Australia and the United States have been waiting almost two years for a firsthand account of Justine Damond Ruszczyk's shocking killing.

In July 2017, Minneapolis Police officer Mohamed Noor shot an unarmed, pyjama-clad Australian woman asking for help.

The months without a full explanation have compounded the family's grief and eroded the public's trust.

But the trial is inching toward a close.

Today's testimony from Mr Noor's partner, Matthew Harrity, brought both some answers and a pivotal turning point.

Harrity delivers damaging inconsistency

Dressed in his police uniform and sporting a light beard, Mr Harrity took off his hat, sat in the dock and recalled life with his former partner.

"I loved working with Officer Noor," he told the court, noting that the two trusted each other completely.

Officer Matthew Harrity said with the information he had, it would have been premature to use deadly force. ( AP/Star Tribune: Leila Navidi )

The two men have not spoken since.

Mr Harrity painted a picture of two men who thought their lives were on the line in the seconds before Mr Noor shot Ms Damond Ruszczyk.

He said he heard a noise on his side of the car. He said he'd never been so scared, and he yelled either "oh Jesus" or "oh shit".

"In this situation with the thump … I went straight to [thinking] this could've been a possible ambush … I was thinking of my safety," he told the court.

He had an answer ready for why his initial explanation, captured on body camera, had not mentioned the thump.

"I was just giving a brief, vague public safety statement on what happened. I wasn't explaining the details," he said.

In a major inconsistency for the defence, he could not say how the phrase "she slapped the car" ended up in a search warrant used for entering Ms Damond Ruszczyk's home.

Near the end of the five-hour testimony, Mr Harrity was pressed in a rapid series of questions from Prosecutor Amy Sweasy.

It is not yet known if Mohamed Noor will testify at the trial. ( Linkedin/ABC News )

She asked why he did not also fire his weapon.

Mr Harrity said he was still analysing the situation and, without seeing any weapons or hands, he was not sure whether Ms Damond Ruszczyk's silhouette at the window was a target or a threat.

The decisive question from Ms Sweasy was whether "a use of deadly force at that point would've been premature".

"Yes, with what I had," Mr Harrity answered.

If Mr Noor does not testify, the jury will have no direct insight as to why the officer saw a threat that warranted risking a human life.

Distressing footage shows the end of a life

The court also played the body camera footage from Mr Harrity and Mr Noor.

The two turned the cameras on immediately after the shooting. The video is the most distressing material yet shown in the trial.

The video shows Ms Damond Ruszczyk battling for breath as Mr Harrity performs CPR.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 17 seconds 2 m 17 s Why was Justine Damond Ruszczyk shot?

He appears in control and barks orders at Mr Noor to calm down and assist as the officer wanders around.

Later, Mr Noor himself provides CPR, with Mr Harrity instructing him to slow down while wrestling with a bandage.

Ms Damond Ruszczyk was declared dead by paramedics at the scene shortly after.

As the video played in court, Ms Damond Ruszczyk's father John put his hand to his head as her stepmother sobbed next to him.

Mr Harrity told the court that the trauma still affected him to this day, with the immediate aftermath especially acute.

He shed tears in the courtroom.

"I could sit and stare at a blank TV … nothing's on the TV, and I could sit and stare at it," he said.

"My wife could be talking to me for five minutes straight. She'd have to yell at me before I could even answer."

Officers show their close ranks

Mr Harrity's damaging admission had to be dragged from him, but he emerged with more credibility than other police witnesses.

Their troubling testimony brought accusations of special treatment.

Crucial early explanations were not recorded because police shielded Mr Noor and ensured recording devices were turned off.

One of the first officers to approach Mr Noor after the shooting, Jesse Lopez, said: "Mo [Mr Noor], hang on. We gotta shut [the recording device] off. Alright kiddo? You alright?"

Mr Noor answered, "yeah".

"Just keep to yourself. Keep your mouth shut until you have to say anything to anybody," Mr Lopez continued.

Sergeant Sharon Barnette, the supervising officer, said her main concern when she spoke to Mr Noor was his comfort. She also turned off her body camera.

"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."

A previous witness testified Ms Barnette had said the shooting victim was "probably a drunk or a drug addict".

But not all officers were so supportive

In what felt like something of a pattern, more senior officers expressed scepticism than those on patrol.

It was the homicide chief, Lieutenant Richard Zimmerman, who attributed the drunk quote to Ms Barnette. His testimony suggests he was unimpressed with efforts at the scene.

"I was just looking at the body to see if there was any weapon there … my first thought, frankly, was what the f***? Why isn't there anything there?"

Only when the homicide department got involved did it dawn on the on-scene officers that Ms Damond Ruszczyk was the same person who called 911 because she feared a sexual assault was occurring outside her house.

Mr Zimmerman noted how crucial those early hours are in an investigation.

"Sometimes witnesses or evidence not collected or found has a way of disappearing," he said.

The Damond and Ruszczyk families sat through these allegations of a compromised investigation.

They were just metres away from Mr Noor. In the extremely cramped courtroom, they regularly brushed shoulders with his family and supporters.

The evidence of a poor investigation has been interspersed with increasingly graphic footage capturing her death.

One exhibit showed her blood-stained, pink T-shirt. It bore a pink koala and bullet holes.

Ms Damond Ruszczyk's fiance, Don Damond, told the court that he had once promised his future wife they would someday live in Sydney, where gun laws are a world away from America's.

Ms Damond Ruszczyk had agreed she'd live in America for a while first after hearing that Mr Damond's adult son was upset about the pending move.

This time, the Ruszczyk family, including her American-born father, made the long journey across the hemisphere, hopeful of justice at last.

Another family is waiting too

Mr Noor's family was also sitting just metres away.

They are Somali refugees who fled violence in the hope of a new life in America.

Every day, Mr Noor's father arrives to support his son, often joined by his wife, mother and others.

His defence counsel occasionally reached across the short wall separating the gallery from the court to offer a hand or a smile. They frequently placed an arm on Mr Noor's shoulder as he listened to the evidence.

Lawyers Peter Wold and Tom Plunkett have painted a picture of a tragic accident — an officer using justified force because he feared for his partner's life.

And just metres away from Mr Noor, the families, the lawyers and the judge are yet another group: the 12 members of the jury who will decide which of those explanations they accept.

The ramifications of that decision will be felt deeply across one city, two families and three continents.