This appeal arises from a jury conviction of assault with intent to commit robbery while armed (D.C.Code 1973, §§ 22-501, -3202) and assault with a dangerous weapon (D.C.Code 1973, § 22-502).1 Appellant contends that the trial judge erred in (1) denying appellant’s motion to dismiss for lack of speedy trial, (2) failing to give a cautionary instruction sua sponte when evidence of prior inconsistent statements was admitted to impeach a defense witness, (3) giving certain instructions on alibi to the jury, and (4) refusing to order a new trial. We affirm.
On the evening of November 3, 1973, Clarence L. Johnson, Jr. and three companions were walking toward Fast Eddie’s Carryout when they were approached by a man carrying a sawed-off shotgun. The assailant demanded that Mr. Johnson give him “the bam.”2 When Mr. Johnson responded that he did not have any “bam,” the assailant forced Mr. Johnson at gunpoint into a nearby church doorway, took ten dollars from him and shot him in the side of his mouth. Mr. Johnson made his way into the carryout where he waited for the ambulance which transported him to the hospital.
While in the hospital, Johnson was shown a stack of photographs (which included appellant’s picture) by Detective Miller but failed to identify appellant’s picture. Detective Miller returned a short time later and showed Mr. Johnson the sanie group of photographs. This time Mr. Johnson identified appellant. At trial he testified that he had not identified appellant the first time the pictures were shown to him because he wanted to avenge the assault himself, but after reflection he had decided to let the police handle the matter.
At trial, Mr. Johnson again identified appellant as his assailant. Johnson’s brother, Walter, who had been with him on the night in question gave a general description of the assailant consistent with appellant’s appearance. Detective Miller testified that before he showed the photographs to Johnson a second time he assured Johnson that if he was afraid to identify anyone, the police would protect him.
The defense presented seven witnesses. Three persons testified that they were in the vicinity of Fast Eddie’s on the night in question, that they knew appellant and that appellant was not the assailant. Three persons testified that they were with the appellant that evening and that he was in a different part of town at the time of the shooting. The jury reached a partial verdict and the court granted a mistrial on several other counts upon which the jury could not decide.
After the trial, defense counsel renewed an earlier motion to dismiss the indictment for lack of speedy trial and also moved for a judgment of acquittal or, in the alternative, for a new trial. After extensive hearings, the trial court denied both motions.
I. Speedy Trial
Appellant contends first that the more than fourteen months delay between *456his arrest and the commencement of the trial denied him his Sixth Amendment right to a speedy trial. While this court has held that a delay of a year or more gives prima facie merit to a claim of denial of speedy trial, Branch v. United States, D.C.App., 372 A.2d 998 (1977), the length of delay is not the only material factor.3 In Barker v. Wingo, 407 U.S. 514, 92 S.Ct. 2182, 33 L.Ed.2d 101 (1972), the Supreme Court identified three other elements which must be examined in weighing a speedy trial claim: (1) the reasons for the delay, (2) the defendant’s assertion of his right, and (3) prejudice to the defendant. In discussing these factors the Court stated:
We regard none of the four factors identified ... as either a necessary or sufficient condition to the finding of a deprivation of the right of a speedy trial. Rather, they are related factors and must be considered together with such other circumstances as may be relevant. . [Cjourts must still engage in a difficult and sensitive balancing process. [Id. at 533, 92 S.Ct. at 2193; footnote omitted.]
It is true that appellant’s counsel asserted the right before trial but when balanced against the reasons for the delay and the lack of prejudice to the defendant, the scale tips for the government. While part of the delay was due to court congestion which must be weighed against the government, Barker v. Wingo, supra at 531, 92 S.Ct. 2182, a substantial part of the delay can be attributed to the fact that there were two other outstanding indictments against appellant. Appellant was represented by the same attorney in all three cases, and the record indicates the cases were scheduled together on the court’s calendar. The initial trial date, April 11,1974, was continued on request of appellant’s counsel.' On July 30, 1974, the government requested a continuance because a key witness had failed to appear. The court indicated it would dismiss the case that afternoon if the government was unable to proceed. At this time the court also inquired of defense counsel whether he was going to object to a new indictment filed by the government in another case.4 After counsel indicated he would not, the government located the witness and announced it was ready to proceed. Appellant’s attorney then changed position and obtained a continuance in order to file a motion to dismiss the indictment on the ground that it was improperly returned. On August 21, 1974, appellant’s motion was heard and denied. On that same day, appellant’s attorney withdrew in all three cases. After a second counsel, was appointed for appellant the cases proceeded in an expeditious manner. Appellant cannot be heard to say that delay caused by his other trials should be held against the government.5
Finally, we find no prejudice to the defendant in the delays in this trial. Some of his witnesses were discredited, but not by a showing that their memories had failed. His witnesses testified in considerable detail, and one of appellant’s alibi witnesses appears to have been discredited somewhat for having remembered too much detail.
