Michael Jesse Munoz v. The State of Wyoming, 307 P.3d 829

Defendant was charged with one count of second‑degree and three counts of first‑degree sexual abuse of his 11‑year‑old niece; he pleaded not guilty.
Pretrial order required the State to give W.R.E. 404(b) notice; the State filed a 404(b) notice days before trial identifying an 18‑year‑old conviction (A.M.) for indecent liberties with a minor.
Defense moved to exclude the 404(b) evidence; the district court granted the motion before trial, ruling the prior conviction was unfairly prejudicial and primarily propensity evidence.
During voir dire and opening statements the defense tailored its strategy to the exclusion (including not cross‑examining the victim to avoid "opening the door").
After the State rested and without the victim having been cross‑examined, the court reversed its prior ruling and admitted A.M.’s testimony under W.R.E. 404(b) as probative of motive, identity, and corroboration; defendant argued this change deprived him of a fair trial.
The Wyoming Supreme Court held the mid‑trial reversal was an abuse of discretion because the record showed no new justification and the late admission unfairly prejudiced the defendant; conviction was reversed and case remanded.

Issue	State's Argument	Defendant's Argument	Held
Whether the district court abused its discretion by reversing a pretrial exclusion and admitting 404(b) evidence after the State rested	"Things changed" at trial: defendant denied guilt and attacked victim credibility, so the prior act corroborates motive/credibility and is admissible	Late reversal deprived defendant of fair trial; defense relied on exclusion in voir dire/opening and refrained from cross‑examining to avoid opening the door	Reversed: abuse of discretion where no new record justification existed and reversal unfairly prejudiced defendant

Thomas v. State, 131 P.3d 348 (Wyo. 2006) (abuse‑of‑discretion standard for 404(b) rulings)
Bromley v. State, 150 P.3d 1202 (Wyo. 2007) (definition of reasonable exercise of discretion)
Gleason v. State, 57 P.3d 332 (Wyo. 2002) (factors for admitting uncharged misconduct under Rule 404(b))
Hart v. State, 57 P.3d 348 (Wyo. 2002) (difficulties distinguishing propensity from corroborative uses of similar‑act evidence)
Parker v. State, 161 P. 552 (Wyo. 1916) (reversal required where fundamental and prejudicial error denies fair trial)