Labor Code – LAB § 3708
In such action it is presumed that the injury to the employee was a direct result and grew out of the negligence of the employer, and the burden of proof is upon the employer, to rebut the presumption of negligence. It is not a defense to the employer that the employee was guilty of contributory negligence, or assumed the risk of the hazard complained of, or that the injury was caused by the negligence of a fellow servant. No contract or regulation shall restore to the employer any of the foregoing defenses.
This section shall not apply to any employer of an employee, as defined in subdivision (d) of Section 3351 , with respect to such employee, but shall apply to employers of employees described in subdivision (b) of Section 3715 , with respect to such employees.