory that, if the defense had known the names of the witnesses, or, once having ascertained their names, if a continuance had been granted, it might have been possible to unearth something more with which to discredit their testimony. We recognize that counsel may sometimes need time to investigate witnesses. But on the facts of this case it was not an abuse of discretion to fail to grant a continuance.
Even now, long after the event, it is not suggested to us that investigation would have been fruitful. These witnesses were not presented under false colors as persons of apparently good character and reputation, but, instead, the fact that they were convicted felons was brought out at the trial. Any further testimony as to the specific nature of their offense or offenses would have been cumulative. That they were felons, without more, tends to impeach credibility. Moreover, counsel was not refused the opportunity to inquire about any and all prior offenses.
Although we do not base our decision on the harmless error doctrine, it is worth mentioning that, unlike Smith, supra, the victim’s testimony positively identifying Jordan as his assailant was itself enough to sustain conviction even if Williams’ and Watkins’ testimony had somehow been even more discredited than it was. Furthermore, Jordan’s alibi that he was playing basketball at the time of the knife attack was flatly contradicted by the testimony of prison guards.
We think the government properly refused to disclose the names of these inmate witnesses to the assault. To have done so might have endangered them. We hold that it was not error for the trial judge to decline to grant a continuance for the purpose of further investigation of these witnesses prior to cross-examination.
II.
The United States has admitted that it was error to fail to supply the defense with a transcript of Watkins’ grand jury testimony.2 Where such material has been erroneously withheld from the defense, we think the trial court is usually in the best position to determine if the defendant could have used the grand jury testimony in his defense. Harris v. United States, 140 U. S.App.D.C. 21, 433 F.2d 1127 (1970). However, since Watkins’ testimony before the grand jury does not vary from his testimony at trial, remand would serve no purpose. The error is harmless beyond a reasonable doubt.
III.
Jordan’s contention that his victim’s in-court identification should have been suppressed because tainted by an *103impermissibly suggestive out-of-court identification is without merit. Not only did the evidence indicate that Cohen’s in-court identification was not influenced by the out-of-court photo identification, but also we do not think that the fact that the defendant’s photograph had the words “Dist. of Col. Dept, of Corr.” in very small letters beneath his picture is suggestive in this case. Obviously Cohen’s assailant was in custody and all of the photographs shown to Cohen were mug shots, each bearing the name of a prison. Cohen had no way of knowing when these pictures were taken or in which prison, if any, the people represented by the photographs were when he examined them. Thus a geographical indication on the pictures would not help him identify his assailant.
We have examined the defendant’s other contentions and find them without merit. The judgment of the district court is
Affirmed.
. United States v. Jepson, 53 F.R.D. 289 (E.D.Wis.1971); United States v. Leichtfuss, 331 F.Supp. 723, 732 (N.D.Ill. 1971). See Will v. United States, 389 U.S. 90, 88 S.Ct. 269, 19 L.Ed.2d 305 (1967).
. Thus we do not reach the question of the extent to which Dennis v. United States, 384 U.S. 855, 86 S.Ct. 1840, 16 L.Ed.2d 973 (1966), has changed the circumstances, if any, under which grand jury minutes may be withheld from the defense. See Harris v. United States, 140 U.S.App.D.C. 21, 433 F.2d 1127 (1970); United States v. Youngblood, 379 F.2d 365 (2d Cir. 1967).