Following a sentencing indication hearing in January, Judge Andree Wiltens indicated home detention depended on a positive pre-sentence report "but it seems to me that effectively serving a one-year sentence of imprisonment at home, having paid reparation to these victims, would meet the situation here in terms of the purposes and principles of sentencing."
The judge took into account Mills' early guilty pleas, previous clean criminal record, his remorse, a split in his family, the loss of his reputation and career, as well as the offer of $10,000 reparation to the victims.
This brought the total end sentence to two years of imprisonment - which is the maximum sentence available to be converted to one year of home detention.
Mills' will serve his home detention at an address which is permanently suppressed out of fears for his safety.
"The aggravating factors, as I say, is that you were a serving police officer and the serious assault on the third male involving not only an attack to the head, but the fact that they were all defenceless lying prone on the ground, while one 15-year-old boy was being held by two of your colleagues," said Judge Andree Wiltens.
Speaking on behalf of Mills, barrister Todd Simmonds told the Herald that his client had acknowledged his wrongdoing and offered to meet personally with the victims to apologise in person.
Mills was genuinely remorseful for his offending, said Mr Simmonds and extended those' "sincere apologies to the victims, the community and his former police colleagues."
Mills first came under investigation in April last year when he "immediately and without warning" kicked a suspected car thief in the face.
The 23-year-old was lying on the ground trying to hide from police when Mills kicked and punched him in the head, fracturing his eyesocket, in a violent assault caught on camera by the Eagle helicopter hovering above.
An investigation into the attack uncovered two earlier cases including another occasion when Mills kicked a prone suspect, a 15-year-old boy, in the face despite the teenager already being restrained by fellow officers.
In the first assault, Mills was alone when he tackled another 15-year-old boy to the ground and punched him in the head two or three times.
All three attacks happened in Manurewa, in the Counties Manukau police district, between February and April last year.
When interviewed by police investigators about the complaints, before his guilty plea, Mills said two of the three suspects were resisting arrest and force was necessary.
In regards to the third victim, the 15-year-old restrained by other officers, Mills said he ran too close to his head and accidentally stomped on him. It was not a kick, he said.
By law, police officers are allowed to use reasonable force "as may be necessary" in the execution of their duties such as arrests. 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 pepper 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.
Police Association president Greg O'Connor has previously said the case disproved the "myth of police going easy on their own".
"We work in a goldfish bowl. If anything like this happens, it's often reported by fellow officers, robustly investigated and put before the courts."
Superintendent John Tims, the Counties Manukau district commander, said it is always very disappointing when any staff member is before the courts but it demonstrates that Police are not afraid to hold its staff to account.
"I am appalled at Mr Mills' actions, which are not reflective of the attitude of the thousands of other Police men and women who come to work each day to make our communities safer, and I applaud those staff who spoke up and raised their concerns so they could be investigated," said Mr Tims.
"All such issues are treated very seriously and investigated robustly - and as is evidenced by this case, those responsible are put before the courts where appropriate and held to account the same as anyone else."
"The public can have every confidence that Police does not tolerate criminal behaviour amongst its staff, and anyone proven to have committed an offence can expect to face the consequences."
Mr Tims said police conducted a thorough and robust inquiry into three separate incidents which took place while Mills was on-duty between February 22 and April 21 last year.
The first complaint was laid against Mills on April 19 by other police staff and an investigation was launched by the Counties Manukau Police Professional Conduct team.
Mr Mills was stood down on April 24 pending the outcome of the investigation, but did not carry out any further work with Police from April 21 before resigning in July 2015.
Abuse of power
Common assault
February 22, 2015: Mills investigates report of wilful damage at the Manurewa train station. Accuses a 15-year-old boy of the crime and tackles him, before punching him in the head several times.
Injures with intent
April 19, 2015: Fifteen-year-old boy arrested for stealing a car. He was lying face down on the road when Mills ran towards him and kicked him in the head without warning. The teenager needed medical treatment for swelling and bruising.
Causing grievous bodily harm
April 21, 2015: A 23-year-old man who stole a car was lying under a tree to avoid being found by police, but was found by the Eagle helicopter, which alerted Mills. Without warning, the officer kicked the man in the face and fractured an eye socket. The victim needs surgery.
