After the video was released, Johnson recused herself from the case, and another prosecutor indicted the murder suspects. Johnson lost her bid for re-election last November.
Johnson was charged with obstruction of a police officer and violating her oath of office. She could not immediately be reached for comment.
In a statement issued by her office when the investigation started, Johnson's office said: "We are confident that any investigation will show that our office acted appropriately under the circumstances."
The statement added: "There is a public misconception about this case due to false allegations against our office by those with an agenda."
The former police officer, Gregory McMichael, 65, his son Travis McMichael, 35, and William "Roddie" Bryan, 51, are each charged with felony murder, federal hate crimes and other charges in Arbery's death. All have pleaded not guilty and are set to go to trial in October.