FRESNO, Calif. (KFSN) -- Xander Villalobos lost his biological father to cancer in 2020.
Aaron Moton stepped into the "Dad" role when he dated and lived with Xander's mother, Nikkey Rojas.
But Moton had a misdemeanor domestic violence conviction and Rojas says anger management classes didn't stop his temper from intruding in their relationship.
"We were in the bathroom, we were arguing, he put me against the wall and he choked me," Moton said.
Rojas didn't report the incident.
Four months later, in October 2021, she says Moton was taking care of Xander when she noticed her son had gone limp.
Three days shy of the boy's third birthday, she was on the phone with 911.
"I remember her saying, 'I don't understand. I don't understand. He was just fine and now I don't understand.' says Ryan Rockwell with Fresno police. "She was just panicking and you could hear Xander moaning."
Coroners determined Xander later died from a completely lacerated liver. He also suffered injuries to his head and spinal cord.
Coroners said those deadly injuries occurred in the two hours before Xander arrived at the hospital.
Rockwell says Moton didn't admit to causing the injuries but in a follow-up interview, the 23-year-old gave a possible explanation.
"He told me that he shook Xander really hard and said that the reason he didn't tell me this is because he was concerned this may have caused his death," he said.
Rockwell tried to get Moton to take a lie detector test, but Moton never did it.
But the detective found Moton had searched YouTube for how to defeat a polygraph.
His defense attorney pointed out that Rojas submitted to a lie detector test and it concluded some of her answers were "deceptive."
A judge will decide Wednesday whether there's enough evidence to hold Moton for a trial, a trial that could lead to him getting 25 years to life in prison.