Joseph and Sonya Smith beat their son Josef and then locked him in a wooden box and confined him to a closet for hours at a time before he died.
Josef died from blows to the head, and firefighters who responded to the family's 911 calls said his body was covered with bruises.
The couple's defence case was based that their son did not die from the injuries, and that crucial tests were not performed that would have found the actual cause of their boy's death. Their biggest claim was that Josef passed out and never regained consciousness after the family gathered in the kitchen to participate in a prayer session with their church via the Internet.
Joseph Smith acknowledged hitting the boy "four or five times," and told police his son frequently needed discipline because the child carved death threats on the walls and claimed to be a "soldier of the devil.
The boy would have been 12 friday, prosecutor Eleanor Dixon said. In her closing argument Wednesday, she sang "Happy Birthday" to the dead boy, leaving the defendants in tears.
The Smiths were also convicted of involuntary manslaughter, cruelty, aggravated assault, reckless conduct and false imprisonment.
