What is the test for an expert witness in a mental health case?

An expert may generally base his or her opinion on any "matter," personally known or made known to him, whether or not admissible, "that is of a type that reasonably may be relied upon by an expert in forming an opinion upon the subject to which his testimony relates . . . ." (Evid. Code, 801, subd. (b).) "Psychiatrists, like other expert witnesses, are entitled to rely upon reliable hearsay, including the statements of the patient and other treating professionals, in forming their opinion concerning a patient's mental state. [Citations.] On direct examination, the expert witness may state the reasons for his or her opinion, and testify that reports prepared by other experts were a basis for that opinion. [Citation.]" (People v. Campos (1995) 32 Cal.App.4th 304, 307-308.)

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