Under these circumstances, we conclude there was no denial of appellant’s right to a speedy trial.
II. Lack of Sua Sponte Instruction After Impeachment
Appellant also contends that the trial court erred in failing to give sua sponte a cautionary instruction with respect to the limited admissibility of a prior incon*457sistent statement used to impeach a defense witness. As counsel did not request such an instruction either at the time of the testimony or when the court instructed the jury, as required by Super.Ct.Cr.R. 30,6 we are precluded from reversing unless such failure amounts to plain error within the meaning of Super.Ct.Cr.R. 52(b). This court recently held in Johnson v. United States, D.C.App., 387 A.2d 1084 (en banc) (1978), that it was not plain error under the circumstances of that case for a trial judge to fail to give sua sponte an immediate cautionary instruction when a witness has been impeached by a prior inconsistent statement. Appellant argues, however, that prior statement in this case was subject to misuse by the jury and the trial court’s failure to act sua sponte to insure that the jury understood the limited purpose for the admission of the statement constitutes plain error.
Here there was little problem of jury confusion. The prosecutor made it quite clear at the time of cross-examination that he was using the statement for impeachment purposes.7 The trial court would have been better advised to give an immediate instruction informing the jury of the limited purpose for which the evidence was admissible. It is an elementary procedure with some trial judges. But we do not find the failure to do so here prejudicial to the defendant’s case so as to compel the conclusion there was plain error.
Since the witness’ prior statement was given under oath before the grand jury, we find appellant’s argument less convincing than the argument advanced in Johnson v. United States, supra. The recently-enacted Federal Rules of Evidence provide that a statement is not hearsay if
[t]he declarant testifies at the trial or hearing and is subject to cross-examination concerning the statement, and the statement is (A) inconsistent with his testimony, and was given under oath subject to the penalty of perjury at trial, hearing, or other proceeding . . . [Rule 801(d)(1); emphasis added].
While not binding here, in federal court the failure to give a cautionary instruction as to the limited relevance of the prior statement would not have been error at all, let alone plain error. One would have to consider the federal judiciary has gone far afield in the reasoning underlying its rule in order to conclude, as the dissenting opinion does, that there was plain error here.
We might say in passing that, as exemplified by enactment of the federal rule, the traditional view that prior inconsistent statements are hearsay and inadmissible as substantive evidence has come under attack in recent years. One leading commentator has stated:
It is hard to escape the view that evidence of a previous inconsistent statement, when declarant is on the stand to explain it if he can, has in high degree the safeguards of examined testimony. Allowing it as substantive evidence pays an added dividend in avoiding the ritual of a limiting instruction unlikely to be heeded by a jury. McCormick, Evidence § 251 at 603-04 (2d ed. 1972).
We find no grounds for reversal on the failure of the trial court to give the instruc*458tion where none was requested. Johnson v. United States, supra.
III. Alibi Instructions
Appellant alleges that in reinstruct-ing the jury on the defense of alibi the trial court improperly shifted the burden to appellant to establish his innocence. During deliberations the jury requested further instructions with respect to the alibi defense.8 After considerable discussion with counsel, the judge, over the objection of defense counsel, gave the following instruction to the jury:
The Government has offered evidence in the hopes of persuading you that they have carried their burden of proving beyond a reasonable doubt that the defendant was present at the time and place alleged in the indictment.
The defendant, however, contends that the Government has not carried its burden of proof because the defendant contends that he was somewhere other than the place and time alleged in the indictment.
