The investigation stems from an incident in January, in which Gibson allegedly hit his ex-girlfriend Oksana Grigorieva. The district attorney will now decide whether to file charges in the case.
Investigators are also looking into allegations Grigorieva tried to extort money from Gibson.
Grigorieva's relationship with Gibson became public after his wife of 28 years filed for divorce last year.
In the wake of a drunken driving arrest four years ago in Malibu, Gibson publicly apologized for an anti-Semitic tirade.