What is the test for evidence of mental impairment in a criminal case?

Like voluntary intoxication, "[e]vidence of mental disease, mental defect, or disorder shall not be admitted to show or negate the capacity to form any mental state," and it is only admissible "on the issue of whether or not the accused actually formed a required specific intent." ( 28, subd. (a).) CALCRIM No. 3428 conveys the substance of section 28. A trial court must give a mental impairment instruction "only if substantial evidence supports the defense theory that defendant's mental disease or disorder affected the formation of the relevant intent or mental state." (People v. Larsen (2012) 205 Cal.App.4th 810, 824.) "[E]xpert medical opinion testimony is necessary to establish that a defendant suffered from a mental disease, mental defect, or mental disorder within the meaning of CALCRIM No. 3428, because jurors cannot make such a determination from common experience." (Ibid.; see People v. Moore (2002) 96 Cal.App.4th 1105, 1117.)