If this evidence of the defendant, considered in its entirety, is sufficient to cause you to have a reasonable doubt as to whether the defendant was present at the time and place alleged, you must find the defendant not guilty.
If, on the other hand, the evidence of alibi, considered in its entirety, does not cause you to have a reasonable doubt as to whether the defendant was present at the time and place alleged in the indictment, then you may find the defendant guilty, assuming, of course, that you are satisfied beyond a reasonable doubt that the Government has proved all the other essential elements of the offense.
I hope I have answered your question. If I have not, I will entertain another question. You want to go back to the jury room and see if this does the job?
This instruction does not shift the burden to the defendant to prove his alibi.9 The judge stated that the government had the burden of proving beyond a reasonable doubt that defendant was present at the time and place alleged in the indictment and if the alibi evidence was sufficient to cause the jury to have a reasonable doubt as to the first fact it must find the defendant not guilty.
The two cases which appellant relies upon are distinguishable. In United States v. Scott, 174 U.S.App.D.C. 96, 529 F.2d 338 (1975), the Court of Appeals reversed a conviction because the trial court gave the following instruction:
Intoxication is not an excuse for the commission of a crime. Voluntary drunkenness is no defense to a criminal act unless specific intent or knowledge is an element of the offense; then drunkenness may be shown to prove mental incapability to form the specific intent. [Id. at 98, 529 F.2d at 340 (emphasis in original).]
The trial court had rejected a commonly accepted instruction and instead gave that questionable one, to which objection was made by defense counsel. The court concluded that the instruction given could well have been understood by the jury to place *459the burden on the defendant to establish lack of specific intent.
In United States v. Alston, 179 U.S.App.D.C. 129, 551 F.2d 315 (1976), credibility was crucial in the ease and appellant relied upon an alibi. Viewing the instructions in their entirety, the court concluded they did not adequately inform the jury that the defense “alibi evidence need only raise a reasonable doubt in their minds that the defendant was present at the crime scene; that they must consider the evidence in its totality, including the alibi evidence, in deciding the defendant’s guilt; and that the burden of proof never shifts.” Id. at 133, 551 F.2d at 319 (footnotes omitted).
Taken as a whole, the instructions here do not have those deficiencies. As a matter of fact, the questioned reinstruction on alibi, which had been requested by the jury, specified that before finding the defendant guilty the jury must be “satisfied beyond a reasonable doubt that the Government has proved all the other essential elements of the offense.” We consider that the instructions in this case were not prejudicial to appellant.
IV. Motion for a New Trial
Finally, appellant alleges that the trial court abused its discretion in refusing to order a new trial because the verdict was clearly contrary to the weight of the evidence. In addition, he argues that a new trial should have been granted on the ground of newly discovered evidence.10
In reviewing a trial court’s denial of a motion for new trial, we must give great weight to the trial judge’s ability to judge the credibility of the witnesses and to observe their demeanor. An appellate court should not reverse the trial court unless there has been a clear abuse of discretion. United States v. Anderson, 165 U.S.App.D.C. 390, 509 F.2d 312 (1974), cert. denied, 420 U.S. 991, 95 S.Ct. 1427, 43 L.Ed.2d 672 (1975); C. Wright, Federal Practice and Procedure — Criminal § 557 (1969). On review of the record it appears to us that the verdict was not clearly contrary to the weight of the evidence.11 Thus, the trial court did not abuse its discretion in denying the motion.
Appellant’s second argument is that there is newly discovered evidence which mandates that he be given a new trial. We agree with the trial judge, however, that the grant of this motion “would not be in the interest of justice, but would be a travesty of justice.” At the hearing on the motion for a new trial appellant produced additional witnesses who testified that appellant was not Johnson’s assailant. We find it significant that appellant claims he found four witnesses within a week after the trial while at the same time he argues that he was prejudiced by the fourteen months delay between his arrest and trial. While his attorney may not have known about these witnesses, appellant had information which would have led the attorney to them within that time.12 Additionally, at trial he chose not to introduce one poten*460tial witness who was present in the courtroom.
