People v. Harris, 2015 COA 53

In August 2005 Harris's stepson S.H. was found unconscious, later diagnosed with a left-sided subdural hematoma, and died on September 2; Harris was charged with first-degree murder, child abuse–resulting in death, and reckless endangerment.
Witnesses included Harris's children LL and O.W.; LL gave varying statements that Harris was upset and may have "thrown" or "whooped" S.H. the morning of August 22.
Medical experts conflicted: prosecution experts testified the injuries were consistent with high-impact non-accidental blunt trauma; Harris's expert attributed the fatal hematoma to a prior small accidental fall and a subsequent seizure.
The trial court admitted evidence of prior bad acts under CRE 404(b), including a 2003 car-chase incident in which Harris allegedly rammed a car containing an infant. The court limited use to absence of mistake/accident and Harris’s state of mind.
The jury acquitted on first-degree murder but convicted Harris of child abuse–resulting in death and reckless endangerment, finding both that she directly caused injury and permitted S.H. to be placed in a dangerous situation.
On appeal the court reversed and remanded for a new trial, concluding admission of the car-chase evidence was an abuse of discretion and not harmless given the close, contested forensic issues and the shaky child-witness evidence.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Admissibility of prior-act (car‑chase) evidence under CRE 404(b)	Car‑chase shows motive/intent, state of mind, absence of accident — relevant to recklessness/knowledge.	Car‑chase dissimilar to charged conduct; only shows propensity to get angry and disregard risk, thus inadmissible character evidence.	Reversed: admission was an abuse of discretion—incident not logically relevant to material issues (mental state/absence of mistake) and improperly invited propensity inference.
Harmless‑error analysis for erroneously admitted 404(b) evidence	Even if error, conviction should be affirmed because other evidence supported guilt.	Erroneous evidence likely influenced verdict given dueling medical experts and unreliable child testimony; error not harmless.	Reversed: error not harmless—reasonable probability that the car‑chase evidence contributed to conviction because the case was close.
Need for unanimity instruction	Prosecution argued alternative acts each could support conviction without requiring a special unanimity instruction.	Harris argued multiple discrete acts were alleged and jury must unanimously agree on specific act or be instructed accordingly.	Not decided on merits; court provided guidance: unanimity instruction required if evidence supports multiple discrete acts, not required if acts are a single transaction.

People v. Casias, 312 P.3d 208 (Colo. App. 2012) (framework for evaluating admissibility and prejudicial effect of other‑acts evidence; harmless‑error guidance)
People v. Spoto, 795 P.2d 1314 (Colo. 1990) (four‑part test for admissibility under CRE 404(b))
Yusem v. People, 210 P.3d 458 (Colo. 2009) (definition of material fact and logical relevance; harmless‑error standard)
United States v. Ince, 21 F.3d 576 (4th Cir. 1994) (discussing when strong properly admitted evidence may render erroneous evidence harmless)