An employee who has an accumulated sick leave balance shall be authorized its use although recovery and return to duty is impossible. However, periodically, at the request of the appointing authority or representative, the disability or illness and inability to perform position requirements, must be certified to by a licensed physician or osteopath. No sick leave shall be authorized beyond mandatory retirement age under the Retirement System. (Added 1971, No. 231 (Adj. Sess.), § 1.)