SANTA FE – The state Supreme Court today set aside the first-degree murder and evidence tampering convictions of a Las Vegas man for the stabbing death of a 71-year-old man in the northern New Mexico community in 2019.

The Court also ruled that the defendant, Seig Isaac Chavez, could be retried without violating his constitutional protections against double jeopardy.

In a unanimous opinion, the Court concluded that an audio recording of a telephone call Chavez made from jail to his son should not have been admitted as evidence during his trial and the recording "significantly affected the verdicts."

"The district court committed plain error by allowing the jury to hear evidence that was relevant only to Defendant's propensity for violence. This evidence was highly inflammatory and deprived Defendant of a fair trial," the Court wrote in an opinion by Justice C. Shannon Bacon.

Chavez was convicted of killing William "Skip" Smith, a developmentally disabled man who was well-known in Las Vegas and frequented businesses along one of the city's streets. His body was found in an alleyway. He had been stabbed 24 times, with wounds to his head, neck and other parts of his body.

A witness saw Smith getting into Chavez's truck on the evening of the killing. Upholstery from the truck's passenger seat later tested positive for the victim's blood and Smith's blood was found on the sleeve of a jacket at Chavez's home.

In the jail phone call, Chavez told his son he was now the "man of the house" responsible for protecting others and repeatedly instructed the teenager to stab anyone in the throat who got close to him or tried to touch him. He also told the son, "Daddy's going to prison."

The prosecutor mentioned the call in an opening statement at the trial, played the phone call in its entirety when presenting the state's evidence and then summarized the call and replayed it during closing arguments.

"In this case, the jury heard Defendant' own voice and words instructing his son to commit wanton, extreme acts of violence against other human beings. These instructions would give rise to aversion and dismay in any reasonable person," the Court wrote.

The law prohibits the use of evidence about a person's character when its sole purpose is to prove the individual's propensity to act in a certain way to commit the charged crime. The Court rejected arguments by the state that the jail phone call was admissible on other grounds, including that it was evidence of the defendant's "state of mind or intent."

The Court determined that one statement by Chavez in the phone call – "Daddy's going to prison" – could have a possible use as evidence because it "tends to show Defendant's consciousness of guilt." However, the justices concluded that the prejudicial effect on the jury from the phone call outweighed the limited evidentiary value of that isolated statement.

"We cannot overlook the power of this propensity evidence to sway the jury in this case," the Court reasoned.