Justine Damond grand jury set to begin

More than 30 police officers are expected to testify at the secret proceedings in Minneapolis.

A sign reads 'Justice for Justine' at a makeshift memorial for Justine Damond on July 18, 2017 in Minneapolis, Minnesota. Source: Getty

A grand jury probe into why Minneapolis Police Officer Mohamed Noor shot dead Australian life coach Justine Damond in a residential alley is set to begin.

The Minneapolis Star-Tribune reported more than 30 officers, including Officer Noor's partner Matthew Harrity, have been summoned to testify before the grand jury on Tuesday.

The secret proceedings will help prosecutors decide if Officer Noor will be charged with Ms Damond's death.

The majority of the officers subpoenaed are Officer Noor's trainers and police academy educators, according to Minneapolis Police Federation president Bob Kroll.

Justine Damond Ruszczyk was shot dead after calling 911 about a possible sexual assault. Source: AAP

Sydney-raised Ms Damond, 40, called 911 just before midnight on July 15 after hearing what she feared was a woman being sexually assaulted near her Minneapolis home.

When Officers Noor and Harrity arrived in the alley in their police vehicle Ms Damond approached in the darkness.

Officer Noor, in the passenger seat, shot across Officer Harrity, in the driver's seat, and struck Ms Damond fatally in the stomach, according to Minnesota's Bureau of Criminal Apprehension.