Lawyers for ex-officer Mohamed Noor argue in motions filed on Wednesday that the charges should be dropped because of prosecutorial misconduct and lack of probable cause.

Noor is charged with third-degree murder and second-degree manslaughter in the July 15, 2017, death of Damond, a 40-year-old life coach.

She was killed after calling 911 to report a possible sexual assault.

Prosecutors say Noor was in a squad car's passenger seat when he shot Damond through the driver's side window after she approached the police car.

Noor's lawyers argue Hennepin County Attorney Mike Freeman's statements about the case "have undermined Officer Noor's fundamental right to a fair trial."

"The Hennepin County Attorney's statements in this case are irresponsible, inexcusable and rise to a level of professional misconduct that cheats citizens out of a fair trial," they wrote in their filings.

The defence says Freeman told a group of activists in a recorded conversation in December, before Noor was charged, that he didn't have enough evidence yet, investigators "haven't done their job" and having enough evidence would be "the big present I'd like to see under the Christmas tree."

"His comments are not merely racially and culturally insensitive - they are full of animosity. They mock due process. They deny due process," the attorneys argue.

32-year-old Noor has since been fired from the police force.

Noor's lawyers also argued that the third-degree murder charge does not meet the "depraved mind" standard under Minnesota law.

Noor's partner the night of the shooting, Officer Matthew Harrity, said both he and Noor "got spooked" when Damond approached their car, and that Harrity feared for his life.

Harrity, who was driving, said he heard a voice and a thump on the back of the car, and glimpsed a person's head and shoulders outside his window.

Noor fired through the open driver's side window, fatally shooting Damond in the abdomen.

Prosecutors contend Noor acted recklessly and was not justified in using deadly force. But the defence contends Noor's actions "were the product of a split second reaction."

Australian Associated Press