Ohio Revised Code Title XLIX. Public Utilities § 4973.06

No railroad company knowingly or negligently shall use or operate a car or locomotive that is defective, or upon which the machinery or attachments belonging to such car or locomotive are in any manner defective. If an employee of such company receives injury by reason of a defect in a car or locomotive, or the machinery or attachments belonging to such car or locomotive, owned and operated or being operated by such company, it shall be deemed to have had knowledge of such defect before and at the time such injury is so sustained. When such defect is made to appear in the trial of any action brought by such employee, or his legal representative, against a railroad company for damages on account of injuries so received, that fact shall be prima-facie evidence of negligence on the part of such company.