Cal. Veh. Code § 40003
Whenever an employee is prosecuted for a violation of any provision of this code, or regulations promulgated pursuant to this code, relating to the size, weight, registration, equipment, or loading of a vehicle while operating a vehicle he was employed to operate, and which is owned by his employer, the court shall on the request of the employee take appropriate proceedings to make the owner of the vehicle a codefendant. In the event it is found that the employee had reasonable grounds to believe that the vehicle operated by him as an employee did not violate such provisions, and in the event the owner is found guilty under the provisions of Section 40001, the court may dismiss the charges against the employee.
In those cases in which the charges against the employee are dismissed, the abstract of the record of the court required by Section 1803 shall clearly indicate that such charges were dismissed and that the owner of the vehicle was found guilty under Section 40001.
Ca. Veh. Code § 40003