Then, one day in 2009, prosecutors say, he put a gun to the head of his 250-pound father and killed him at their Belen, N.M., home.
After years of stops and starts, the boy is scheduled to face a jury this month for first-degree murder in a rare prosecution expected to highlight the debate over whether children that young are capable of the pre-meditation required for such a serious charge. Experts say the boy, now 14 and living in Oklahoma, is just one of a handful of very young children in the nation's history to face such a conviction.
"I've been practicing law for 20 years and this is the saddest case I've ever seen," said the boy's attorney, William J. Cooley. "I don't know why this is even going to court."
Lemuel L. Martinez, 13th Judicial District Attorney, declined to talk about the case with The Associated Press. But he defended the decision to pursue the first-degree murder charge. "We are going to court because we believe we have enough evidence to meet the burden of proof," Martinez said.
The case is scheduled to go to trial Aug. 26 in a Valencia County courtroom, but defense attorneys want a change of venue and are seeking to have the 911 call made by the boy thrown out. His attorneys say the father, 42-year-old Byron Hilburn, had strong ties to law enforcement members in the area and that might taint a potential jury pool. They want the case moved to Sandoval County, north of Albuquerque.
The Associated Press is not naming the boy since he is being tried as a child in children's court.
If found guilty, the boy will be in state custody until he is 21 and must take part in a plan for rehabilitation.
There have been few other cases where young children have faced murder charges, according to the Robert Schwartz, executive director of the Juvenile Law Center in Philadelphia.
The most well-known example came in 1989 when Cameron Kocher, then 9, shot a 7-year-old playmate with a high-powered rifle in rural Pennsylvania after the playmate said she was better at the video game than he was. Kocher was tried as an adult but eventually pleaded no contest to involuntary manslaughter. He was placed on probation until he turned 21.
In 2000, a 6-year-old Michigan boy shot a first-grader at school with a gun he found at the house where he was living. The prosecutor declined to charge the boy, saying common law doesn't allow a child under the age of 7 to be held criminally responsible.
In California, a boy who was 10 when he fatally shot his white supremacist father was convicted in January of second-degree murder. Saying the child knew what he did was wrong, the judge weighed the severity of the crime versus whether the amount of abuse and neglect suffered by the boy played a significant role in the father's slaying.
Only 13 states have set a minimum age at which children can be tried or face adjudication in juvenile court, according to the National Juvenile Defender Center. In eight of those states, the age is 10.
New Mexico does not have any such law.
Terry A. Maroney, a Vanderbilt Law School professor who specializes in juvenile justice, said while such prosecutions are considered rare, it's hard to know exactly how many young children have faced or have been charged with first-degree murder since most of proceedings are typically sealed and laws vary by state. Those cases also are hard to prosecute because it's difficult to prove if the child "was too young to determine the finality of death, and if the child had the capacity to make moral decisions," Maroney said.
In the case of the 10-year-old New Mexico boy, prosecutors have opted not to try him as an adult.
"It's actually a good sign since no matter what charges he faces, he still will only be punished until he's 21" if he is found guilty, said Schwartz.
Cooley said the boy's defense team plans to call more than three dozen witnesses to testify on the boy's behalf about the abuse he faced and the failure by the state to intervene. He also said he'll be able to show that the boy did not fully grasp his actions that day and was exposed to constant violence. The boy's dad also kept loaded guns around the house, Cooley said.
Already, the defense team won a victory earlier this year when a state appeals court blocked prosecutor's attempt to force the boy's sister, then 6 years-old, to testify. Prosecutors say she saw the shooting.
But Cooley said that didn't matter. "Here you had a 250-pound man who liked to kick these kids around," Cooley said. "The state failed to protect them. That's the issue."