Koia and a passenger were on their way to visit Phillips when the incident occurred about 11pm on Friday, June 16, last year.
It was not known why but in an unusual feature of the case Phillips is believed to have been lying prone on Cobden Street near the intersection with Waitangi Street, about 200 metres from her home.
She was fatally injured after Koia ran her over.
Koia thought she had run over debris.
Statements read in court by some of Phillips' family relayed their despair at the protracted court process and Koia's delayed guilty plea, which they felt showed a lack of remorse by her and disrespect to their family.
Phillips had a husband, three young children, a tight-knit wider whanau and a wide circle of friends.
Three of her five siblings were based overseas at the time of her death and rushed back to New Zealand — one alone on a long-haul flight.
Phillips' brother told the court Koia's sentence could be nothing short of imprisonment given their family's devastating loss.
As the lesser penalty to be imposed on her became obvious, some of Phillips' family and friends left the courtroom.
Others waited until the end of the sentencing to voice their disapproval, one woman yelling, "do you mean she's not going to jail? That b**** should be jailed".
At the time of the incident, Koia was in breach of her learner licence — driving without her corrective lenses and without supervision of a fully-licensed driver.
She had a blood-alcohol level 26 milligrams above the legal limit.
She stopped after she realised she ran something over and joined police and ambulance staff at the scene, who were called by residents who heard the collision.
Paramedics could not save Phillips, who died there.
Judge Cathcart prefaced the sentencing by saying the courts were bound by the facts presented to them.
A sentencing judge did not make up his or her view in a case of this nature. The factual matrix was worked out by the Crown and defence counsel after a long investigation.
He accepted this investigation had delayed Koia's guilty plea and the family's anger and frustration about that.
But it was correctly pursued by counsel Amanda Courtney as part of her duty of care to her client.
The unusual feature of Phillips' lying prone on the road needed to be explored.
Often being informed of the true facts gave people insight as to how a case must be dealt with. He was regrettably familiar with these types of cases and relevant case law, including the United Kingdom case of Cooksley in which the English courts helpfully set out factors to determine culpability where facts could be so variable.
The judge also noted recent legislative changes in New Zealand, resulting in significantly higher maximum penalties for crimes of this type.
Crown prosecutor Jo Rielly sought a starting point between two-and-a-half and three years imprisonment.
Courtney submitted it should be lower. The overall circumstances reflected a momentary inattention and vision and visibility impairment.
Judge Cathcart set the starting point at 2.5 years. He allowed discounts for mitigating circumstances — four months for Koia's lack of previous criminal convictions, and one month for remorse.
Despite the family's view, documentation proved Koia's remorse throughout and her continued willingness to attend restorative justice should Ms Phillips' family ever change their minds, the judge said.
Courtney said Koia was severely psychologically impacted by the death and the effect of it. These were people she knew and loved.
There was further discount of five months for Koia's youth and other personal circumstances. Her actions that night were indeed akin to youthful impulse and lacked the foresight of a mature person, the judge said.
The Crown did not contest the 20 percent discount — the equivalent of four months, —for guilty pleas.
It was appropriate to convert the final sentence of 16 months imprisonment to home detention as the least restrictive outcome, Judge Cathcart said.
