Harris last month told The Salt Lake Tribune that the Oct. 6 incident was an accident that occurred when one player knocked another out of bounds and straight into his chest.
Harris said he put up his arms to protect himself from the player. Video of the incident shows everybody around Harris also throwing up their arms to avoid injury, he said.
"It's what happens in football," Harris said. "All of a sudden there's a football helmet in your chest that is coming [at you] 20 mph. It's what happens at other sporting events. Players run into players. Players run into spectators."
Harris was acting as assistant coach during his son's Maple Mountaineers game against the Payson team. The two teams were tied when a Payson running back began moving the ball to the end zone for what would have been a tie-breaking touchdown. As the boy ran close against the field's boundary lines, authorities allege Harris stepped into the boy's path and raised his forearms, hitting the boy under the chin.
Court records state the teen suffered a concussion.
But Harris said the teen popped right back up and continued to play the rest of the game. He said there was no medical break needed, and that trained medical personnel also witnessed the incident and have since told him they didn't notice anything in the teen's behavior that would have indicated he suffered a serious head injury.
Harris' attorney, Rhome Zabriskie, has said the case boils down to whether the city can prove Harris intended to injure the boy. Zabriskie said the collision was an accident and not criminal in nature.
ABC News presented this story of the football game in early November, when Nathan Harris was charged (with video of the collision).