At his murder trial last year a jury heard that Millane's death was accidental - a tragic but simple case of rough sex gone very wrong.
The jury later convicted him of murder.
Today he was sentenced to life in prison with a minimum non parole period of 17 years.
Outside court, Detective Inspector Scott Beard spoke to the media about the case.
He said the actions of the murderer - who still has name suppression - were "senseless and needless".
The man still maintains he is not guilty of murder.
"He can maintain his innocence, but the jury found him guilty," said Beard.
"I don't believe that rough sex should be a defence ... If people are going to use that as a defence, all it's going to do is revictimise the victim and their family."
White Ribbon said in a statement after the sentencing that the "rough sex defence" was an international issue and there is increasing pressure on Western governments worldwide to ban it.
White Ribbon Manager Rob McCann said: "In this type of defence, the defendant takes the focus off their own behaviour and encourages discussion of the victim's prior sexual history and preferences.
"This is an irrelevant distraction in a murder trial. They use the defence to blame the victim and it is totally unacceptable. There is no way of knowing what the victim wanted or said in this instance, and you simply cannot consent to being murdered.
"The idea that rough sex could result in accidental death is a fallacy. It takes considerable pressure to strangle someone and if a sexual partner loses consciousness for any reason during sex, the logical response would be stop and check they are ok.
"While engaging in sadomasochistic behaviours can be a valid choice for consenting adults, it comes with the responsibility to ensure the safety of your partner."
Earlier this week Beard sat down with the Herald to talk about the case.
He said sitting in court next to Millane's parents David and Gillian each day of the trial, listening to the defence case which included graphic details of their youngest child's sexual history and activity had been frustrating.
"Strangling someone for five to 10 minutes until they die, that's not rough sex - strangulation is murder," he said.
"And that's what the jury decided.
"It's disappointing when you have to sit next to the mother of Grace and hear the defence evidence, hear how they are portraying her daughter.
"It felt wrong for me, personally."
Beard said what the charge boiled down to was the strangulation - not Millane's sex life or intimate personal preferences.
"What was important was what happened when, from the time that grace and the killer went into the room to when he came out. What happened in there?
"Between those hours was all that mattered.
"I understand why a defence lawyer will do that (bring up a victim's personal life) - and will be allowed to do that. But essentially, you know, the jury had to decide what happened in that room.
"And they came back very quickly with murder. So they didn't for one moment ... believe that rough sex defence."
Beard said the defence in general was "a cop out".
"I understand from a defence perspective, they have a job to do as well. I understand it - but that doesn't necessarily sit well with me.
"As I say, I personally I think it's a cop out I think and in this case the jury saw through it."
This morning Justice Simon Moore said the murderer had portrayed "a numbness of the soul" and " depravity to a high degree" in killing Millane and disposing of her body.
Between the two acts he also took intimate photos of the dead woman, watched porn and searched various things on the internet like "hottest fire" and whether there were flesh-eating birds in New Zealand.
Justice Moore said the killer was cruel and callous.
He also addressed the defence in court.
The killer was represented by Ian Brookie, Ron Mansfield and Claire Farquhar.
Justice Moore said the defence Brookie put forward was entirely proper and was run in a "strong and competent fashion".
The level of public criticism Brookie received during the trial was "entirely wrong", he added.
