Tenn. Code Ann. § 20-12-105: Number of witnesses

(a) Not more than two (2) witnesses called to prove the same fact shall be taxed in any bill of costs against the losing party, except in case of witnesses called to attack or sustain the character of a witness or party.

(b) If more than the number of witnesses allowed are examined in proof of any particular fact, a motion shall be made at the term at which the cause is tried, and the court shall instruct the clerk as to the taxation of costs. The motion shall not be made afterwards without good cause shown.