Background
Jenny M. Nguyen shot and killed her boyfriend following a volatile and violent relationship. Part of the incident was captured by her home surveillance system. Afterward, Nguyen deleted some surveillance footage and tried to hide her gun.
The prosecution charged Nguyen with first degree murder and two counts of tampering with physical evidence. Her defense expert, a licensed marriage and family therapist, diagnosed her with PTSD. Although the trial court allowed the therapist to testify about trauma, domestic violence, and Nguyen’s history, it barred testimony about the PTSD diagnosis. A court-appointed forensic psychiatrist testified that Nguyen did not have PTSD. The jury acquitted Nguyen of first degree murder but convicted her of reckless manslaughter and both tampering counts.
The Court’s Holding
The Colorado Court of Appeals reversed all convictions and remanded. It held that the trial court abused its discretion under CRE 702 by excluding the therapist’s PTSD diagnosis. The therapist’s education, training, and decades of experience treating trauma and domestic-violence victims sufficiently qualified her to diagnose PTSD; CRE 702 did not require a particular degree or PTSD-specific credentials.
The exclusion also violated Nguyen’s constitutional right to present a complete defense. The diagnosis was her only direct response to the prosecution expert’s opinion that she did not have PTSD, and it bore on her mental state for both reckless manslaughter and intentional tampering. The Attorney General did not show beyond a reasonable doubt that the error did not contribute to any conviction.
Key Takeaways
- Expert qualification under CRE 702 is liberal and may rest on knowledge, experience, education, or training.
- A defense-selected expert need not be a psychiatrist or psychologist merely to offer a mental-health diagnosis.
- Excluding the sole direct rebuttal to prosecution expert evidence on a central issue can violate the constitutional right to present a complete defense.
Why It Matters
The decision underscores that courts must distinguish between the weight of a mental-health expert’s diagnosis and the threshold question whether the expert is qualified to give it. When the diagnosis directly bears on the defendant’s culpable mental state, wrongful exclusion may require reversal under the constitutional harmless-error standard.