What is the test for admitting to the Court of Appeal that a defendant admitted that he was a witness to the murder trial?

We decline to address the merits of this argument because we conclude the admission of this evidence was harmless under the standard of People v. Watson (1956) 46 Cal.2d 818, which allows reversal for evidentiary error only if it is reasonably probable a different outcome would have resulted in the absence of the error. (Id. at p. 836.) There was substantial direct and circumstantial testimony about the circumstances of the killing, most of it undisputed. Because defendant testified, the jury was able to evaluate his demeanor and credibility. In light of his testimony, the only truly disputed issue was his deliberation and planning, or lack thereof, an issue largely dependent on the events occurring prior to the beating.