The gun accidentally went off at the school in February 2012 as the boy reached into the backpack, critically injuring fellow student Amina Kocer-Bowman.
The boy told investigators he had taken the gun off a dresser at the man's home. He said there were other unsecured firearms in the Allyn home of Douglas Bauer, a statement police confirmed during a search of the home.
Bauer is charged with third-degree assault in the shooting. Defense attorney Wayne Fricke has argued that the case shouldn't proceed, because Bauer did nothing to cause the assault.
Kitsap County Deputy Prosecutor Jeremy Morris has said that if the third-grader hadn't had "unfettered access" to firearms, the shooting at Armin Jahr Elementary in Bremerton wouldn't have happened. Fricke argued that allowing the case to proceed could set a dangerous precedent.
The Kitsap Sun reported that appeals court judges Joel Penoyar and Jill M. Johanson voted to allow the charge against Bauer to proceed. Courts are able to discern the difference between allowing a child access to, for example, a butcher knife or a hand grenade, they wrote in the decision released Friday.
The viability of such cases would be evaluated on whether the parents' actions were "at least a gross deviation from a normally careful person's conduct," the judges wrote.
"We are told that this decision will open the floodgates to charges against innocent parents for the unanticipated criminal acts of their children where the parents' only fault was in failing to totally secure an item that could potentially be dangerous," the judges wrote. "We do not anticipate such a flood."
Retired judge C.C. Bridgewater, a guest on the panel that heard oral arguments in the November appeal, dissented.
"Even in the face of tragedy, this is a case involving potential criminal liability and imprisonment," he wrote. "As such, we are bound to strictly construe the law, not to stretch it to fit the exigencies of the situation."
Bauer will appeal the ruling to the state Supreme Court, Fricke said. If the Supreme Court doesn't overturn Friday's decision, the case will return to Kitsap County Superior Court for a jury trial.
State law says someone whose criminal negligence "causes bodily harm to another person by means of a weapon or other instrument" is guilty of third-degree assault." If convicted of the felony Bauer faces a possible maximum of five years in prison and would be prohibited from owning firearms.
Kocer-Bowman underwent multiple surgeries. The bullet from the shooting remains lodged in her spine.
The outcome of the Bauer case has ramifications for other cases pending around the state, including that of the 3-year-old who shot himself in the head after finding a gun in a car at a Tacoma service station. The boy was riding with his mother and the gun owner, who were charged with manslaughter.