What is Child Abuse according to the state of California?

The Penal Code (P.C.) defines child abuse as: “a physical injury inflicted by other than accidental means on a child by another person.” It also includes emotional abuse, sexual abuse, neglect, or abuse in out-of-home care. Child abuse does not include a “mutual affray between minors,” “reasonable and necessary force used by a peace officer” under specified circumstances, or spanking that is reasonable and age appropriate and does not expose the child to risk of serious injury.
(P.C. 11165.6, Welfare and Institutions Code (W&IC) Section 300.)