The New Mexico Supreme Court heard arguments Monday in an appeal of a murder case that could force the state’s district court system to consider the question of whether a “warrior gene” might make some people prone to impulsive acts of violence.
If the court sends the case back to the state’s First Judicial District Court for consideration, a Santa Fe man convicted and jailed for second-degree murder would have a chance to argue the gene played a role in his killing of a man in October 2012.
That could alter his sentence, his lawyer said. It also could set a precedent in New Mexico and provide an example to courts around the nation on how to apply new and novel theories about behavioral genetics.
Several of the justices questioned what message it would send to move the case back to District Court at this point before Chief Justice Judith K. Nakamura said the court would take the matter under advisement.
If the court rejects the appeal, it could quash all such notions, at least for the time being.
The warrior gene theory has been fiercely debated since a Dutch scientist discovered in the early 1990s that all the male relatives in a New Zealand family with a history of aggressive violence lacked a specific gene critical for regulating anger.
The theory — that people with low levels of a certain enzyme, who also are abused as children, are prone to impulsive violence — has been used as a murder defense twice in the United States.
One of those cases was in Santa Fe in 2015, when the public defender for Anthony Blas Yepez, accused of first-degree murder, attempted to introduce evidence and have a jury listen to expert witness testimony on the topic to cast doubt on Yepez’s ability to form the intent required to convict him of the first-degree charge.
At that time, state prosecutors said the expert testimony did not comport with studies and science on the issue. District Judge Mary Marlowe Sommer did not allow the jury to hear expert testimony on the warrior gene.
The jury convicted Yepez of second-degree murder, tampering with evidence and unlawful taking of a motor vehicle.
Attorney Linda Helen Bennett told Supreme Court justices Monday that as a result, Yepez was denied the right to provide evidence that would have allowed the jury to consider whether a warrior gene influenced his actions.
The science behind the theory may not yet be “settled,” Bennett said following the hearing, but “that’s not grounds to keep it out of the courtroom. It’s grounds for ‘Let the jurors consider the evidence.’ Let’s put it in front of the jurors, let them run it up the flagpole and see what they say.”
She said her argument goes beyond ensuring her client received a fair trial. The warrior gene theory, she said, could become the “wave of the future” in courtroom cases involving aggressive behavior and acts of violence.
But Assistant Attorney General Maris Veidemanis countered that the appeal is problematic because Yepez wanted to use the warrior gene argument to fend off a first-degree murder charge, thus making any effort to revisit the case on a second-degree murder charge “irrelevant.”
Both sides filed also subsequent briefs arguing whether a Court of Appeals ruling that found Marlowe “erred” in her ruling has merit.
The appeal ruling of July 24, 2018, cites Adrian Raine, an expert in neurocriminology, as testifying in a hearing tied to the case that “30 percent of humans” have this low-functioning warrior gene.