We are asked to review the District Court’s denial of a new trial sought by Appellant on the ground of newly discovered evidence. Because of other factors in the case which first came to our notice during oral argument and were not presented to the District Court, we conclude that we must remand for further hearings.
Appellant’s “newly discovered” evidence presented in the hearing on his new trial motion was that certain alibi witnesses, if called, would have placed him far from the scene of the crime at the critical hour. The District Court heard these witnesses and concluded that, although they would indeed so testify, they had been known and available to Appellant at the time of trial and that there had been a lack of diligence on Appellant’s part. We see no reason to disturb the District Court’s finding on that score.
However, at oral argument in this court Appellant’s counsel stated that the failure to call the alibi witnesses at the time of the trial was attributable to Appellant’s original trial counsel,1 who had been aware of these alibi witnesses but had consciously failed to call them. Although he suggested that the original trial counsel might not have had a good reason for this failure, Appellant’s counsel in this court explained his own failure to call original counsel as a witness at the hearing on the motion for new trial by saying that he had not wanted to embarrass trial counsel and expose him to a suggestion of ineffective assistance. High standards of professional courtesy *136and etiquette between members of the bar are important elements of an efficient system of justice, but if'duty to the client and deference to a professional colleague come into conflict, plainly the latter must yield to the former.
On the record before us we cannot make an appraisal of whether trial counsel’s action in failing to call the alleged alibi witnesses was a tactical decision based, for example, on a judgment that their credibility might be impeached successfully, or whether there was a failure on the part of trial counsel to explore the matter fully. We make no assumptions on the answer to this question. If the former is the case, we would not disturb the action of the District Court; but if there was in fact a failure to make inquiry as to these witnesses, Appellant’s counsel on the motion for a new trial had a clear duty to bring that fact to the attention of the Court. That this would require calling trial counsel as a witness, and perhaps open him to the possibility of embarrassment is beside the point. Apart from the impact on Appellant’s possible right to a new trial, once the suggestion of ineffectiveness is raised. Appellant’s original trial counsel is entitled to an opportunity to meet the implied charge.
We recognize that the inquiry on remand may well prove fruitless as far as Appellant is concerned. The purpose of the remand is to bring out relevant facts not previously presented to the District Judge, so that he can make a fully informed decision. Although at the time of the hearing on Appellant’s motion for a new trial no one claimed that trial counsel had been ineffective, Appellant’s counsel in this Court has now, inadvertently or otherwise, raised questions on this score, which must be answered.
We therefore remand the record to the District Court so that it may be supplemented by the testimony of trial counsel and by the District Court’s findings on this aspect of the case to the end that the District Court may take any action it thinks proper in light of this testimony. We retain jurisdiction subject only to the power of the District Court to grant a new trial if it concludes that is the correct course.
Remanded for further proceedings consistent with this opinion.
. See Thompson v. United States, 88 U.S.App.D.C. 235, 188 F.2d 652 (1951).