Mistake as to victim's age not a defense.

Utah Code § 76-2-304.5, under Part 76-2-3: Defenses to Criminal Responsibility.

Utah Code § 76-2-304.5

76-2-304.5. Mistake as to victim's age not a defense.

(1) It is not a defense to the following offenses that the actor mistakenly believed the victim to be 14 years old or older at the time of the alleged offense or was unaware of the victim's true age: child kidnapping, Section; 76-5-301.1 rape of a child, Section; 76-5-402.1 object rape of a child, Section; 76-5-402.3 sodomy on a child, Section; 76-5-403.1 sexual abuse of a child, Section; 76-5-404.1 aggravated sexual abuse of a child, Section; 76-5-404.3 unlawful kissing of a child, Section; or 76-5-416.2 an attempt to commit an offense listed in Subsectionsthrough. (1)(a) (1)(g)

(2) It is not a defense to the following offenses that the actor mistakenly believed the victim to be 16 years old or older at the time of the alleged offense or was unaware of the victim's true age: unlawful sexual activity with a minor, Section; 76-5-401 sexual abuse of a minor, Section; or 76-5-401.1 an attempt to commit an offense listed in Subsectionor. (2)(a) (2)(b)

(3) It is not a defense to the following offenses that the actor mistakenly believed the victim to be 18 years old or older at the time of the alleged offense or was unaware of the victim's true age: human trafficking of a child for labor, Section; 76-5-308.5 human trafficking of a child for commercial sexual exploitation, Section; 76-5-308.6 aggravated human trafficking, Section; 76-5-310 aggravated human smuggling, Section; 76-5-317 unlawful sexual conduct with a minor, Subsection; 76-5-401.2(2)(a)(ii) patronizing a prostituted individual who is a child, Section; 76-5d-204 aggravated exploitation of prostitution, Section; or 76-5d-208 sexual solicitation by an actor offering compensation to a child in exchange for sexual activity, Section. 76-5d-211