Mohamed Noor shot Justine Damond last July in the Midwestern city of Minneapolis after she called police to report a possible rape. She was shot as she approached the police car that arrived to investigate.
Noor has been charged with third-degree murder and second-degree manslaughter, which respectively carry sentences of up to 25 years and up to 10 years in prison.
In a court filing Wednesday, Noor's attorneys disclosed that he would plead not guilty and claim self-defence and the use of reasonable force. A court hearing is scheduled for May 8.
Authorities allege Noor shot Damond in the abdomen from the passenger seat of a police cruiser as she approached the driver's side window when the car neared the end of a dark alley behind her home.
The two officers in the car had been startled moments before by a sudden sound.
Damond, who had twice called police with concerns of a potential sexual assault in the alley, died at the scene.
When charging Noor in March, prosecutor Mike Freeman said "there is no evidence that Officer Noor encountered a threat... that justified his decision to use deadly force."
Noor's attorney Tom Plunkett released a statement at the time claiming his client had "acted as he has been trained and consistent with established departmental policy."
The shooting provoked outrage in the United States and in Damond's native Australia.
Damond had moved to the US to marry her American fiancee, Don Damond, whose name she had already legally adopted. Her maiden name was Ruszczyk.
The 40-year-old's Australian relatives and the country's prime minister demanded answers -- and protests in Minneapolis led to the resignation of the city's police chief.
