When will a judge order a competency hearing for a defendant in a mental health case?

By the same token, and absent a showing of "incompetence" that is "substantial" as a matter of law, the trial judge's decision not to order a competency hearing is entitled to great deference, because the trial court is in the best position to observe the defendant during trial. (Rogers, supra, 39 Cal.4th 826, 847.) " 'An appellate court is in no position to appraise a defendant's conduct in the trial court as indicating insanity, a calculated attempt to feign insanity and delay the proceedings, or sheer temper.' [Citations.]" (People v. Danielson (1992) 3 Cal.4th 691, 727.)