(a) If the employee of any common carrier shall receive any injury or shall be killed by reason of any defect in any cars, engines, motors, appliances, machinery, tracks, roadbeds, works, wharves, or other equipment owned, operated, or used by the common carrier, the common carrier shall be deemed to have had knowledge of the defect before and at the time the injury is sustained or death caused.
(b) When the fact of the defect shall be made to appear in the trial of any action in the courts of this state brought by the employee or his or her personal or legal representative against any common carrier for damages on account of injuries so received or death so caused, the fact of the defect shall be prima facie evidence of negligence on the part of the common carrier.