Key Points:

A 12-year-old boy who shot his mother after a row about his refusal to do jobs in the house has been found guilty of premeditated murder.

Judge James Conlogue found the boy guilty in Cochise County Superior Court in the southern Arizona town of Bisbee on Friday.

The child's mother Sara Madrid, 34, who frequently slapped and cursed her son, left the family home with her boyfriend after he refused to do chores. The boy took a .22-calibre Ruger pistol from her bedroom closet, waited for his mother to return and shot her repeatedly.

Ms Madrid's boyfriend of 10 years, Alfonso Muooz, who helped raise the child, said he had taught him how to use the pistol for self-defence.

The boy was tried as a minor after the court heard evidence that Ms Madrid had verbally abused him for years. Ms Madrid did not want him living with her. Her sister testified that he is "a docile, sweet boy" and that "Sara said [the boy] was stupid".

The trial heard that after the last argument when Mr Muooz and Ms Madrid returned home, the boy was waiting for them in a parked vehicle in the driveway. Ms Madrid approached him and asked why he was not doing his jobs around the house. Mr Muooz said he heard noises like "firecrackers" and realised the boy had shot his mother. Mr Muooz told him to put down the gun and he did.

Prosecutors wanted the boy tried as an adult, but the judge ruled the case should remain in juvenile court. He is due to be sentenced on 23 January. Under Arizona law, the boy can be held only until he turns 18.