Does a court have a duty to instruct a jury on a defendant's manslaughter instruction?

Although this case involves the trial court's refusal of a requested instruction rather than the possible existence of a duty to instruct on the court's own motion, the same reasoning applies here. As discussed earlier, defense counsel argued to the jury that the Arizona killing was the result of a sudden quarrel or heat of passion provoked by the victim's kicking defendant's dog. Defense counsel thereby presented to the jury a manslaughter-type argument in mitigation. As in People v. Cain, supra, 10 Cal.4th at page 73, 40 Cal.Rptr.2d 481, 892 P.2d 1224, the jury had before it the evidence and the argument from which it could rationally assess defendant's degree of culpability for the Arizona prior murder. The legal label, manslaughter, was not vital to this argument. It was therefore within the trial court's discretion to refuse defendant's manslaughter instruction and, because the instruction could have confused the jurors as to their task in the penalty phase, the court's refusal was not an abuse of discretion.