Nathaniel Train, 47, suffered a heart attack and had to be resuscitated 16 months before he took part in the shootings in December 12, 2022 that resulted in the deaths of six people at a remote property at Wieambilla, west of Brisbane.
State Coroner Terry Ryan on Tuesday heard from consultant neurologist Professor Christian Gericke as to whether Train suffered ongoing brain damage from a lack of oxygen during cardiac arrest and if this had affected his behaviour or caused psychosis.
Professor Christian Gericke said Nathaniel Train had no brain damage from his cardiac arrest. (Jono Searle/AAP PHOTOS)
Following his heart attack, Train abandoned his successful teaching career and illegally crossed the NSW-Queensland border during COVID lockdowns with a cache of firearms to live with his brother Gareth, 46, and sibling's wife Stacey, 45, on their remote bushland block.
Prof Gericke said he had reviewed Nathaniel Train's medical records and found "positive evidence" to disprove he did not have an enduring brain injury following his cardiac arrest.
"There is very good evidence (Train) did not suffer from this," he said.
Prof Gericke said Train was given a CT scan after his heart attack and it did not show brain damage.
The Train brothers concealed themselves along their driveway and fatally shot Police Constables Matthew Arnold, 26, and Rachel McCrow, 29, without warning.
The constables had joined two other junior officers to serve an arrest warrant on Nathaniel Train.
The brothers also fatally shot their neighbour Alan Dare before specialist police killed all three Trains later that night.
The Train brothers shot dead two constables and a neighbour. (HANDOUT/CORONERS COURT OF QUEENSLAND)
Prof Gericke said "large parts" of Nathaniel Train's brain were available to test at his autopsy, which offered the most accurate results for physical signs of damage from lack of oxygen, referred to medically as hypoxic ischemic encephalopathy (HIE).
"There was no damage ... except for the bullet. That caused some damage," Prof Gericke said.
Prof Gericke said he had seen thousands of patients with HIE and they had profound symptoms that doctors had not observed in Nathaniel Train.Â
Mr Ryan heard medical records suggested Train had a rapid recovery after his heart attack with minor memory issues but his cognitive scores were within normal range.
Prof Gericke said Train had symptoms of delusional disorder even before his heart attack and there was a strong case for him having a genetic predisposition to psychosis given his brother also suffered from the same mental illness.
A barrister for a Train family member asked Prof Gericke if a heart attack without HIE could still have pushed Nathaniel Train toward paranoid or delusional thinking through shock and trauma of nearly dying.
"On the spectrum of probabilities ... psychotic illness is still more likely," Prof Gericke said.
Mr Ryan also heard on Tuesday from Deakin University's Associate Professor of Politics, Professor Josh Roose, about his expert report identifying the political, religious and ideological influences that shaped the actions of the Trains.
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