Does a cautionary instruction need to be given to the jury that a witness is in custody?

Defendant relies on the case of People v. Metzger (1904) 143 Cal. 447, 77 P. 155. In that case a defense witness was manacled by a deputy sheriff immediately after adjournment but in full view of the jury. The trial judge gave a cautionary instruction in regard to the fact that the jury should not be influenced in their decision by the fact that the witness was in custody. The reviewing court's opinion does not disclose whether or not the instruction was given on the court's own motion. The case was appealed on the theory that allowing the jury to see the witness handcuffed was prejudicial error because it unduly discredited him as a witness. The appellate court affirmed the decision pointing out the fact that the trial court cautioned the jury that they must not take the fact of handcuffing into consideration in determining their verdict. Defendant argues that the fact that in Metzger a cautionary instruction was given indicates that the court in the instant case should have given a cautionary instruction. This is a non sequitur.