What is the basis for trial counsel's decision not to put on a diminished capacity defense?

The record does not show the basis for trial counsel's decision not to put on a diminished capacity defense, or whether he investigated or failed to investigate such a defense. Counsel's failure to object to the instruction may have been a result of a misunderstanding of the effective date of the abolition of the defense of diminished capacity, as defendant argues, but it could equally have been the result of a determination that there was no meritorious diminished capacity defense to be made. Whether this evaluation of the diminished capacity defense was a competent decision or not does not appear on the record, and any argument on this point must be raised by way of petition for writ of habeas corpus. (See People v. Pope, supra, 23 Cal.3d at p. 426, 152 Cal.Rptr. 732, 590 P.2d 859.) ¹⁴