When will a defense counsel not to present mitigating evidence at the penalty phase?

Defendant further contends that even if trial counsel's concern, that introduction of the mitigating evidence would open the door to admission of the prosecution's evidence of defendant's prior violent criminal activity, was not unreasonable when viewed from counsel's perspective at the time of trial, a tactical decision not to present the mitigating evidence nonetheless would fall below a standard of objective reasonableness because such a decision would leave the jury without any mitigating evidence to consider on defendant's behalf. Although mitigating evidence concerning the circumstances of a defendant's childhood and background often is of crucial importance at the penalty phase, providing information through which the jury can make an "individualized" determination as to the appropriate sentence (see In re Marquez, supra, 1 Cal.4th 584, 607-609, 3 Cal.Rptr.2d 727, 822 P.2d 435), defense counsel, in determining whether to present such information, properly may take [3 Cal.4th 615] into account the detrimental consequences that may result from the introduction of such evidence, including the nature of the evidence that the prosecution may elicit either on cross-examination of the proposed defense witnesses or on rebuttal. (See, e.g., People v. Miranda, supra, 44 Cal.3d 57, 120-122, 241 Cal.Rptr. 594, 744 P.2d 1127.)