An employee of a county board who is absent due to physical disability that results from an assault while in the scope of board employment shall be kept on full pay status instead of sick leave during the period of absence. Each county board shall establish rules and regulations for the entitlement and use of assault leave, including a requirement that an employee provide: A signed statement that justifies the use of assault leave; and If medical attention is required, a certificate from a licensed physician that states the nature and duration of the disability.