concurring in part and dissenting in part:
I join in Parts I., II.A., and II.B. of the majority opinion and thus vote to affirm Walker’s conviction. However, I respectfully dissent from Part II.C. of that opinion. Because (1) the trial court did not adequately explain its ruling in refusing to *668admit some of the defense-proffered testimony of Angelic Elliott, and because (2) I cannot say from this record that the proffered testimony was inadmissible as a matter of law, and because (3) any error in refusing to admit the evidence could not have been harmless, I would remand the record for a clear trial court ruling on admissibility before deciding whether to affirm or reverse Abney’s conviction.
I.
There was powerful testimony — including testimony from defense witnesses— that Abney had a motive for aiding and abetting Walker in the stabbing death of John Smith. A defense witness, Angelic Elliott, testified at trial that appellant Ab-ney, upon returning to the house after Smith had been stabbed, gave a reason for what had happened. According to Elliott, “before we found out that [John Smith] was stabbed ... somebody said well, Andre [Abney,] why did you do that. And then he said because I — I didn’t forget what he had — what he had done to me.” Others testified that, back inside the house, when asked what happened, Abney referred to a “pole incident” — to what “John [Smith] did to him with the pole.” More specifically, the prosecutor’s colloquy with defense witness Diane Abney revealed: “Q[:] And did he hit him [with the pole]? A.[:] I guess so.”
The defense, however, proffered additional testimony by Angelic Elliott that would have undercut the evidence that Ab-ney had aided and abetted a killing, in contrast with a lesser assault. Defense counsel proffered that Elliott would further testify that Abney, upon returning to the house after Smith had been stabbed, also “stated that he did not know that John [Smith] had been stabbed and that he was going to get [Walker] back.” That evidence was consistent with Abney’s own testimony that he had tried to help John Smith by picking him up after Walker had struck him, and that when Walker approached again, as Abney held Smith, Ab-ney could see “hand movement” but could not “see if he had struck him or not” because Smith’s head was obstructing Ab-ney’s view.
Taking all of Angelic Elliott’s testimony together, defense counsel could have argued that, even if the jury did not believe Abney was trying to help Smith but instead was trying to avenge the “pole incident,” Abney at most knowingly helped Walker beat up Smith; Abney did not knowingly help kill him. The trial court, however, refused to admit the proffered testimony because it was a “self-serving declaration.” The court apparently rejected the prosecutor’s objection that the statement was inadmissible hearsay. The court said, “I could think of — I could think of at least two reasons that I could let it in. However, I don’t think it’s favorable to your [the government’s] case to keep it out and I think that it does bolster what I see as an otherwise frivolous motion for a severance and I’m going to keep it out.”
The trial court’s analysis is troublesome. If the court believed the severance motion was “otherwise frivolous,” the court was indicating that it believed the proffered testimony might have sufficiently implicated Walker to tip the balance in favor of a severance. If that was the court’s reasoning, based on its continuing obligation to guard against prejudice from joinder, see Hordge v. United States, 545 A.2d 1249, 1257-58 (D.C.1988), the court had an equal duty to guard against prejudice to Abney from joinder by making sure not to rule out probative evidence in his favor. Indeed, when a collision of interests occurs at trial “as a result of joinder,” causing “undue prejudice” to either party, the court has an obligation to grant a severance. Id. at 1257.
We must assume that the trial court was as alert to protecting Abney from joinder as it was concerned about protecting Walker. Moreover, we cannot simply ignore the trial court’s apparent belief that the proffered testimony was technically admissible, as against a hearsay objection, “for at least two reasons.” Thus, we are left with the court’s ruling against admission of that evidence on the ground that, given the likely prejudice against Walker, Abney had no *669countervailing, protectible interest in admission of a “self-serving declaration.”
