State Coroner Terry Ryan is investigating the Wieambilla shootings on December 12, 2022, which was preceded by NSW school principal Nathaniel Train, 47, illegally crossing into Queensland with a cache of firearms during a COVID border lockdown.
Train's wife is set to give evidence at the inquest on Thursday at the Brisbane Coroners Court.
The woman cannot be identified due to a court order handed down before the inquest hearings started.
Stacey, Gareth and Nathaniel Train were shot dead by specialist police. (HANDOUT/CORONERS COURT OF QUEENSLAND)
Nathaniel Train and his brother Gareth, 46, fatally shot police constables Matthew Arnold, 26, and Rachel McCrow, 29, when they arrived at a remote property west of Brisbane with two other junior officers to serve an arrest warrant.Â
The brothers also fatally shot their neighbour Alan Dare before specialist police killed them and Gareth Train's wife Stacey, 45, that night.
Nathaniel Train's wife is expected to testify about her observations of the behaviour of Gareth, Stacey and Nathaniel Train in the years and months before the shootout.
The woman is due to testify in particular about the missing person report she made concerning Nathaniel Train in December 2022 and the days between that report and the shootings.
Mr Ryan previously heard Nathaniel Train suffered a near-fatal heart attack in August 2021 and later left his successful career as a NSW primary school principal and left his wife without explanation to live at Gareth and Stacey Train's bush block property.
A forensic psychiatrist has previously testified the Trains likely suffered from a "shared psychotic disorder" with Gareth as the primary sufferer who acted on extreme religious beliefs and conspiracy theories.