Joel and Ali played for opposing AFL teams. They had been playing a tough match and Joel was angry that Ali kept tackling him. Joel hit Ali in a head high tackle which gave Ali a mild concussion. Head high tackles are no longer permitted by the official rules of AFL games, but they are quite common. In response to the head high tackle, the referee, Emma, sent Joel off the field and came to check if Ali was okay. Ali was dazed and confused. He saw Emma looming over him and thought Emma was a player about to hit him, so he kicked Emma in the shins. Emma lost balance and fell forward with her arm outstretched, fracturing her wrist as she hit the ground. Discuss the criminal liability of Joel and Ali.