Tennessee Code Title 40. Criminal Procedure § 40-23-114

(a) For any person who commits an offense for which the person is sentenced to the punishment of death, the method for carrying out this sentence shall be by lethal injection.

(b) Any person who commits an offense prior to January 1, 1999, for which the person is sentenced to the punishment of death may elect to be executed by electrocution by signing a written waiver waiving the right to be executed by lethal injection.

(c) The department of correction is authorized to promulgate necessary rules and regulations to facilitate the implementation of this section.

(d) If lethal injection or electrocution is held to be unconstitutional by the Tennessee supreme court under the Constitution of Tennessee, or held to be unconstitutional by the United States supreme court under the United States Constitution, or if the United States supreme court declines to review any judgment holding lethal injection or electrocution to be unconstitutional under the United States Constitution made by the Tennessee supreme court or the United States court of appeals that has jurisdiction over Tennessee, or if the Tennessee supreme court declines to review any judgment by the Tennessee court of criminal appeals holding lethal injection or electrocution to be unconstitutional under the United States or Tennessee constitutions, all persons sentenced to death for a capital crime shall be executed by any constitutional method of execution.  No sentence of death shall be reduced as a result of a determination that a method of execution is declared unconstitutional under the Constitution of Tennessee or the Constitution of the United States.  In any case in which an execution method is declared unconstitutional, the death sentence shall remain in force until the sentence can be lawfully executed by any valid method of execution.

(e) For any person who commits an offense or has committed an offense for which the person is sentenced to the punishment of death, the method of carrying out the sentence shall be by lethal injection unless subdivision (e)(1) or (e)(2) is applicable.  If subdivision (e)(1) or (e)(2) is applicable, the method of carrying out the sentence shall be by electrocution.  The alternative method of execution shall be used if: