State v. Thornton, 339 P.3d 112

In 2010–2011 Thornton lived in a home with Mother and her 12‑year‑old daughter (Child); forensic testing later found Thornton’s DNA in seminal fluid on clothing from Child’s room.
Child accused Thornton of repeated sexual assaults; she initially denied abuse but later reported it after learning Thornton was jailed. A medical exam showed an intact, elastic hymen; no rape kit was collected due to delay; pregnancy test was negative.
Thornton sought to admit evidence that Child was sexually active with another male contemporaneously; the district court excluded that evidence under Utah Rule of Evidence 412 and rejected constitutional challenges to that exclusion.
The State initially agreed before two trials to exclude evidence that Thornton supplied drugs to Mother and encouraged Mother’s prostitution; after two mistrials, the State sought and obtained admission of that evidence under Utah Rule of Evidence 404(b) at the third trial.
The jury convicted Thornton on multiple counts of child rape, sodomy, aggravated sexual abuse, and witness tampering; on appeal the court affirmed exclusion of the Rule 412 evidence but reversed convictions because the district court failed to scrupulously examine and balance the Rule 404(b) prior‑acts evidence.

Issue	Plaintiff's Argument (State)	Defendant's Argument (Thornton)	Held
Admissibility of Child’s other sexual activity under Utah R. Evid. 412	Exclusion appropriate under Rule 412; State may rely on other evidence of exposure to sexual conduct	Needed to show alternate source for Child’s belief she was pregnant and to rebut "sexual innocence" inference; exclusion violated confrontation/defense rights	Exclusion affirmed. Child’s pregnancy belief and sexual knowledge are not "semen, injury, or other physical evidence" under R.412(b)(1); Rule 412 exclusion did not violate constitutional rights given Child’s exposure to Mother’s prostitution.
Admissibility of Thornton’s supplying drugs and encouraging Mother’s prostitution under Utah R. Evid. 404(b)	Evidence relevant to explain why Thornton had power/trust in household and why Mother/Child did not stop him; allowed to fill contextual gap	Evidence was improper character propensity evidence and prejudicial; court failed to perform required scrupulous Rule 404(b) analysis	Admission reversed. Court abused discretion by combining distinct bad acts (drugs vs. prostitution) without separate 404(b)/402/403 analysis and failing the scrupulous balancing required by Verde.

State v. Verde, 296 P.3d 673 (Utah 2012) (trial courts must scrupulously examine and balance prior‑bad‑acts evidence under Rule 404(b))
State v. Lucero, 328 P.3d 841 (Utah 2014) (sets out multi‑step record analysis for admission of other‑acts evidence including 404(b), 402, 403, and conditional relevance under 104(b))
State v. Marks, 262 P.3d 13 (Utah Ct. App. 2011) (discusses rebutting the sexual‑innocence inference and limits on Rule 412 evidence)
State v. Moton, 749 P.2d 639 (Utah 1988) (upholding exclusion of sexual‑history evidence where other proof could show the victim’s sexual knowledge)
State v. Shickles, 760 P.2d 291 (Utah 1988) (enumerates factors for Rule 403 balancing of other‑acts evidence)
State v. Bluff, 52 P.3d 1210 (Utah 2002) (standard for reciting facts in appellate opinion)