In California, it is well settled that a writ of habeas corpus ordinarily may not be employed as a substitute for an appeal. Absent unusual circumstances, an aggrieved party should first appeal before resorting to habeas corpus. In this way, habeas corpus is preserved as an avenue of relief to those for whom the standard appellate system failed to operate properly. Proper appellate procedure demands that, absent strong justification, issues that could be raised on appeal must initially be so presented, and not on habeas corpus in the first instance. Accordingly, an unjustified failure to present an issue on appeal will generally preclude its consideration in a postconviction petition for writ of habeas corpus. ( In re Harris, 5 Cal.4th at pp. 828-829.)