Prosecutors argued the boy, now 12, knew what he was doing when he shot 32-year-old Jeff Hall - a regional leader of the National Socialist Movement - and the slaying was premeditated.
Defense attorney Matthew Hardy said his client grew up in an abusive and violent environment and learned it was acceptable to kill people who were a threat. Hardy contended the boy thought if he shot his dad, the violence would end.
The boy, who is not being identified by The Associated Press because of his age, did not testify at trial.
Riverside Superior Court Judge Jean Leonard heard the case without a jury. At issue was whether the boy knew what he was doing was wrong and whether there was premeditation.
Prosecutors argued that the child killed his father to keep him from splitting up with his stepmother, who at first said she had killed Hall but then quickly retracted her statement. She was not charged in the case.
The boy's younger sister bolstered the prosecution's case by saying her elder sibling plotted the shooting days in advance.
Hall was shot at point-blank range with a .357 Magnum while he slept on a sofa in the family home.
The boy said in a videotaped interview with police that he didn't think he'd get in trouble because he saw an episode of "Criminal Minds" in which a child killed an abusive father and wasn't arrested.
Prosecutors maintained Hall's white supremacist beliefs had nothing to do with the crime. They noted the boy had a history of violence that dated back to kindergarten when he stabbed a teacher with a pencil.
Hardy said he hopes the boy, if convicted, would not be sent to a juvenile lockup but rather be placed in a private facility that offers therapy, medical treatment and schooling.