Tennessee Code Title 38. Prevention and Detection of Crime § 38-3-102

(a) The sheriff is the principal conservator of the peace in the sheriff's county. It is the sheriff's duty to suppress all affrays, riots, routs, unlawful assemblies, insurrections, or other breaches of the peace, to do which the sheriff may summon to such sheriff's aid as many of the inhabitants of the county as such sheriff thinks proper.

(b) It shall be the duty of the sheriffs, in their respective counties, by themselves or deputies, to patrol the roads of the county, to ferret out crimes, to secure evidence of crimes, and to apprehend and arrest criminals.