California Code, Labor Code - LAB § 4060

(a) This section shall apply to disputes over the compensability of any injury. This section shall not apply where injury to any part or parts of the body is accepted as compensable by the employer.

(b) Neither the employer nor the employee shall be liable for any comprehensive medical-legal evaluation performed by other than the treating physician, except as provided in this section. However, reports of treating physicians shall be admissible.

(c) If a medical evaluation is required to determine compensability at any time after the filing of the claim form, and the employee is represented by an attorney, a medical evaluation to determine compensability shall be obtained only by the procedure provided in Section 4062.2.

(d) If a medical evaluation is required to determine compensability at any time after the claim form is filed, and the employee is not represented by an attorney, the employer shall provide the employee with notice either that the employer requests a comprehensive medical evaluation to determine compensability or that the employer has not accepted liability and the employee may request a comprehensive medical evaluation to determine compensability. Either party may request a comprehensive medical evaluation to determine compensability. The evaluation shall be obtained only by the procedure provided in Section 4062.1.

(e) The notice required by subdivision (d) shall be accompanied by the form prescribed by the administrative director for requesting the assignment of a panel of qualified medical evaluators.