I am not aware of any evidentiary rule in this jurisdiction that would preclude admission of a statement merely on the ground it is a “self-serving declaration.” 1 Apparently, my colleagues also are unaware of such a rule, for they assume that the court must have been ruling out admissibility on hearsay grounds. I am not so confident that this was what the trial court was doing. The court’s words effectively repudiated the prosecutor’s hearsay objection. Moreover, I do not believe that the proffered testimony necessarily would fail to meet the “spontaneous utterance”2 or “state of mind”3 exceptions to the hearsay rule. Abney rushed into the house moments after the stabbing. He testified, without contradiction, that he was crying and upset upon discovering from others inside the house that his brother had been stabbed. See ante at n. 7. That news, not the fight itself, could have been a startling event causing nervous excitement leading immediately to a spontaneous and sincere statement that Abney did not know Smith had been stabbed and that he was going to get Walker back. If so, the alleged hearsay would have been a classic spontaneous utterance. See supra note 2. Moreover, it might have reflected a state of mind, relevant here, showing surprise and anger and thus revealing ignorance of a stabbing (in contrast with a beating) while the attack was taking place. See supra note 3.
On this record, and particularly in light of the trial court’s own apparent rejection of the government’s hearsay objection, I cannot join my colleagues in holding as a matter of law that the proffered testimony did not fall within an exception to the hearsay rule and was therefore inadmissible. On the other hand, because I cannot say as a matter of law on this record that the proffered testimony was admissible under an exception to the hearsay rule or otherwise, I believe that the record in Abney’s case should be remanded to the trial court for clarification of its exclusion of the evidence. We would then be in a position to rule.
Such a remand, of course, would be unnecessary if we could conclude that any error here was harmless. I cannot do that. Although there was plenty of testimony tending to show that Abney held Walker while Walker stabbed Smith, only one piece of evidence — testimony by a medical examiner — tended directly to refute Abney’s testimony that he could not see what was going on because Smith’s head blocked his view.4 I do not think we can say that this expert testimony was enough to take from the jury the issue of what Abney could see, and thus what Abney knew about the nature and severity of the beating. If the proffered testimony was erroneously excluded, Abney was entitled to have the jury consider his credibility as against the expert’s.
Furthermore, the excluded statement by Abney proffered through Angelic Elliott would not necessarily have been inconsistent with Abney’s admission, reported by Elliott and others at trial, that he had “not forgotten” what Smith “had done to me” (the pole incident). Even if Abney lied in testifying that he was trying to help Smith, that lie did not necessarily mean he was *670knowingly assisting in a revenge killing rather than a revenge beating. In short, the evidence is too inconclusive for a finding of harmless error as to Abney’s knowledge and state of mind at the time he was holding Smith.5
II.
On remand, I would have the trial court rule on the admissibility of the defense-proffered testimony of Angelic Elliott in light of the considerations expressed above. If the court were to rule the testimony admissible, and we were to sustain that ruling, we should order a new trial.6 If the trial court were to rule the testimony inadmissible, we would of course either affirm or reverse and remand for- a new trial, depending on our view of the court’s ruling.
. See 2 John William Strong et al.. McCormick on Evidence § 270, at 209-11 (4th ed. 1992) (footnote omitted):
The hearsay rule excludes all hearsay statements unless they fall within some exception to the rule. Thus, no specific rule is necessary to exclude self-serving out-of-court statements if not within a hearsay exception....
[Judgments about credibility should generally be left to the jury rather than preempted by a judicial determination of inadmissibility. This is particularly true when the credibility issue can be readily appreciated by the jury, as is generally the case when the reason to question credibility rests upon the declarant’s self-serving motivation.
. See, e.g., Price v. United States, 545 A.2d 1219, 1226 (D.C.1988); Nicholson v. United States, 368 A.2d 561, 564 (D.C.1977).
. See, e.g., Nelson v. United States, 601 A.2d 582, 596 (D.C.1991); Giles v. United States, 432 A.2d 739, 745 (D.C.1981).
. The medical examiner testified that, based on the types of wounds Smith received, he must have been doubled over.
. Because Angelic Elliott’s proffered testimony was not admitted in evidence at the joint trial and thus did not prejudice Walker, it has no bearing on Walker’s conviction, and any severance issue in light of the possible admissibility of that proffered testimony is now moot.
. If the trial court found the proffered testimony admissible, the trial court would not go on to opine on harmless error; that is exclusively an appellate court function. See Davis v. United States, 564 A.2d 31, 41-42 (D.C.1989) (en banc). In this case, having ruled on harmless error before remand, we would not repeat that exercise after remand.