The 4-year-old son of Alexis Dixon died after suffering a variety of injuries doctors said were more consistent with being in a car crash than, as Dixon claimed, falling inside the family's travel trailer.

The boy's death was no accident, a Kern County sheriff's investigator told Dixon during an interview about two weeks after Mark Allen Dixon's death in 2010. He accused her of losing her temper and injuring the boy.

Dixon, 31, remained calm, according to redacted sheriff's reports that recently became available in court. She tilted her head back, stared at the ceiling and started laughing.

"I have no problem going away for the rest of my life for my son, because of the fact that I was in charge of taking care of him," she said. "But I will never, ever, ever be OK with saying that I physically hurt my son and caused his death."

The investigator thought Dixon's behavior strange because she laughed when being questioned about the recent death of a child and she didn't deny hurting the boy.

That interview was conducted on May 10, 2010. But it was not until March that Dixon was arrested and charged with murder in her son's death, with her next hearing scheduled for April 15.

The court filings don't indicate why it took so long to charge Dixon. Authorities have previously said tissue studies were necessary, and pathologists needed to determine what injuries were caused by the alleged abuse and which were the result of doctors' efforts to save the boy.

The reports say Alexis Dixon and the child's father, also named Mark Dixon, both used methamphetamine. Alexis Dixon admitted to using meth just a few days before her son's death.

Alexis Dixon told investigators she'd been using meth since she was 13 years old, the reports say. She had four children, two with Mark Dixon.

Her first baby tested positive for meth and was taken by Child Protective Services, the reports say. Dixon failed to stay clean, and the baby was adopted.

The reports say she told investigators her relationship with her husband had been "terrible" for more than a year. She said he had no interest in her or the children, and left her alone with them while out drinking.

She told investigators she didn't know how her son was injured on April 23, 2010. The reports say she told investigators she was napping while her husband was out cleaning a drain on the property. She awoke to a loud thud in another room of the trailer.

She got up to investigate and found Mark on the floor, according to the reports. She tried to get him to stand up, but he kept crumpling to the floor. She thought he was faking, and ran cold water over him.

The boy still didn't move. Investigators asked if she shook him to try to get a reaction. She said she probably did.

She walked outside holding the boy, falling as she did. She then placed Mark against a brick wall while she called for her husband, the court filings say she told investigators.

The boy slid down the wall and hit his head on a pole, according to Dixon's interview. Mark was taken to Kern Medical Center, then Children's Hospital Central California in Madera, where he died the next day.

Neighbors told investigators that Dixon showed no emotion after finding the boy unresponsive, the reports say. But the father, they said, was beside himself when he saw the condition his son was in.

Mark Dixon told investigators he prayed to God to take him instead when doctors told him his son would die, the reports say. He lay by his son's side until the boy died.

The reports say he told investigators his children were the best thing to ever happen to him. They asked what was the worst thing to ever happen to him.

"This," he replied.