"Methamphetamine was my drug of choice," she told the court.
She said she couldn't remember how much alcohol she would drink, but that it would be Jim Beam. She thought she'd drink a bottle in a night, probably about once a week.
The boy's mother cried as she told of how she was in an abusive relationship and that her partner was in and out of prison. He was in a gang, she said, and that the accused would often tag along with his father to things that gang would do.
"It wasn't good, but I allowed it," she told the court. "I blame myself for living that lifestyle."
She would hide a lot of the drug-use and violence from her mum, she said. But her mother always knew, she said, and she would take the kids away.
The boy's grandmother also has name suppression.
"A lot of drugs were going on there. They didn't do it around me, but I could tell," she told the court, testifying as a second witness for the defence.
She made the family move in next door so she could keep an eye on the kids.
"They were the neighbours from hell," she said, recalling a time the boy's father dragged her daughter from her home by the hair.
"I would take the boys," she said. "I would take them with me. I'd just say to them, 'get in the car', and we would go."
The defence has called a third witness, a psychiatrist Dr Craig Immelman, who specialises in children and adolescents. He's testifying to the boy's cognitive abilities, which the defence says weren't properly developed through his young life.
"You will hear that [the accused's] childhood development was not normal and his cognitive ability is not what you'd expect for a 12-year-old," said defence lawyer Philip Hamlin.
The court has already heard about the mental state of the boy's co-accused. The defence for the other boy, a 14-year-old accused of murdering Mr Kumar, wrapped up with the testimony of a child neuropsychologist yesterday.
