In what circumstances will a jury be instructed on the burden of proving imperfect self-defense?

In the present case, the jury was instructed on the People's burden of proving the absence of imperfect self-defense. Because evidence of sudden quarrel or heat of passion sufficient to support a finding of voluntary manslaughter was lacking, the trial court had no sua sponte duty to instruct the jury on the People's burden of proving that provocation and heat of passion were lacking. Moreover, even if we were to find that error occurred, it would be harmless for the reasons stated in part IV.B., ante. (See Neder v. United States (1999) 527 U.S. 1, 19; People v. Flood(1998) 18 Cal.4th 470, 489-490, 502-503; People v. Tillotson (2007) 157 Cal.App.4th 517, 538-539.)