A jury has begun deliberations in the trial of a former Minneapolis police officer accused of fatally shooting Australian Justine Ruszczyk while he was responding to a 911 call.

At issue in the trial is whether Mohamed Noor was justified in using deadly force when he shot the Australian-born woman who was in the United States for her wedding.

Noor, a 33-year-old Somali American, pleaded not guilty to second-degree murder, third-degree murder and second-degree manslaughter in the July 2017 shooting, which led to protests and the resignation of Minneapolis' police chief.

The jury began deliberating today after both sides delivered closing arguments.



Noor's lawyer, Thomas Plunkett, launched his closing by banging on his lectern, shouting a profanity and yelling, "Pow!"

Plunkett was recreating testimony by Noor that he heard a bang right before Ms Ruszczyk approached his car, followed by his partner swearing and struggling to pull out his gun. Noor said he saw Ms Ruszczyk raise her right arm before he fired.

"It's the perfect storm," Plunkett said.

He urged jurors to look at the precise moment of the shooting, without the benefit of hindsight, and consider whether a reasonable officer would do the same thing when confronted by the same factors.

"He acted as a reasonable police officer," Plunkett said.

Earlier, prosecutor Amy Sweasy attacked Noor's credibility and questioned his claim he and partner Matthew Harrity heard a loud noise that startled them just before a woman appeared at Harrity's window.

She noted neither Noor nor Harrity mentioned the bang at the scene, with Harrity first talking about it three days later in an interview with an investigator, and pointed out Ms Ruszczyk's fingerprints were not found on the car.

"There is no conclusive proof she ever touched that car," Sweasy said.

She also took issue with Noor's testimony he saw fear in Harrity's eyes as Ms Ruszczyk appeared at the window, that Harrity said "Oh Jesus!" and that Harrity was struggling to pull his gun when Noor fired.

"Whatever Harrity said or did, it was not a command for the defendant to shoot and kill Ms Ruszczyk," Sweasy said.

The night of the shooting

Authorities said Ms Ruszczyk called 911 on July 15, 2017, to report a possible sexual assault in an alley behind her house.

Officers Matthew Harrity and Noor were dispatched to the scene and arrived in a squad SUV at 11.37pm, according to a criminal complaint. At 11.40pm, Ms Ruszczyk was shot in the abdomen and died minutes later at the scene.

Harrity told investigators he heard a noise and was startled by a glimpse of a person coming up to the officers' SUV, the complaint states. Prosecutors said Noor, sitting in the passenger seat, pulled out his gun and shot across the vehicle to hit Ms Ruszczyk, who was outside the driver's side door.

Justine Ruszczyk's family. (Supplied)

In announcing the charges, Hennepin County Attorney Mike Freeman said Noor acted recklessly .

"There is no evidence that Officer Noor encountered a threat, appreciated a threat, investigated a threat, or confirmed a threat that justified the decision to use deadly force," Freeman said.

The officers were wearing body cameras but did not turn them on before the shooting, and the squad car camera did not capture the incident, investigators said.

The Minneapolis Police Department has since updated its body camera policy to direct officers to turn on their body cameras upon being dispatched to a scene.

Harrity identified Noor as the shooter, and testing of the bullet determined it was fired from Noor's gun, the complaint states.

In general, officers on trial for shootings are rarely convicted , partly because jurors tend to give police the benefit of the doubt about whether shootings are a legally justified use of force, experts say.

A former East Pittsburgh police officer was recently found not guilty in the fatal shooting of an unarmed teenager.

Noor expresses remorse

Ms Ruszczyk had travelled from her native Australia to Minneapolis to live with her fiancé. She was killed a month before her planned wedding.

She had trained as a veterinarian but then became a spiritual healer, yoga and meditation instructor and life coach, she said on her web page.

Noor came to the United States at a young age and became the first Somali American assigned to the Fifth Precinct, which covers Southwest Minneapolis. He joined the Minneapolis Police Department in March 2015.

He expressed condolences to Ms Ruszczyk's family in a statement through his lawyer shortly after the shooting.

Don Damond is comforted by friends and family after making a statement to the press near his home after Minneapolis police officer shot and killed his fiance Justine in 2007. (AAP)

“He takes these events very seriously because, for him, being a police officer is a calling,” the statement said.

“He joined the police force to serve the community and to protect the people he serves. Officer Noor is a caring person with a family he loves and he empathises with the loss others are experiencing.”

The trial

Two neighbours also testified they heard a sound that could have been the slapping of the squad car.

The testimony bolstered the defence's argument that the sound of Ms Ruszczyk slapping the squad car "caused Officer Noor to perceive her as a threat," defence attorney Marsh Halbeg told CNN affiliate WCCO.

Halberg has provided commentary on the trial for the station.

Testifying in his defence, Noor said he had "a fraction of a second to save his partner's life from what he called 'the threat,'" according to WCCO.

But the prosecution argued the slap didn't happen. An expert testified that "none of the 51 fingerprints found on the squad car" matched Ms Ruszczyk's.

A use of force expert testified that Noor's use of deadly force was "excessive and objectively unreasonable".

Being "startled" is different than "fearing death or great bodily harm," said Lt. Derrick Hacker of the Crystal Police Department.