Former Minneapolis police officer Mohamed Noor has formally pleaded not guilty to murder and manslaughter charges over the shooting death of Australian woman Justine Damond Ruszczyk.

Key points: Mr Noor confirmed his expected not guilty plea on self-defence grounds in a pre-trial hearing

Mr Noor confirmed his expected not guilty plea on self-defence grounds in a pre-trial hearing Judge Quaintance ruled prosecutors could not point to prior "bad acts" that happened when Mr Noor was a police officer

Judge Quaintance ruled prosecutors could not point to prior "bad acts" that happened when Mr Noor was a police officer The trial is scheduled to begin early next month

Mr Noor, 33, confirmed his expected not guilty plea on self-defence grounds to two murder charges and one manslaughter charge during a pre-trial hearing in Minneapolis.

Judge Kathryn Quaintance also ruled that prosecutors could not use Mr Noor's prior acts as a police officer against him, including pointing a gun at a motorist during a traffic stop.

Ms Damond Ruszczyk had called police to report a possible sexual assault happening in an alley behind her Minneapolis home but was shot as she approached Mr Noor and his partner's patrol vehicle. She was unarmed.

Mr Noor refused to talk to investigators when he was offered a chance to do a voluntary interview, and prosecutors wanted to use that as evidence.

They argued in court documents that the situation would have been different if Mr Noor was arrested and had chosen then to invoke his right against self-incrimination.

Justine Damond Ruszczyk was shot after calling police to report a possible sexual assault near her home. ( AP: Aaron Lavinsky/Star Tribune )

But Judge Quaintance disagreed, saying: "It seems to me the right not to incriminate oneself is a pretty seminal constitutional right."

Judge Quaintance also rejected prosecutors' bid to use a 2015 psychological test of Mr Noor before his hiring as a Minneapolis officer.

The test found Mr Noor was disinterested in interacting with others and, when compared with other officers, was more likely to be impatient or have difficulty confronting people. A psychiatrist concluded that overall Mr Noor was fit to be a police officer, saying the test results don't carry much weight.

Judge Quaintance said prosecutors could not make the exam or Mr Noor's silence a central part of their case but may be able to bring it up if he testifies.

Marsh Halberg, a Minneapolis defence attorney who is not connected to the case, said those rulings raise the stakes for Mr Noor if he chooses to testify.

Justine Damond Ruszczyk was pronounced dead in the alley at the south end of her block. ( The Star Tribune: Pat Pheifer )

Mr Halberg said tactically it makes sense to have Mr Noor remain silent until trial and have him tell his story to everyone for the first time in front of jury. But if these other issues can come up during his testimony, he has to be prepared for that.

Judge Quaintance also ruled prosecutors could not point to prior "bad acts" that happened when Mr Noor was a police officer, including one incident in which prosecutors say he pointed a gun at a motorist's head two months before Ms Damond Ruszczyk's shooting.

However, she said, prosecutors could introduce evidence about a 911 call that Mr Noor and his partner responded to less than two hours before Ms Damond Ruszczyk's shooting. In that case, police were called to the same neighbourhood about an elderly woman who seemed to be lost or confused.

Judge Quaintance said that evidence is relevant to what Mr Noor knew and to his state-of-mind on the night of the shooting.

Mr Noor's partner the night of the shooting, Matthew Harrity, told investigators he was startled by a loud noise right before Ms Damond Ruszczyk approached the driver's-side window of their police SUV.

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According to the criminal complaint, Mr Harrity, who was driving, heard a voice and a thump and caught a glimpse of a person's head and shoulders outside his window.

He then heard a sound like a lightbulb breaking, saw a flash and looked to his right to see Mr Noor in the passenger seat with his arm extended. He looked out his window and saw Ms Damond Ruszczyk with a gunshot wound.

Mr Noor was fired from the police force after being charged.

The trial will begin early next month and Mr Noor remains free on bail.

Ms Damond Ruszczyk was a 40-year-old life coach and dual Australian-US citizen who had been living in Minnesota with her fiance for more than two years.

Her Sydney-based father, John Ruszczyk, has filed a $US50 million ($70 million) civil rights lawsuit against Mr Noor, the city and others. That case has been put on hold while the criminal case proceeds.

ABC/Wires