Tenn. Code Ann. § 8-20-103: Requirements for authorization

(a) No deputy or deputies or assistants shall be allowed to any office, unless the actual officer is unable to personally discharge the duties of the office by devoting such officer's entire working time thereto, except field deputy sheriffs.

(b) In case the officer is incapacitated from any cause to perform the duties of the office, one (1) person working in the place of the officer shall neither be considered nor paid as a deputy or assistant.