Mills pleaded not guilty to all charges and was released on bail awaiting a jury trial.
He will reappear in court in November.
It comes after the Herald revealed this morning that Mills allegedly punched and kicked the head of a man he was trying to arrest, fracturing his eyesocket.
A spokeswoman for the Counties Manukau police declined to answer questions about the case as the matter was before the courts, other than to confirm the specific charges against the "former staff member".
The Herald understands the investigation started when a work colleague reported the officer to their supervisor after the arrest that later led to the common assault charge - the least serious of the alleged offences.
A wider review uncovered the two previous alleged acts of violence, for which the more serious charges were laid, which raises questions about how they were missed in the first place.
By law, police officers are allowed to use reasonable force "as may be necessary" in the execution of their duties - such as arrests - unless they can be carried out in a "less violent manner". Anyone, including police officers, can also use reasonable force in self-defence.
However, police policy sets out guidelines about the use of force and sets out tactical options, such as OC spray or Tasers, which are available to officers.
Officers are trained to make judgment calls to decide whether force is necessary compared with the level of threat and risk to themselves and the public.
The policy states any force must be "timely, proportionate and appropriate given the circumstances known at the time" and every effort must be made to minimise harm.
Ultimately the legal authority to use force comes from the law, not police policy.
There are 17 other officers before the courts on charges for alleged offences which occurred while on duty.
In one of those cases, a judge is weighing up whether to convict an officer who punched a handcuffed teenager in the head so hard that he broke a bone in his hand.
The arrested youth spat at him in the back of the police car and the officer, who has name suppression, used "distraction strikes" to push his head down.
"I just wasn't going to let him spit at me again, sir," the officer told Judge Raoul Neave. "My assessment of him was he was a drug-taker and there was no way I wanted to catch anything that he might have had."
Judge Neave has reserved his decision.
An Auckland officer who stamped at least twice on the head of a man resisting arrest was ruled to have gone too far in a recent Independent Police Conduct Authority report.
The officer claimed the burglary suspect might have been armed and he was trying to stop him from hurting himself.
That justification was "untenable" and the force used was simply to gain compliance, authority chairman Judge Sir David Carruthers said.
The officer was not charged and still works in the Auckland City police district.
