State v. Michael DeCosta, 293 A.3d 297

Defendant Michael DeCosta was convicted by a Kent County jury of felony assault resulting in serious bodily injury; sentenced to 20 years; he appealed.
The assault occurred after a party; victim Joseph Napolillo was found bloodied in a parking lot, suffered a severe traumatic brain injury, and required prolonged hospitalization and rehabilitation.
Witnesses (Paulino and Migliori) saw DeCosta return to a van with bloody knuckles and heard him say he had "knocked someone out;" blood in the van matched DeCosta’s DNA.
Napolillo gave a police statement (transcribed by his mother) saying DeCosta had earlier hit a different person (Cloutier) the same night; Napolillo could not recall events at trial.
The trial justice admitted Napolillo’s statement—including the sentence about the Cloutier incident—under Rule 404(b) as evidence of DeCosta’s plan/scheme/intent toward Napolillo, with limiting jury instructions; defense objected under Rules 404(b) and 403.
The Supreme Court held the trial justice abused discretion admitting the Cloutier sentence under 404(b) but found the error harmless given the strength of the State’s case and affirmed the conviction.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Admissibility under Rule 404(b) of a witness statement that DeCosta hit Cloutier earlier that night	State: statement shows DeCosta’s state of mind/plan/scheme/intent that evening toward Napolillo and is admissible for that non‑propensity purpose	DeCosta: statement is impermissible propensity evidence of other bad acts; not relevant to intent toward Napolillo	Court: admission was an abuse of discretion—Cloutier incident not tied to intent toward Napolillo (404(b) misuse)
Rule 403 balancing—whether probative value was substantially outweighed by unfair prejudice	State: probative value for state of mind/plan and limited by jury instruction; not overly prejudicial	DeCosta: prejudicial effect substantially outweighed any probative value and warranted exclusion	Court: trial justice considered balance; though 404(b) admission was erroneous, the error was harmless beyond a reasonable doubt and conviction stands

State v. Ciresi, 45 A.3d 1201 (R.I. 2012) (prior uncharged conduct admissible for non‑propensity purposes under Rule 404(b))
State v. Martinez, 59 A.3d 73 (R.I. 2013) (prior assaults against same victim admissible to show intent/motive)
State v. Clements, 83 A.3d 553 (R.I. 2014) (trial justice must give limiting instruction when admitting 404(b) evidence)
State v. Mercurio, 89 A.3d 813 (R.I. 2014) (harmless‑error test: must be proof beyond a reasonable doubt that error did not contribute to verdict)
State v. Momplaisir, 815 A.2d 65 (R.I. 2003) (strength of prosecution’s case relevant in harmless‑error analysis)
State v. Garcia, 743 A.2d 1038 (R.I. 2000) (404(b) does not require exclusion merely because evidence suggests past criminal activity)