Cal. Gov. Code § 3521.5

The term “professional employee” means (a) any employee engaged in work (1) predominantly intellectual and varied in character as opposed to routine mental, manual, mechanical, or physical work; (2) involving the consistent exercise of discretion and judgment in its performance; (3) of such a character that the output produced or the result accomplished cannot be standardized in relation to a given period of time; (4) requiring knowledge of an advanced type in a field of science or learning customarily acquired by a prolonged course of specialized intellectual instruction and study in an institution of higher learning or a hospital, as distinguished from a general academic education or from an apprenticeship or from training in the performance of routine mental, manual, or physical processes; or (b) any employee, who (1) has completed the courses of specialized intellectual instruction and study described in paragraph 4 of subdivision (a), and (2) is performing related work under the supervision of a professional person to qualify himself to become a professional employee as defined in subdivision (a).