State v. Thornton, 2017 UT 9

Defendant Robert Damien Thornton lived in a household where the 12‑year‑old victim (B.Z.) resided; prosecutors alleged he supplied the mother with drugs and encouraged her prostitution, creating access and control over B.Z.
B.Z. reported repeated rapes and sexual abuse by Thornton; physical testing found Thornton’s semen on a sweater but no contemporaneous medical evidence of rape or pregnancy.
Thornton was tried three times; the third trial resulted in conviction on multiple counts of rape, sodomy, and aggravated sexual abuse; evidentiary disputes centered on (1) admission of Thornton’s alleged drug‑ and prostitution‑related misconduct under Utah R. Evid. 404(b) and (2) exclusion of evidence of the victim’s prior sexual experience under Utah R. Evid. 412.
At the third trial the district court admitted the mother‑related misconduct evidence under 404(b) for non‑propensity purposes (narrative, access, power, and delay in reporting) with a limiting instruction; it excluded evidence of B.Z.’s consensual sexual relationship with a 14‑year‑old under Rule 412.
The Utah Court of Appeals reversed the conviction based on a perceived failure to perform a separate, "scrupulous examination" of two categories of 404(b) evidence (drug provision vs. encouragement of prostitution), but affirmed the Rule 412 ruling; the Utah Supreme Court granted certiorari.

Issue	Plaintiff's Argument (State)	Defendant's Argument (Thornton)	Held
Admissibility of prior misconduct under Utah R. Evid. 404(b)	Evidence was admissible for non‑propensity purposes (explained narrative: access, power, reason for delayed reporting); limiting instruction sufficed	Admission was improper; district court failed to perform required "scrupulous examination," and should have analyzed drug and prostitution evidence separately	Court reversed court of appeals; upheld district court admission — evidence had legitimate non‑propensity purpose, was relevant under Rule 402, and not substantially outweighed by prejudice under Rule 403; repudiated separate procedural "scrupulous examination" requirement
Exclusion of victim's prior sexual history under Utah R. Evid. 412 and Sixth Amendment	Exclusion appropriate; Rule 412 bars other‑sexual‑behavior evidence except narrow exceptions; prosecution did not treat victim as sexually innocent in a way that made exclusion unconstitutional	Evidence admissible under Rule 412(b)(1) as physical‑evidence source or under 412(b)(3)/Sixth Amendment as essential to confront witness and present defense	Court affirmed exclusion. 412(b)(1) inapplicable (no disputed forensic question about source of physical evidence). 412(b)(3)/Sixth Amendment not violated because Thornton failed to develop necessary trial‑record foundation showing the evidence was essential to his defense

State v. Decorso, 993 P.2d 837 (Utah 1999) (discussed prior guidance about careful 404(b) analysis)
State v. Lucero, 328 P.3d 841 (Utah 2014) (articulated three‑step 404(b)/402/403 analysis and referred to "scrupulous examination")
State v. Verde, 296 P.3d 673 (Utah 2012) (explained admissibility depends on avowed non‑propensity purpose and preservation issues)
State v. Widdison, 28 P.3d 1278 (Utah 2001) (procedural discussion of 404(b) analysis on the record)
Rock v. Arkansas, 483 U.S. 44 (U.S. 1987) (Sixth Amendment right to present a defense subject to reasonable evidentiary rules)
United States v. Scheffer, 523 U.S. 303 (U.S. 1998) (Sixth Amendment right is not absolute; evidentiary rules are permissible unless arbitrary or disproportionate)
Chambers v. Mississippi, 410 U.S. 284 (U.S. 1973) (Confrontation/compulsory‑process principles can require admission of defense‑critical evidence)
Washington v. Texas, 388 U.S. 14 (U.S. 1967) (Sixth Amendment protects the right to present witnesses in the defendant's favor)