A new trial should be granted only when evidence which the defendant could not have known about through diligent search comes to light after trial. Heard v. United States, D.C.App., 245 A.2d 125 (1968). It is not a second chance for a trial. The evidence which appellant brought forward after trial was not “newly discovered” and there was no showing of exceptional circumstances which in the interest of justice would warrant a new trial. Huggins v. United States, D.C.App., 333 A.2d 385 (1975). Accordingly, we do not find that the trial judge abused his discretion in denying the motion for new trial.
Appellant’s conviction is
Affirmed.
. Only the conviction for assault with intent to commit robbery while armed is appealed. The conviction on assault with a dangerous weapon was vacated by the trial judge as having merged with the first count.
. “Bam” is a street name for the amphetamine, phenmetrazine.
. In fact, delays of over 30 months have been upheld, e. g., United States v. Lynch, 163 U.S. App.D.C. 6, 499 F.2d 1011 (1974); United States v. Ransom, 151 U.S.App.D.C. 87, 465 F.2d 672 (1972).
. This indictment originated out of another felony case in which appellant had a codefendant. The new indictment was identical in all respects as to appellant; the only language changed was one count relating to his code-fendant.
.See also § 2.3(a) of the American Bar Association Standards Relating to Speedy Trial, which states that the period of delay resulting from other proceedings concerning the defendant should be excluded in computing the time for trial.
. Rule 30 provides in part:
No party may assign as error any portion of the charge or omission therefrom unless he objects thereto before the jury retires to consider its verdict, stating distinctly the matter to which he objects and the grounds of his objection. . . . [Emphasis added.]
. The prosecutor asked the witness if she had been threatened. When the witness replied “no,” the prosecutor introduced the witness’ grand jury testimony in which she had stated, “This dude or friend, I guess, of Dexter walked up to me and told me that if I told anything on Dexter, I would be in trouble . . . I have no reason to lie. He [Forbes] wasn’t down there the night Clarence got shot.” After the witness stated she did not remember saying anything about being threatened and that she had not been threatened, the prosecutor continued:
Q. If you said that, you would have been lying under oath?
A. If I would have said that, yes.
Q. Or is it today?
A. What today?
Q. Are you lying under oath today?
A. No, I’m not lying. I have no reason to lie.
. The foreman of the jury requested the rein-struction and explained their confusion by stating:
I think, Your Honor, our question springs from when the counsel for the Government, Mr. Bullock, was summing up. There was a controversy about a point he made on the law with respect to alibis. You ruled you would give us more detail.
I think the issue we’re confused about, if our judgment is, let’s say, to reject the defendant’s alibi to some degree, does the law then say we, in effect, are rejecting the entire alibi and conversely, if there are some elements of the alibi that we find acceptable, how does that affect our judgment as far as the law with respect to the validity of the alibi as a whole?
It appears that the confusion was due to a statement made by the prosecutor in his final argument. The statement was to the effect that even though it had no burden to do so, the government had proven beyond a reasonable doubt that defendant’s alibi was false.
. Appellant did not explain in his brief why he considered that the instructions placed the burden on him.
. Rule 33 of the D.C. Rules of Criminal Procedure states:
The court on motion of a defendant may grant a new trial to him if required in the interest of justice. ... A motion for a new trial based on the ground of newly discovered evidence may be made only before or within two years after final judgment . . A motion for a new trial based on any other grounds shall be made within 7 days after verdict or finding of guilty or within such further time as the court may fix.
. Appellant makes much of the fact that he had more persons testifying in his defense than the prosecution had testifying against him. The jury apparently was unimpressed with the numbers and chose to believe the prosecution’s witnesses. This they were free to do. Most of the defense’s witnesses were eventually discredited in one way or another.
.The four new witnesses are Eddie Gardner, proprietor of Fast Eddie’s, Ralph Sims, Joseph Johnson and Ronald Epps. Ralph Sims admitted at the hearing on the motion that he visited the appellant in jail several times, and he told Joe Johnson of appellant’s arrest. Eddie Gardner as proprietor of Fast Eddie’s was a person known to the appellant and according to his testimony at the hearing could have added little to the defense case for he only had a glimpse of the back of the man who he thought shot Mr. Johnson.