Does a defendant have an obligation to object to a jury instruction that precluded the jury from independently determining the existence of a peace officer?

Furthermore, our law does not require an accused to object to erroneous jury instructions. (Pen.Code, 1259.) Defendant was therefore under no obligation to object to the erroneous instruction that precluded the jury from independently determining the existence of the "peace officer" element of the offense with which defendant was charged. "[A] fact becomes undisputed in a criminal trial only if the defense affirmatively concedes it." (People v. Harris, supra, 9 Cal.4th at p. 458, fn. 2, 37 Cal.Rptr.2d 200, 886 P.2d 1193 (conc. & dis. opn. of Kennard, J.).) Thus, contrary to the majority's assertion, defendant did not by his silence "effectively" acquiesce in, agree with, or concede to the giving of the modified instruction.