The family of Australian life coach Justine Damond Ruszczyk, who was shot dead by a Minneapolis police officer, will file a civil lawsuit in the US.

If successful, the lawsuit could result in a multimillion dollar payout to her family.

The family’s lawyer, Bob Bennett, a specialist in representing victims of police shootings in Minnesota, is expected to file the civil rights complaint in the US Federal Court in Minneapolis on Monday.

Ms Damond, 40, formerly of Sydney, was dressed in her pyjamas at her Minneapolis home just before midnight on July 15 last year when she heard what she feared was a woman being raped.

She called police and when a squad car arrived in an alley behind her house she approached it in the darkness.

Mohamed Noor, who is no longer a police officer, was allegedly sitting in the front passenger seat of the police vehicle, shot across his partner and out the window at Damond Ruszczyk.

The bullet hit her in the stomach and she died at the scene.

Noor has been charged with third-degree murder and second-degree manslaughter.

Ms Damond’s US fiance, Don Damond, and family and friends last week held vigils in Minneapolis and Sydney to commemorate the first anniversary of her death.

Mr Damond told the gathering in Minneapolis that the pain he has endured was unimaginable.

-AAP