Swett v. State, 431 P.3d 1135

Father Robert C. Swett was charged with aggravated child abuse after his five‑month‑old son suffered a skull fracture, subdural hematoma, and severe retinal hemorrhages; Swett admitted dropping the child but claimed the injury was accidental.
The State developed a child‑protection/medical case for abusive head trauma; its experts testified the injuries were inconsistent with a short accidental fall.
Pretrial, Swett demanded disclosure of other‑acts evidence under W.R.E. 404(b); the State sought to introduce prior violence against partners/children and a jail altercation that occurred after the charged conduct.
The trial court excluded testimony from former partners/children but admitted testimony about the jail fight (three witnesses) to prove intent, absence of accident, and motive, with a limiting instruction.
Swett was convicted by a jury and sentenced; on appeal he argued admission of the jail incident violated W.R.E. 404(b) and W.R.E. 401 (irrelevance).
The Wyoming Supreme Court held the jail‑incident evidence was admitted erroneously under Rule 404(b) (not sufficiently similar and motive not articulated) but that the error was harmless given the strength of the State’s other evidence.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Admissibility of "other acts" (W.R.E. 404(b))	State: jail altercation shows intent, lack of accident, and motive because Swett used an "accident" defense there too	Swett: jail incident dissimilar (adult victim, jail setting, different claimed accident); allows impermissible propensity inference	Court: Abuse of discretion to admit — incidents insufficiently similar; motive not articulated; 404(b) admission improper
Prejudice / Harmless error (W.R.Cr.P. 52)	State: error harmless because other overwhelming evidence showed non‑accidental abuse	Swett: jury likely prejudiced by other‑acts testimony and learning he was in jail	Court: Error harmless — no reasonable probability of a different verdict given strong medical evidence, inconsistencies in Swett's statements, witnesses on his conduct, limiting instruction, and minimal emphasis on the jail incident

Gleason v. State, 57 P.3d 332 (Wyo. 2002) (sets four‑part test for admissibility of 404(b) evidence)
Grabill v. State, 621 P.2d 802 (Wyo. 1980) (404(b) is a specialized relevancy rule; proponent must identify consequential fact and evidential hypothesis)
Goodman v. State, 601 P.2d 178 (Wyo. 1979) (discusses intent and relation to absence of accident)
United States v. Hogue, 827 F.2d 660 (10th Cir. 1987) (other‑acts inadmissible where no logical connection to show absence of accident; risk of propensity inference)
Wimbley v. State, 208 P.3d 608 (Wyo. 2009) (doctrine of chances / similarity of prior acts relevant when intent is at issue)
Garrison v. State, 409 P.3d 1209 (Wyo. 2018) (post‑offense other‑acts can be admissible under 404(b) where relevant)