Former US police officer Mohamed Noor has been sentenced to 12-and-a-half years in jail for fatally shooting Australian woman Justine Damond Ruszczyk through the side of his police car.

Key points: Judge said Noor expressed remorse for the consequences of his actions but not the murder itself

Judge said Noor expressed remorse for the consequences of his actions but not the murder itself Ms Damond Ruszczyk's Australian family were not in court but had letters read on their behalf

Ms Damond Ruszczyk's Australian family were not in court but had letters read on their behalf The trial has tarnished the reputation of the Minneapolis Police Department

Noor was convicted of third degree murder and second degree manslaughter for killing Ms Damond Ruszczyk just minutes after she called 911 to report a possible sexual assault in the alley behind her Minneapolis home in July 2017.

Judge Kathryn Quaintance said the jury members who convicted Noor had asked when US police culture would change.

"Will there be changes? Change is needed," she said.

"Will some of the supervising officers be fired? Why should a civilian be afraid of approaching a squad car? What about the motto on the car to serve with compassion?"

Judge Quaintance also dismissed a defence motion to acquit Noor and set aside the jury verdict.

Sydney woman Justine Damond Ruszczyk was shot dead by then-policeman Mohamed Noor. ( Linkedin/ABC News )

Noor apologises to Justine's family

The judge said Noor had expressed remorse for the consequences of his actions but not the murder itself.

"He does not take personal responsibility for making an erroneous decision to fire a gun at her," she said.

"He has not acknowledged that he could have handled the situation in any other way."

Judge Quaintance noted that a large amount of money would be going to Australia as part of the $US20 million ($28 million) civil settlement, but said she hoped there would also be reform for locals.

Just before the sentencing, Noor stood before the judge and expressed remorse.

"I've thought and prayed about this for the last two years," Noor said.

"Neither of our families will ever be the same again. I have wanted to sit with Mr Damond and tell him about what happened and extend my condolences to him.

"I have owed Ms Ruszczyk's family an apology for a long time. I did write them a letter while in jail and now I apologise in-person for taking the life of such a perfect person who was dear to them and so many others."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 36 seconds 36 s I felt horror: Mohamed Noor speaks in court over Justine Damond Ruszczyk's death (Photo - AP, Leila Navidi/Star Tribune)

Fiance says he wishes he told her not to call police

Ms Damond Ruszczyk's American fiance Don Damond, who testified as a witness in Noor's trial, told the court in a five-minute-long statement that he could not convey the depth of his grief and trauma.

"How do I express the impact of the loss of my beloved, my dearest friend and my future wife to be?" he said.

"How do I sum up the pain and trauma of the last 23 months in this brief statement?"

He tried to do so by reading a letter to his beloved, weeping as he did so.

"I miss you so much. Every day, I don't understand how such a thing could happen," he said.

"You made my heart grow in ways I didn't think were possible. My heart aches every day."

Justine Damond Ruszczyk's fiance at court. ( Reuters: Craig Lassig )

Mr Damond apologised to Ms Damond Ruszczyk for selling the house in which they had shared so much love and laughter, but said he could not bear living in it anymore.

"I saw your wedding dress for the first time the week after you were murdered," he told the court.

He also revealed the couple had planned to travel to Egypt to try and conceive a child in the autumn of 2018.

He spoke of the pain of not being able to say goodbye and he wished he had not told her to call the police when she thought she heard a woman being sexually assaulted behind their home.

"You died surrounded by strangers, some of whom did not care about you a bit," he said.

"It was at my direction that you summoned your own death.

"I don't know that I'll ever love again."

Family scarred forever by Justine's death

Ms Damond Ruszczyk with her fiance and his son. ( Facebook: Don Miller Damond )

Ms Damond Ruszczyk's Australian family were not in court but attorneys read letters on their behalf.

They said their family had been scarred forever and many members were suffering from ongoing grief and mental health problems.

Family lawyer Bob Bennett read a statement on behalf of John Ruszczyk.

"I am a father who has lost his daughter in an unnecessary violent act," he said.

"It is as if I have lost a limb, a leg.

"She was doing what any Aussie girl would do; she was trying to help someone … this was an obscene act."

In his statement, Mr Ruszczyk demanded the maximum sentence for Noor.

Prosecutors Patrick Lofton and Amy Sweasy, who secured the first murder conviction against an on-duty Minnesota police officer, argued for the 150-month sentence Judge Quaintance imposed.

Noor silent as he left the court room

Noor's lawyers Tom Plunkett and Peter Wold had filed a court motion seeking no prison time in which they noted Noor "was never late for court".

