428 P.3d 301
N.M. Ct. App.2018Background
- Victim was found dead in his apartment after an altercation among Victim, defendant Anthony Yepez, and Yepez's girlfriend; autopsy listed homicidal violence and thermal injuries. Yepez and Sandoval attempted to "dispose of evidence" and left in Victim's car; Yepez was later arrested. Sandoval pleaded guilty to second-degree murder.
- Yepez was charged with first-degree murder, tampering with evidence, and unlawful taking of a motor vehicle; at trial the jury convicted him of second-degree murder and the other offenses but acquitted him of first-degree murder.
- Yepez sought to admit expert testimony (neuropsychological and genetic) that he has a low-activity MAOA genotype combined with childhood maltreatment, which his experts said predisposed him to impulsive violence and impaired his ability to form deliberate intent.
- The State moved to exclude the proffered expert opinions under Rule 11-702 and Daubert/Alberico, arguing the MAOA-violence link and the impulsivity inference were not reliably established and risked juror confusion.
- The district court held a Daubert/Alberico hearing, found the underlying literature linking low MAOA + childhood maltreatment to antisocial/violent tendencies generally reliable, but excluded Dr. Walker's opinion as to Yepez's impulsivity because no witness directly interpreted the genetic test and the court viewed the impulsivity opinion as unsupported by the studies.
- On appeal the New Mexico Court of Appeals held the district court abused its discretion in excluding the impulsivity opinion (because reliability and relevancy review should focus on methodology not the weight of conclusions), but found the error harmless since the jury acquitted Yepez of first-degree murder and convicted him of second-degree murder (a general-intent offense that the MAOA evidence would not negate).
Issues
| Issue | State's Argument | Yepez's Argument | Held |
|---|---|---|---|
| Whether the district court properly excluded expert testimony under Rule 11-702/Daubert-Alberico (MAOA genotype + childhood maltreatment → predisposition to impulsive violence) | The literature does not reliably show a direct link to impulsive violence; testimony would mislead jurors and exceed experts' methodology | The experts were qualified, the underlying science met Daubert-Alberico, and the testimony was probative of inability to form deliberate intent | Court: Exclusion was an abuse of discretion; the methodology and underlying science were reliable enough that the jury should weigh the testimony's force |
| Whether exclusion of the expert testimony was prejudicial (requiring reversal/new trial) | Even if error, it was harmless because the MAOA evidence would not negate general-intent offenses and jury acquitted on first-degree charge | Proffered testimony was central to defense of specific intent and could have altered verdict on murder degrees | Court: Error harmless — jury acquitted of first-degree murder and convicted of second-degree (general-intent); no reasonable possibility excluded evidence affected verdict |
Key Cases Cited
- Daubert v. Merrell Dow Pharm., 509 U.S. 579 (trial-court gatekeeping focuses on principles and methodology, not conclusions)
- State v. Alberico, 116 N.M. 156, 861 P.2d 192 (N.M. 1993) (New Mexico Daubert-style framework for scientific expert admissibility)
- State v. Torres, 127 N.M. 20, 976 P.2d 20 (N.M. 1999) (Rule 11-702 prerequisites: qualification, assistance to trier, and domain limitation)
- State v. Anderson, 118 N.M. 284, 881 P.2d 29 (N.M. 1994) (factors for assessing scientific reliability)
- State v. Balderama, 135 N.M. 329, 88 P.3d 845 (N.M. 2004) (neuropsychological testimony that acts were impulsive can undermine deliberation required for first-degree murder)
- General Electric Co. v. Joiner, 522 U.S. 136 (courts may scrutinize analytical gaps between data and expert conclusions; New Mexico declined to adopt expansive Joiner gatekeeping)