A mother sat two seats down from her 13-year-old son in a Jefferson Parish courtroom on Thursday, but she did not look at him.

She cried softly as a detective testified about how the boy beat his 5-year-old sister to death. She turned away from him entirely and put her head down in her lap when the detective added that her daughter, Viloude Lewis, had died in excruciating pain, allegedly at the hands of her own son.

Devalon Armstong, 13, is charged with second-degree murder in Viloude’s death last month.

The boy allegedly told the detective that he was practicing professional wresting moves he’d seen on television, with the 3-foot-tall child as his unwilling sparring partner. He slammed the child onto a bed and onto the floor, the detective testified. Then he allegedly beat her and jumped on her until her ribs were broken and her kidneys lacerated. She died from blunt force trauma and severe internal bleeding.

The boy, the detective said, smiled as he recalled his exploits.

His defense attorney questioned Armstrong’s mental competency shortly after his arrest, and the child was evaluated by a panel of court-appointed doctors. He was found competent to proceed to trial Thursday in Jefferson Parish Juvenile Court.

The juvenile courtroom is not set up like those in a traditional courthouse. The state’s juvenile justice system is meant to encourage rehabilitation, and the courtroom is designed to be less threatening and austere.

The judge sat on the bench, with a conference table before him. It was up to him on Thursday to decide whether prosecutors could prove enough probable cause to support the murder charge.

On one side of the table sat the prosecutor and the detective. The boy sat across from them, next to his attorney, shackled and staring blankly down at the table. His mother, Alourdes Desvallons, was two seats down, on the far end, with her pastor next to her for comfort.

She had been away at the store on a Sunday afternoon last month, and left Armstrong, the oldest of her three children, at home to care for the littlest.

By the time Jefferson Parish Sheriff’s deputies arrived around 1:30 p.m., the child was unresponsive on the bathroom floor. She was rushed to Ochsner Medical Center’s West Bank hospital, where she died a short time later.

There were no outward signs of injury, and her brother at first told detectives that she had complained of a stomachache and went upstairs to brush her teeth, Detective Matt Vasquez testified Thursday.

Later, the boy said, he found his sister on the floor and laid her on the sofa.

But when Vasquez went to the Coroner’s Office, which performed an autopsy the following morning, he learned that she’d suffered severe internal injuries, including broken ribs and a lacerated liver and kidneys. It was an agonizing death if the child was conscious, the coroner told him.

He went back to Armstrong, he testified, and asked for more answers.

The child then admitted, the detective said, that for 45 minutes that Sunday afternoon he had practiced moves he saw on “World Wrestling Entertainment,” a staged professional wresting program.

He allegedly told the detective that he picked the child up and slammed her into the ground.

The teen called those moves the “Mark Henry slam” and the “John Cena slam,” named after the wrestlers who made them famous.

Desvallons gasped as the detective described the maneuver: the boy picked the girl up in his arms “like a sack of flour.”

Then he dove onto the floor and the bed with the child beneath him. She allegedly told him he was hurting her, but he continued.

As the detective testified that the boy also confessed to punching his little sister between 20 and 30 times, Desvallons put her head on the table and wept.

His defense attorney argued that the action did not reach the level of murder.

Second-degree murder is defined in Louisiana as a killing done with “a specific intent to kill or to inflict great bodily harm.”

His attorney argued that there was no evidence that he intended to harm the child. She had no outward injuries that would indicate to him she was hurt.

It was, his attorney said, a “tragic accident.”

But the judge found that, even short of an intent to kill, the statute allows for a murder charge with an intent to seriously harm.

The judge found probable cause and ordered that the boy remain at the juvenile jail on a $100,000 bond. He is scheduled for another hearing next month.

If he is found guilty of murder, Armstrong could be sent to a juvenile facility until he is 21 years old.