Can someone be registered with the sexual offender registry only if charged with statutory rape or must there be a guilty verdict in a trial or plea bargain?

You must be "convicted" of a sex offense defined under TCA 40-39-202. Statutory Rape is listed as one of the offenses required to register; however, registration is only required under specific circimstances; meaning, not all statutory rape convictions would qualify as being "required" to register.

This section of the law is very long. Below is a few cuts from the actual law that covers Statutory Rape specifically.

40-39-202. Part definitions.

A “sexual offender” is any person who has been convicted in this state of committing a sexual offense as defined by T.C.A. 40-39-202 (17); or has another qualifying conviction as defined by T.C.A. 40-39-202 (2).

(17) “Sexual offense” means:
(A) The commission of any act that, on or after November 1, 1989, constitutes the criminal offense of:
(i) Sexual battery, under § 39-13-505;
(ii) Statutory rape, under § 39-13-506, if the defendant was an authority figure, as defined in § 39-13-527 (a)(3)(A) and (B), to the victim, or if the defendant has at least one (1) prior conviction for mitigated statutory rape under § 39-13-506(a), statutory rape under § 39-13-506(b), or aggravated statutory rape under § 39-13-506(c);

39-13-506. Statutory rape.

(a) Mitigated statutory rape is the unlawful sexual penetration of a victim by the defendant, or of the defendant by the victim when the victim is at least fifteen (15) but less than eighteen (18) years of age and the defendant is at least four (4) but not more than five (5) years older than the victim.
(b) Statutory rape is the unlawful sexual penetration of a victim by the defendant or of the defendant by the victim when:
(1) The victim is at least thirteen (13) but less than fifteen (15) years of age and the defendant is at least (4)four years older than the victim; or
(2) The victim is at least fifteen (15) but less than eighteen (18) years of age and the defendant is more than (5)five years older than the victim.
(c) Aggravated statutory rape is the unlawful sexual penetration of a victim by the defendant, or of the defendant by the victim when the victim is at least thirteen (13) but less than eighteen (18) years of age and the defendant is at least ten (10) years older than the victim.
(d) (1) Mitigated statutory rape is a Class E felony.
(2) Statutory rape is a Class E felony.
(3) Aggravated statutory rape is a Class D felony.
[Acts 1989, ch. 591, § 1; 1990, ch. 980, § 4; 1994, ch. 719, § 1; 2005, ch. 487, § 4; 2006, ch. 890, § 5.]

39-13-527. Sexual battery by an authority figure.

(a) Sexual battery by an authority figure is unlawful sexual contact with a victim by the defendant or the defendant by a victim accompanied by the following circumstances:

(1) The victim was, at the time of the offense, thirteen (13) years of age or older but less then eighteen (18) years of age; or

(2) The victim was, at the time of the offense, mentally defective, mentally incapacitated or physically helpless, regardless of age; and,

(3) (A) The defendant was at the time of the offense in a position of trust, or had supervisory or disciplinary power over the victim by virtue of the defendant's legal, professional or occupational status and used the position of trust or power to accomplish the sexual contact; or

(B) The defendant had, at the time of the offense, parental or custodial authority over the victim and used the authority to accomplish the sexual contact.

(b) Sexual battery by an authority figure is a Class C felony.
[Acts 1997, ch. 256, § 1; 1998, ch. 1034, § 1; 2005, ch. 478, § 1; 2006, ch. 897, § 1.]