They cited his remorse and noted Noor's background growing up in a refugee family.

Mr Plunkett said imprisoning Noor would not do anything to address the culture of fear that led to the shooting.

"The police are afraid of the people, the people are afraid of the police," Mr Plunkett said.

"The community is armed to the teeth. We need cultural change."

Mr Plunkett said if Noor was spared prison he could meet with the Damond and Ruszczyk families and fight for change.

Outside court, a large group of Somali Americans protested the verdict, calling it an aberration of justice and an attack on Muslim immigrants. The protest dispersed quickly and peacefully.

For his part, Noor did not say a word as he was led away from court to begin his sentence.

Case shocked Australia and rattled America

Justine Damond Ruszczyk and her American fiance Don Damond in 2015. ( Supplied )

The shooting of Ms Damond Ruszczyk cut short an Australian-American love story and highlighted differences between the two countries.

In Australia it seemed inexplicable — a woman fulfils her civic duty by calling police because she thinks someone is being raped only to end up dead herself.

"How can a woman out in the street in her pyjamas seeking assistance from the police be shot like that? It is a shocking killing," Australia's then-prime minister Malcolm Turnbull said.

The case was nowhere near as surprising to Americans, who are used to seeing roughly 1,000 deaths from police shootings a year.

Some of the most infamous shootings have occurred in the "Twin Cities", Minneapolis and Saint Paul, where the deaths often have racial undertones.

Black men disproportionately serve as the victims.

One of the most high-profile was school cook Philando Castile, who was shot and killed while reaching for his wallet at a traffic stop a few miles from central Minneapolis.

His girlfriend live-streamed the shooting as her child watched on. Mr Castile's police killer was acquitted on manslaughter charges.

Mr Castile's mother Valerie Castile told the ABC that more care went into Noor's trial than her son's, citing the lengthy jury selection in Noor's compared to her son's case.

Valerie Castile's son Philando was shot dead by a police officer in Minneapolis in 2016. ( ABC News: Niall Lenihan )

"One day. Poof. Just like that," she said, snapping her fingers.

"No-one cares. And in this case, it's been a week? Right is right and wrong is wrong. You do the math. You see it in other people who are down there in the court building, they see it as well."

Ms Castile said her heart went out to the Damond Ruszczyk family with whom she visited shortly after the shooting.

Prosecutors said police obstructed investigation efforts

Prosecutors complained about police efforts to obstruct their inquiry into Justine's shooting. ( The Star Tribune: Richard Tsong-Taatarii )

The court heard that officers at the scene shielded Noor from scrutiny.

Sergeant Shannon Barnette, the officer in charge of the scene, sent the car Noor fired from off to be washed before it had been completely examined.

She also turned off her body worn camera at the scene and told another officer that Ms Damond Ruszczyk was "probably a drunk or a drunk addict".

There is no hard proof of what was said between the two, but Sergeant Barnette told the court Noor's welfare, rather than the victim, was foremost in her mind.

"He asked me several times 'Sarge is she going to be OK?' I told him, I'm not going to worry about that right now: I'm going to worry about you," she told the court.

Prosecutors repeatedly complained about police efforts to obstruct their inquiry.

Members of the Minneapolis Police Department were reluctant to speak with police.

It was only when the prosecutors convened a grand jury in December 2018 that they could gain the crucial evidence they needed to bring Noor to trial.

As the trial was underway, the head of the local police union, Chief Bob Kroll, was warned that he faced contempt charges for observing the hearing in an overflow courtroom when he was listed as a witness.

Noor will serve time at a high-security prison

Noor himself spoke in his own defence in a surprise appearance.

"My intent was to stop the threat," Mohamed Noor told the court. ( AP: Cedric Hohnstadt )

That was the first time Ms Damond Ruszczyk's family were given an explanation by a man charged with upholding the law in Minnesota.

He told the court that he saw Ms Damond Ruszczyk as a threat to his and his partner's life. His counter-ambush training taught him to think quickly.

"Action is better than reaction," Mr Noor said.

"If you're reacting, that means it's too late to protect yourself … you die."

The trial has tarnished the reputation of the Minneapolis Police Department, which already saw its police chief resign over the incident.

Years of frustration at injustice mean minority groups, while sympathetic to Ms Damond Ruszczyk's family, are likely to continue to rage at what they see as a double standard.

Noor has returned to Oak Parks Height prison, one of the most secure prisons in the country.

Its exercise yard is ringed with officers with machine guns and no-one has ever escaped.

Due to the high security, it is known as a place where the worst offenders go — including some from interstate.

It also offers protection for targets for the prison population such as former police officer Noor.