Minneapolis: A police officer who fatally shot Australian life coach Justine Ruszczyk Damond outsider her home believed he and his police partner were in a "classic ambush scenario", a Minnesota court has heard.

The trial of Mohamed Noor, the officer who fatally shot Damond in 2017, began in Minneapolis on Tuesday, local time, with opening statements from the prosecution and defence.

Prosecutors have charged Noor, 33, with two counts of murder and one of manslaughter.

If found guilty, Noor will be the first police officer in Minnesota's history to be sent to jail for killing a civilian.